Y9 Yearly Science Notes 2024 PDF

YEARLY SCIENCE REVISION NOTES The Immune System Pathogens: Microbes and other microscopic agents that cause diseases are known as pathogens. Diseases that are caused by pathogens are known as infectious diseases. For example: - Food poisoning - The common cold - Measles - COVID-19 Type of Pathogen Bacteria Viruses Fungi Example Salmonella, a cause Influenza virus, cause Microsporum, cause of food poisoning of the flu of athlete's foot Unicellular or Unicellular Neither (Not living) Unicellular or multicellular Multicellular (both) Cells Small simple cells Not cells Completes cells but with no nucleus cannot photosynthesise Causes diseases Sucking nutrients Viruses enter cells The fungi feed off the by: after attacking a cell. and reproduce in host; some of them Some produce toxins them causing them to produce toxins pop then after that they spread throughout the body Similarities vs difference of Virus and Bacteria: Similarities: - Both are pathogens - Both can only be seen with a microscope - They both attach to cells Differences: - Some bacteria is good but all viruses are bad - Bacteria is unicellular where as viruses are neither - Bacteria are small simple cells but viruses are not cells Viruses are considered pathogens but NOT microbes as microbes are only living things and viruses are not living Difference Between Contagious and Non-contagious diseases: A contagious disease is a disease that can be spread. You can catch contagious diseases from people through transmission such as them coughing on you or you touching a surface that an infected person has also touched. COMPARISON: Contagious: - Come from microbes and microscopic agents - Some forms of these microscopic agents can be bacteria, fungi and viruses Non-contagious: - They come from vector-borne diseases. - Vectors are living organisms but are bigger than microorganisms and microagents. A lot of them are bugs such as mosquitoes Difference Between Infectious and Non-infectious diseases: The difference between infectious and non-infectious diseases are that infectious diseases are caused by pathogens. It can be both contagious and non-contagious. Non-Infectious diseases are non-contagious and are NOT caused by a pathogen. COMPARISON: Infectious: - Defined as any disease that is caused by pathogens - They can be both contagious and non-contagious. Non-infectious: They are caused by things such as: - Genetics - Nutrition/Diet - Lifestyle/Environment EXAMPLES: Infectious: - COVID-19 - Common cold - The flu Non-infectious: - Heart disease - Cancer - Diabetes The 3 Lines of Defence: The First Line Of Defence: Barriers to prevent infection such as the skin. The Second Line Of Defence: General responses to specific pathogens. The Third Line Of Defence: Immunity against specific pathogens. First Line Of Defence: Physical barriers Skin: - The skin acts as an effective barrier against most pathogens- unless its broken by a cut or graze Urine: - Flushes pathogen out of the body Cilia: - Cilia are microscopic hairs on the cells that line the airway in the lungs - Cilia move back and forth, pushing mucus and trapped pathogens out of the airways Chemical barriers Stomach Acid: - Not only aids digestion but it also kills many of the pathogens we swallow before they can cause an infection. Tears, Saliva and Mucus: - Traps pathogens so they can be flushed from the body or swallowed What are Physical And Chemical Barriers?: Physical barriers stop pathogens from entering the body by blocking or trapping them. Examples include skin and mucus. Some physical barriers, like cilia, actively push pathogens out. Chemical barriers kill pathogens before they can enter the body. They include stomach acid as well as enzymes in tears, saliva and mucus. Examples of Physical and Chemical Barriers: Physical Barriers: - Skin - Mucus - Saliva - Urine Chemical Barriers: - Stomach Acid - Mucus - Saliva - Tears Second Line of Defence: The second line of defence is general responses to infections. Some of these responses include: - Fever An increase of body temperature of 38 degrees celsius to try and kill pathogens through heat. It is usually accompanied by shivering or fever - Inflammation Pain or swelling around a specific part of the body. It is usually caused because more blood, filled with white blood cells, is being regulated towards that part of the body. - Phagocytes A specialised type of white blood cell that kills/absorbs anything that it doesn’t recognise as the body's own cells. Third Line of Defence: - The third line of defence is specialised weapons and responses used to eradicate disease from the body, unlike the second line of defence which is just general responses. - The third line of defence has 2 main roles: Identify and destroy specific pathogens Build long-lasting immunity against the pathogens in case they infect the body again How the Third Line Works: 1. The first time you encounter a pathogen, the third line of defence takes a few days to take action. In these few days you’ll you may feel sick 2. The third line of defence takes time because it needs to identify the pathogen first. To do this, it relies on specialised white blood cells called B cells 3. Next the B cells travel the bloodstream trying to identify and lookout for the pathogens. Each B cells carries a special protein called antibodies which it carries on it’s cell membrane 4. These antibodies bind onto the markers on the pathogens to identify them. Each type of pathogen has a unique type of marker. This means they can only bind to antibodies with a matching shape - similar to a lock and key 5. Once an antibody binds to a pathogen, the B cell releases millions of matching antibodies into the body to fight the pathogen and the B cell itself also clones itself 6. After the infection has been defeated, some of the B cells stay in the blood as memory cells along with any other leftover antibodies and together these form your immune system's memory of the pathogen. 7. If you’re infected with the same pathogen again, the third line of defence will respond faster and stronger than it did the first time. It works so fast you don’t even get sick meaning you become immune to the disease. The black wrench shape is the antibodies and the orange is the pathogens. The antibody is trying to bind onto a pathogen, in diagram 1 it works as the antibody and the pathogens marker shape matches but in diagram 2 it does not work as the antibody and the pathogen marker shape does not match. Vaccinations: Vaccinations are a type of treatment that helps the body build immunity against a disease (mostly) before or even after you have encountered it. They can be given through a syringe that is injected into the arm or other parts of the body, but some can also be given by nasal spray or mouth. Vaccinations work by introducing a dead or weakened pathogen into the body in a vaccine. This allows the immune system to identify the pathogen and develop weapons to fight it. The weakened form of the pathogen isn’t harmful as it can’t multiply or cause disease. Vaccination relies on the immune system's third line of defence. When a vaccine introduces a new pathogen: 1. B cells with matching antibodies bind to unique markers on the pathogen 2. After binding, the B cells produce antibodies and memory cells. These remain as a memory of the pathogen to help fight it quicker if the body gets infected by it again. The antibodies and memory cells are weapons that target the pathogens. This means that the immune system is prepared to attack if the pathogen ever shows up again. So vaccination helps the body if the pathogen ever shows up again. So vaccination helps the body build immunity in the same way as if it were infected but without the symptoms or disease Herd Immunity: Getting vaccinated protects you by boosting your immunity to an infectious disease. But it also helps protect your entire community. When enough people are vaccinated, the disease can’t spread in that community. This protects vulnerable people who can’t be vaccinated like children or the elderly. This protection they get from the community is called herd immunity. The diagram below shows how herd immunity works Homeostasis: Homeostasis is when conditions inside the human body remain fairly constant despite changes in the external environment. Negative feedback: 1. A change in the body is detected, for example a change in temperature. 2. A message is sent to a gland or organ (sometimes this is a multistep process). 3. A response is initiated. The response returns the body to its normal state. Glossary: Antibody: A protein that can identify and fight a specific pathogen. They are produced by B cells B cell: A white blood cell that produces proteins to attack pathogens. It cleans itself after it finds an antibody. Bacterium: A simple, single-celled microbe without a nucleus. An example of this would be E.coli that causes disease by attaching cells and releasing toxins. Chemical barrier: A defence that kills pathogens before they can enter the body. Some examples of this would be stomach acid or saliva and tears. Cilia:Microscopic hairs on cells that line the airways. Cilia pushes out mucus and trapped pathogens from airways and the lungs. Contagious Disease: A medical condition that can spread from one person to another by a pathogen. An example of this would be measles which is classified as highly contagious as it can spread to up to 18 people. Disease: A medical condition with specific symptoms. Diseases can be infectious like chickenpox or non-infectious such as cancer. Fever: An increase in core body temperature over an extended time. It helps to fight an infection by slowing or killing pathogens with high temperatures. First Line of Defence: Barriers that prevent pathogens from entering the body. Skin, saliva and urine and tears are all barriers. Fungus: An organism with complex cells that feed off a living host. Some fungi can feed off dead skin between the feet and toes causing athlete's foot (a disease). Herd Immunity: The protection from infection provided when most of a population is immune. Herd immunity protects vulnerable people like children as their immune system has not been fully developed or the elderly as their immune system has been extremely weakened. Immune System: The body system that prevents and fights disease. Immunity: An invasion of the body by pathogens that then multiply. The body can build up immunity by fighting off an infection or getting vaccinated. Infection: The body’s ability to protect itself from infection. Pathogens can infect the body through the eyes, the mouth, the body or cuts. Infection Rate: The percentage of unvaccinated people who become infected with a disease. A high infection rate occurs when the vaccination rate is very low. Infectious Disease: A medical condition that is caused by a pathogen. Chicken pox and the flu are all examples of infectious diseases. Inflammation: A painful redness or swelling of part of the body. Inflammation occurs when blood flow brings white blood cells to fight invading pathogens. Memory Cell: A b cell that remains in the bloodstream to recognise pathogens. Memory cells provide long term immunity by responding to diseases they have already fought stronger and faster than before. Microbe: An organism that is too small to be seen with the naked eye. Microbes include bacteria and some types of fungi. Mucus: A sticky liquid that lines the throat, lungs and intestines. Snot is the mucus produced by a special membrane in the nose. Negative Feedback Loop: A change in a system that causes another change in the opposite direction. During a fever, negative feedback loops work to keep body temperatures within narrow limits. Non-contagious Disease: A medical condition that cannot spread from person to person. For example the yellow fever virus passes from mosquitoes to people but cannot spread from person to person. Non-infectious: A medical condition that is not caused by a pathogen. Diabetes and asthma are non-infectious diseases. Pathogen: A microscopic organism or agent that causes disease. An example of this would be E.coli bacteria and the measles. Phagocyte: A white blood cell that engulfs and destroys pathogens. Phagocytes help infections by engulfing and breaking down viruses and bacteria. Physical Barrier: A type of defense that blocks or traps pathogens before they can enter the body. An example of this is the skin or mucus. Second Line of Defence: General responses to pathogens inside the body. This includes fever, inflammation and phagocytes. Third Line of Defence: Specific responses to specific pathogens inside the body that builds immunity. The third line of defence includes B cells, immunity and antibodies. Vaccination: A treatment that helps build immunity to an infectious disease. Most vaccines are given by injection but they can also be given by mouth or a nasal spray. Vaccination Rate: The percentage of a population that is vaccinated against a disease. A high vaccination rate can provide herd immunity by preventing a disease from spreading to vulnerable people. Vaccine: A substance that boosts the body's immunity to a specific pathogen. Vaccines can be made from dead or weakened pathogens and can cause the body to make new antibodies. Virus: A microscopic infection agent made of genetic material and proteins. Chickenpox is caused by a virus that reproduces inside cells and can spread from skin sores. White Blood Cell: A component of blood that fights infections. Phagocytes, B cells and memory cells are types of specialised white blood cells. Ecosystems The Problem With Plastic Production: Plastics may be very useful but they are also very dangerous. They end up in seas polluting them and killing wildlife and do not decompose for a very long time meaning that they don’t get absorbed into the Earth in a natural way. How do plastics end up in the ocean? Some of these ways include: 1. Litter from the city streets is washed through storm water drains into rivers and streams 2. Small plastics from washing machines can pass through sewage treatment plants 3. Waste from rubbish bins and landfill sites are blown or thrown away 4. Finishing nets and lines are lost or discarded from fishing boats/ships Once plastic has reached the ocean it can be carried around the world by winds and ocean currents. Eventually it might be washed up on a remote tropical beach or on a coastline in Antarctica. For this reason, pollution is a global problem and it can’t be stopped by one country alone, instead the whole globe has to contribute A lot of plastics in the ocean, trapped in large circular currents. The largest is located in North America and is known as the Great Pacific Garbage Patch. It is estimated to collect 8 trillion pieces of plastic that all together weigh 80,000 tonnes. What Are Plastics?: All plastics are made with the same general process and have the same general chemical structure. How Plastics Are Made 1. Crude oil is pumped out of the ground 2. The crude oil is separated into different liquids and gases 3. Small molecules are joined to form long chains 4. The new material is melted and moulded into the shape of choice The History of Plastic: ❖ In 1855, scientist Alexander Parkes invented the first plastic ❖ In 1909, scientist Leo Baekeland creates a new substance by accident called bakelite which creates new applications for plastics ❖ In 1950, plastics are used to make a huge number of “disposable” products ❖ In 1970, scientists first study the harms of plastic pollution Reducing Plastic Impact There are many ways of reducing your plastic impact. An easy way to go about this problem is to remember the 6 R’s of sustainability. ★ Refuse: Don’t use plastics that you don’t need ★ Re-use: Use a plastic item more than once instead of throwing it away instantly after use ★ Re-think: Consider alternatives like bringing a metal water bottle instead of buying a plastic one ★ Repair: Fix a plastic object like a chair or a toy instead of buying another one ★ Reduce: Cut down on your overall plastic usage ★ Recycle: Correctly throw away a plastic object so it can be made into another item instead of going to landfill What Are Ecosystems? All living things need the energy to survive. Producers like plants get their energy from sunlight whereas consumers like animals and us humans get energy from consuming producers or other animals. So one way that living things interact is to eat and get eaten. These interactions between animals and plants are shown in food webs and ecosystems. Ecosystems and Biotic and Abiotic Factors: Ecosystems are a collection of living things that interact with their physical environment. - Abiotic: All non-living aspects in the environment - Biotic: A living aspects of things in the environment - Examples of Abiotic Factors: Sand, sunlight, water - Examples of Biotic Factors: Sea snail, sea anemone Ecosystems have a wide range of scales. They can be as large as a rainforest or as small as a rockpool. As long as there are living things interacting with each other. An ecosystem can also form part of a larger ecosystem. For example: A small rock pool makes up a larger coastal ecosystem. Living things in an ecosystem is called a “biotic” factor. The etymology of the word (where the word came from) is from the greek word “bio” meaning life. Some examples of biotic factors in ecosystems include plants, animals and bacteria. Non-living things that are present in an ecosystem are called “abiotic” factors. The prefix “a'' means not and “bio” means living so “abiotic” means not living. A biotic factors in an ecosystem include the rocks, water, sunlight, temperatures and sea/ ocean currents. Differences Between Land and Marine Ecosystems: Land and marine ecosystems are very different in things other than whether they are on land or underwater. All of the biotic factors have adapted to life underwater. For example fish have developed gills to get oxygen while staying underwater. Yet there are also many similarities like producers underwater need sunlight for photosynthesis so plants don’t grow under 200 feet under the ocean as sunlight can not reach that far down. Photosynthesis converts the sun’s energy into stored energy in sugars that can then provide food for consumers. On land the most common producers that are found are plants whereas underwater this important role is carried out by algae Algae are a diverse group of organisms that include: - Seaweed: A large multicellular organism that looks like a plant or multiple plants - Phytoplankton: Microscopic organisms that float near the surface - Algae in coral: Microscopic organisms that live inside the tissues of coral, that provide them with sugars in return for a safe place to stay. Another difference between land and marine ecosystems is the surrounding sea water. The properties of seawater vary from place to place. The properties of seawater vary from place to place and water depth. The survival of many different organisms depends on: - Water temperature - The amount of salt dissolved in the water or salinity - The amount of acid, as measured with the pH scale – a pH of 7 is neutral, less than 7 is acidic and greater than 7 is basic, or alkaline Coral reef systems are very sensitive to these conditions and they grow best with: - A water temperature of 23-29 degrees - A salinity of 32-40 parts per thousand (ppt) - A pH of 8.4-8.6 Predator-prey Relationships: Unlike producers like plants who get their energy from photosynthesis, consumers need to eat other organisms to survive and when they eat an organism the energy is transferred. This transfer of energy is shown in food chains and food webs. In this type of relationship one organism hunts and eats another organism. This is known as a predator-prey relationship. The organism that is eating the other is called the predator and the organism being eaten or hunted is the prey. Competition There are more types of relationships in ecosystems other than predator-prey relationships. An example of this is competition. Competition is animals of the same or different species competing for mates, food, shelter or other resources as there is usually a lack of resources in an ecosystem. Competition is not only in animals though, plants also compete which each other for spots so that they can receive more sunlight. Some examples of competition would be “2 lions fighting over prey” or “10 camels drinking from the same watering hole in the desert Symbiosis: Organisms of different species often live side by side, interacting with each other over long periods of time. When at least one of these organisms benefits from this relationship it is called symbiosis or a symbiotic relationship. There are 3 major types of symbiosis: ➔ Mutualism or a Mutualistic Relationship is when both species benefit ➔ Commensalism or a Commensal Relationship is when one species benefits and the other isn’t affected ➔ Parasitism or a Parasitic Relationship is when one species benefits and the other is harmed Examples: Mutualism: The pistol shrimp and the goby as the pistol shrimp digs into the sand but shares its little room with the goby which helps protect it as the pistol shrimp is blind. In this way both of them benefit Commensalism: The emperor shrimp and the nudibranch as the emperor shrimp takes a seat on a nudibranch or sea slug and the sea slug is not bothered by this but the emperor shrimp gets a free ride and ends up picking up food scraps along the way Parasitism: Tongue eating louse and Red snapper because the tongue eating louse enters through the gills and then slowly sucks blood from it and slowly eats up its tongue. Here the tongue eating louse benefits whereas the red snapper is being harmed and does not benefit Energy Transfer Food is needed by organisms because it provides: matter to grow and repair our bodies energy to power our bodily functions and activities Consider the lettuce in a hamburger. The lettuce is made up of matter because it has mass and takes up space. It is made up of atoms that join together to form molecules. The compounds it contains include water, sugars, fats and proteins. The cells in our bodies are made out of similar types of molecules to the cells in the lettuce. This is why we can use the matter in the lettuce for growth and repair. Molecules in the bodies of organisms also store energy. You might have heard sugary foods being described as high in energy. This is because sugar molecules store energy that can be easily used by the body. The energy is needed so we can move, grow and function. Energy is also lost. For producers it is lost through photosynthesis whereas for consumers it is lost through moving, the excretion of faeces or other body waste (pooping) and also through cellular respiration. Only the energy that is stored in the animal's body is transferred to the next animal in the food chain and the higher you go the less energy is transferred so animals at the top need to eat more The Carbon Cycle: As with energy, organisms need a constant supply of matter just to stay alive. But unlike energy, matter isn't supplied by the Sun. The amount of matter on Earth doesn't change so it needs to be recycled. Remember that an ecosystem is a collection of living things that interact with each other and with their nonliving environment. The cycling of matter in an ecosystem depends on these interactions between organisms and their environment, including air, water and soil. Carbon is an example of an element that cycles through ecosystems. For example, it exists in air as carbon dioxide gas and in living things as carbon compounds, including sugars, fats and proteins. The continual movement of carbon through ecosystems is called the carbon cycle. DIAGRAM: Human Impacts: Human activities can have widespread effects on ecosystems because organisms rely on one another to survive. For example, there must be enough producers to support the consumers that feed on them. A change in the population, or number, of one type of organism is likely to change the populations of other organisms in the food web. For example, an oil spill could cause the population of corals in a reef ecosystem to decrease. This would cause a decrease in the populations of consumers, such as angelfish, that depend on the corals for food. This then might trigger a food shortage up the food chain. Human Activity 1: Fishing Fishing is an important source of food for many people around the world. In fact, around 3 billion people rely on fish as their main source of protein. Low levels of fishing don't have a big impact on a marine ecosystem. The fish are able to reproduce quickly enough to maintain healthy population numbers. In contrast, high levels of fishing can cause sharp drops in fish numbers. When fish are removed from an ecosystem faster than they can reproduce, this is called overfishing. Human Activity 2: Agricultural Runoff The science of growing crops and farming animals is known as agriculture. Humans have relied on farming as a food source for thousands of years. Although it takes place on land, agriculture can still affect marine ecosystems. Most farmers use fertilisers with extra nutrients in them to help plants grow. Following rainfall, any unused nutrients are washed into rivers and carried to the ocean. This is called agricultural runoff. Once in the ocean, the nutrients promote the growth of seaweed and phytoplankton. A sharp increase in the amount of phytoplankton is called an algal bloom. Large areas of water can turn green, blocking sunlight to other organisms and causing other harmful effects. Human Activity 3: Plastic Pollution Plastic waste is making its way into the ocean and having a range of impacts on marine ecosystems. There are two groups of plastic that can have quite different impacts on an ecosystem: Larger pieces of plastic can be mistaken for food. When ingested, they can cause starvation in larger animals, such as turtles, whales and seabirds. They can also cause animals to become entangled or die of suffocation. Pieces of plastic smaller than 5 mm are called microplastics. They can be ingested even by small animals, such as corals and crabs. They may affect the growth and functioning of these animals. Microplastics also damage the symbiotic relationship between coral and algae. This increases the risk of coral bleaching and death. It's important to note that there's still a lot we don't know about the impacts of plastic pollution. For example, we know that humans are eating fish that contain microplastics, but we still don't know how that affects us. A lot of scientific research is underway to improve our understanding of this issue. Energy Conservation The law of conservation of energy ENERGY CAN NEITHER BE CREATED NOR DESTROYED – ONLY TRANSFERRED OR TRANSFORMED. Forms of energy: Energy comes in many forms. Familiar examples include sound, light and electrical energy. Sound energy is heard when a wolf howls. Light energy can be seen when a lamp illuminates a room. Electrical energy travels through electrical wires such as power lines. Another form of energy that we experience in daily life is heat. For example, heat from the Sun warms your face on a sunny day. Scientists often refer to this form of energy as thermal energy. Even very cold objects, such as ice, have some thermal energy. Kinetic energy Any moving object has energy, including a speeding car, a rolling ball and a swaying tree. Scientists call the energy of movement kinetic energy. The faster an object moves, the more kinetic energy it has. Potential energy Not all energy involves a movement or action. Sometimes energy can be stored for later. This is called potential energy. Potential energy comes in different forms, including: ➔ Gravitational potential energy Gravitaional emergy is the energy stored in an object that is held above a centre of mass of a gravitational field. Usually, we measure this as height above the Earth’s surface. The higher an object is lifted in gravitational field, the more gravitational potential energy is stored. Gravitational potential energy can be transformed into kinetic energy and vice versa. For example, releasing an object from a height and allowing it to fall. ➔ Elastic potential energy Elastic potential eergy is energy stored in an object due to a force that temporarily changes its shape, such as squashing or stretching. ➔ Chemical potential energy Chemical potential energy is the energy stored in the chemical bonds of a substance. What is energy? Energy explains how objects change or move. For example, energy is needed to pull the rope in a tug of war. Scientists define energy as the ability to do work. But they don't mean our ordinary idea of work, such as school work or office work. In science, work occurs whenever a force causes movement. Examples of work in action include a person pushing a door open, a rocket blasting off into space and a leaf falling from a tree. Note: the word "energy" comes from the Greek prefix "en-" meaning in and "ergos" meaning work. So "energy" literally means in work. The units of energy Our bodies need energy to do work. Food acts as the fuel. Food labels tell you how much energy your body will gain from eating that food. The standard unit for measuring energy is the joule (J). You can calculate the number of joules it takes to ride your bike or play your favourite song through a speaker. A joule is a very small amount of energy. It is roughly the amount needed to lift an apple 1 metre off the ground. Sometimes a larger unit is needed. Food labels often use the kilojoule (kJ), which is equal to 1000 joules. 1 kJ = 1000 J To convert from joules to kilojoules, simply divide by 1000. All types of energy are measured in joules (J), but are calculated using different equations: - Gravitational potential energy (E ) is calculated using the equation: E =mgh Where m=mass of the object, g= strength of the gravitational field and h= height of the object above the mass it will fall to. - Kinetic energy (Eₖ) is calculated using the equation Eₖ= ½ mv², where m=mass of the object and v=velocity of the object. Energy transfer and transformation In general, energy can never be created or destroyed. However, it can pass from one object to another and it can also change forms. Energy can pass from one object or place to another without changing form. This is called energy transfer. Examples include: A soccer player kicks a ball, transferring kinetic energy from their foot to the ball. Power lines transfer electrical energy from a power plant to your home. Energy can also change from one form to another. This is called energy transformation. Examples include: An iron transforms electrical energy into thermal energy, or heat. A solar panel transforms light energy into electrical energy. Note: Further examples: Magnitude In physics, magnitude is defined simply as “distance or quantity.” It depicts the absolute or relative direction or size in which an object moves in the sense of motion. It is used to express the size or scope of something. In physics, magnitude generally refers to distance or quantity. Hydropower plants The electricity produced by a power plant isn't magically created out of nothing. The electrical energy always comes from a different form of energy. In the case of a hydropower plant, this is the kinetic energy of moving water. The power of moving water is obvious when you see and hear a thundering waterfall. Water at the top of a waterfall has more gravitational potential energy compared to water at the bottom. The higher the waterfall, the more gravitational potential energy is stored. As the water falls, the energy is transformed into kinetic energy. A hydropower plant takes this one step further. It transforms some of the kinetic energy of moving water into electrical energy! However, most hydropower plants these days aren't built near natural waterfalls. Instead, they depend on a dam built across a river. The production of electricity involves five key steps: 1. Water builds up behind the dam wall, storing gravitational potential energy. 2. Water flows down through a tunnel in the dam wall. 3. The flowing water spins the blades of a turbine. 4. The turbine is connected to a generator that transforms the spinning motion into electrical energy. 5. This energy passes through power lines to homes and factories. Diagram: Is all energy useful? The energy supplied to a device is called the input energy. In the case of the laptop, this is electrical energy supplied through a power cord. The energy that comes out of a device is called the output energy. A laptop transforms the input energy into three main forms of output energy: light, sound and heat. Not all output energy is useful. The purpose of a laptop isn't to warm your lap. So the heat produced by a laptop is wasted. Any output energy that is not put to the intended use is called waste energy. Output energy that is put to the intended use is called useful energy. All energy transformations produce some forms of energy that are not useful. Common forms of waste energy include heat and sound. Energy efficiency: Waste energy is a big problem. The more energy wasted by a device, the more energy we need to supply. That means higher running costs or needing to recharge the device more often. If the energy is supplied by fossil fuels, it could also mean a bigger contribution to climate change. For any device or process, we can calculate how much of the input energy is transformed into useful energy. This is called energy efficiency. Engineers often calculate the efficiency of the devices they design. If the device isn't very efficient, they can change their design to improve it. Energy efficiency is calculated by dividing the useful output energy by the total input energy. Multiplying the result by 100 gives the efficiency as a percentage: For example, imagine you have a kettle with an efficiency of 80%. That means that 80% of the input energy is transformed into useful energy. The rest of the output energy – 20% – is wasted. Glossary: Chemical potential energy: Energy stored by chemical bonds Elastic potential energy: Energy stored when an object is compressed, stretched or twisted Electrical energy: Energy that passes through an electric circuit Energy: The ability to do work Energy efficiency: A measure of how much of the input energy is useful energy Energy transfer: The passing of energy from one object or place to another Energy transformation: The conversion of energy from one form to another Flow diagram: A model that shows how energy is transferred and transformed Gravitational potential energy: Energy stored when an object is raised above the ground Heat: Energy that can be felt as warmth Input energy: Energy supplied to a device Joule: The standard unit of energy Kilojoule: A unit of energy equal to 1000 joules Kinetic energy: Energy of movement Light: Energy that can be seen Linear relationship: A relationship that produces a straight line on a graph Mass: The amount of matter in an object or substance Model: A representation of an object, process or system Non-linear relationship: A relationship that does not produce a straight line on a graph Output energy: Energy that comes out of a device Potential energy: Energy that is stored Sound: Energy that can be heard Speed: The rate at which an object changes position Thermal energy: A form of energy that can be transferred as heat Total energy: The sum of all forms of energy in a situation Useful energy: Output energy that is put to the intended use Waste energy: Output energy that is not put to the intended use Heat Heat and Thermal energy: We usually think of heat as something that warm objects have and cold objects lack. But when we're talking about heat, we're usually talking about thermal energy. Heat and thermal energy are not quite the same thing: - Thermal energy is the energy in an object that determines its temperature. - Heat is the transfer of thermal energy from a hotter object to a colder one. For example, when you hold a mug of hot chocolate on a cold day, you are feeling its heat. Thermal energy is transferred from the mug to your hands because your hands have a lower temperature than the mug. The amount of thermal energy in an object depends on its temperature. But it also depends on the object's size. The hotter and bigger an object is, the more thermal energy it has. However, the only thing that matters for the transfer of thermal energy is a difference in temperature. Thermal energy transfer can continue until both objects reach the same temperature. At that point, the transfer of thermal energy stops. Heat and the kinetic energy of particles: All matter is made up of particles – atoms, molecules or ions – that are far too small to see. The particles are always moving, and so they have kinetic energy, the energy of movement. The particles in solids, liquids and gases have different amounts of kinetic energy. In gases, particles move freely at high speeds and have a lot of kinetic energy. In solids, the particles have less kinetic energy and simply vibrate in fixed positions. Thermal energy is determined by the motion of these particles. Think about two steel blocks with the same mass but different temperatures. The block with the higher temperature has more thermal energy because its particles have more kinetic energy. The block with the lower temperature has less thermal energy because its particles have less kinetic energy. All substances have some thermal energy – even very cold ones – because particles are always moving to some degree. Note: Particles with low thermal energy are vibrating with each other, like the diagram of the solid shown above. Particles with high thermal energy are spread apart, like gas. Conduction: There are three types of ways heat can be transferred: Thermal energy transfer occurs in many different ways when you cook a pizza in a wood-fired oven. One way it occurs is when thermal energy moves from the hot bricks on the floor of the oven to the dough. The dough absorbs the thermal energy and begins to cook. Similarly, when you hold a slice of hot pizza in your hand, thermal energy is transferred from the pizza to your skin. Thermal energy is always transferred from areas of higher temperature to areas of lower temperature. The examples above involve thermal energy being transferred through direct contact between two objects. This type of heat is called conduction. When two objects are touching, the hot object will transfer thermal energy to the colder object through the process of conduction. Particles in the hotter object move more and have more kinetic energy. This means that the object has more thermal energy. As particles in the hot object collide with particles in the cooler object, they pass on some of their kinetic energy. This causes the cooler object to heat up. Thermal energy continues to be transferred until both objects are at the same temperature. Example → Key Question: One end of a long metal rod is heated by a fire. Explain why the other end of the rod will soon start to feel hot. When the hot moving/vibrating particles of the fire, which has more kinetic energy than the rod, bumps into the particles of the cold metal rod, through conduction, the particles rub against each other, creating thermal energy. Conductors and insulators: Different materials conduct thermal energy differently. Any material that allows thermal energy to flow through it easily is called a good conductor. All metals are good conductors, although some metals are better than others. We use metals to make pots and pans because they conduct thermal energy to the food quickly. A material that doesn't allow thermal energy to flow through it easily is called an insulator. Plastics, air, wood and cloth are examples of good insulators. What makes a good conductor? As we have seen, some solids are much better conductors of thermal energy than others. For example, metals are very good conductors, while plastics are good insulators. But in general, solids tend to be better conductors than liquids and gases. This is because of the way their particles are arranged. Conduction requires particles to collide with each other so that kinetic energy is passed from one particle to another. The transfer of kinetic energy between particles explains the transfer of thermal energy through a substance. The following diagram explains why thermal energy transfer is usually better in solids compared to liquids and gases. Convection: Convection is the transfer of thermal energy through fluids (substances that can flow) from a warmer area to a cooler area; one area of fluid to another due to the differences in density. You may have heard the saying “hot air rises”. You can see this action when a hot air balloon lifts off the ground. As the air inside the balloon heats up, it expands, and becomes less dense than the cooler air outside. The difference in density causes the balloon to rise. During the flight, the air inside the balloon cools and contracts. This makes the air denser, causing the balloon to slowly fall. These upward and downward movements of air transfer heat and are examples of convection. Convection also occurs in a lava lamp. In this case it's not hot air rising but a liquid in oil. When the liquid is heated by the lamp, it becomes less dense and rises through the oil. As it cools, it becomes denser again and slowly falls. Differences in the density of fluids explains why they rise or fall. For example, oil floats on water because the water is more dense. Gravity pulls down on the water more than the oil, causing it to sink. This pushes the oil up so that it floats on the water. When fluids are heated or cooled, their density changes. When fluids are heated, their particles move more quickly and gain kinetic energy. As the particles move about more, they spread further apart. The fluid expands and becomes less dense. When fluids are cooled, their particles move more slowly and lose kinetic energy. As the particles move less, they are closer together. The fluid contracts and becomes denser. Convection is the transfer of thermal energy from one area of a fluid to another because of differences in density. It can, therefore, be explained by the movement and kinetic energy of the particles that make up the fluid. Convection currents: When you heat water on a stove, the water is heated unevenly. The stove transfers thermal energy to the water at the bottom of the pot. The hot water is less dense than the cooler water above it. It rises to the top of the pot and loses thermal energy to the surroundings. As it cools, it becomes denser and sinks to the bottom of the pot, where it can be heated again. Circular movements of a fluid that are caused by temperature differences are called convection currents. The mixing produced by convection currents helps to spread thermal energy throughout the fluid. Radiation: The Sun's rays heat the Earth. You can feel this heat warming up your skin when you sit outside on a sunny day. The space between the Sun and Earth is a vacuum and contains practically no matter. This means that thermal energy can't be transferred by conduction or direct contact. It also can't be transferred by convection or the movement of fluids. The thermal energy originating from the Sun does not need particles at all. It travels in waves that move at the speed of light – around 300,000 km per second! This type of heat, involving waves, is called radiation. Radiant thermal energy is similar to visible light because they are both examples of electromagnetic waves. But most radiant thermal energy is invisible because it has longer waves than red light. For this reason, it is called infrared radiation. All objects radiate thermal energy. We can't see this thermal energy, but we can often feel it. The hotter something is, the more thermal energy it radiates. Reflection, absorption and transmission: Like light, infrared radiation travels in straight lines. When the waves hit a surface, they can either: ★ Bounce off the object – Reflection ★ Be soaked up by the object – Absorption ★ Pass through the object – Transmission Whether an object reflects, absorbs or transmits radiant thermal energy depends on the type of material and its colour. A black car heats up more quickly in the sunshine than a white car. This is because dark-coloured objects are good absorbers of radiation. In contrast, light-coloured objects tend to reflect radiation. Shiny metal surfaces are very good at reflecting radiation. However, radiation passes straight through clear materials, such as glass. Example of All three → Conduction, Convection & Radiation Glossary: Absorption: The process in which radiation is soaked up by an object Conduction: The transfer of thermal energy by direct contact Conductor: A material that conducts thermal energy well Convection: The transfer of thermal energy by the flow of a fluid Convection current: The circular movement of a fluid caused by heating Fluid: Any substance that can flow Heat: The transfer of thermal energy from a hotter object to a colder one Infrared radiation: Electromagnetic waves that can't be seen but can be felt as heat Insulator: A material that conducts thermal energy poorly Kinetic energy: Energy a moving object has because of its motion Radiation: The transfer of thermal energy by electromagnetic waves Reflection: The process in which radiation bounces off an object Thermal energy: The energy in an object that determines its temperature Transmission: The process in which radiation passes through an object Waves Sound: A wave is a repeated motion that transfers energy. In the case of water waves, the particles move up and down as the wave moves horizontally.Sound waves are vibrations in molecules that transfer energy but NOT matter therefore they have to travel through a medium. They transfer energy but not matter. There are 2 types of waves: Transversal Waves: - These waves move in an ‘up and down’ direction (perpendicular) going forward. Transverse Waves have low frequency. Light waves are transverse waves. Longitudinal Waves: - These waves move more in a back and forth direction going forwards. Longitudinal waves have high frequency. Sound waves are longitudinal waves Transverse Waves Image: Longitudinal Waves Image Compression and Rarefaction: When a sound wave passes through, the air in some areas compresses, meaning the molecules there become more densely packed, and air in other areas rarefies, meaning the molecules become more spaced apart. As the sound travels through the space the molecules vibrate so that the areas of compression and rarefaction shift, even though the molecules themselves stay roughly in the same place. You can see this in the diagrams below showing a sound wave as it moves across a room. Two specific molecules have been marked to show how, although they shift about, they do not move along with the wave. Diagram of Compression and Rarefaction: Amplitude, Wavelength and Frequency: Amplitude: the height of a wave measured from the middle Wavelength: the number of waves that go by in a second Frequency: the distance between two wave crests The trough is the lowest point whereas the crest is the highest point of a wave. Amplitude is related to how loud something is. High amplitude means a noise is very loud and low amplitude means it is not very loud or it is quiet. ○ Less Compression: Low Amplitude More Compressions: High Amplitude Wavelength and frequency are related to the pitch of the sound, or the note, as in music. - Sound waves with shorter wavelength and higher frequencies we hear as higher notes - - Sound waves with longer wavelengths and lower frequencies we hear as lower notes. The Speed Of Sound: For sound, the lowered “Tension” setting represents a medium where the molecules are less densely packed, with looser bonds between them. -In materials where the molecules or atoms are closely packed, sound travels quickly -In materials where the molecules or atoms are only in contact with each other loosely and intermittently, sound travels more slowly. Due to how densely compacted the molecules are, the slower sound moves in it. For example steel is a solid so its molecules are more densely packed cousin sound to move faster than water or air. Water has more tightly packed molecules so sound travels faster in water than air. Light: Light Waves: Light is a type of energy. Unlike sound, light can travel through space even where there is no matter. This is how sunlight travels from the Sun to reach Earth. It takes about 8 minutes for light to make this journey. The speed of light is incredibly fast – nearly 300,000 kilometres per second. Light usually travels in transverse waves. - The period of a wave is how long it takes to go through its full motion once. - - The frequency is how many waves go by in a second - - The wavelength is the distance between one crest (top of a wave) to the next or the trough (bottom of the wave) to the next. The Visual Spectrum of Light: The visual spectrum of light is the spectrum of colours that we can see. This includes the colours: Or it can be remembered by the abbreviation ROYGBIV. The lower end of the spectrum like the colours red and orange have low frequency as well as a longer wavelength than colours on the higher end of the spectrum like indigo and violet which have a higher frequency with a shorter wavelength. White light has all of these colours inside of it and when you see. An object that appears to have colour is really just the light that is hitting that object, all the colours on the spectrum are being absorbed by the object and the colour it seems to be is being reflected. For example an apple would absorb every other colour on the spectrum and only reflect red making it appear red to the eye. Black and white objects are special though as black absorbs all light causing it to heat up more than white objects and white reflects all colours so it is much cooler when exposed to light or heat. The Interaction Of Light With Objects: Light interacts with different objects and surfaces differently. Notably in 3 major ways being reflection, absorption and transmission. Reflection: When light hits a surface it bounces off Absorption: Light energy is transferred into heat energy into the object instead Transmission: Light passes through an object Light interacts differently with different objects as well. Objects that are transparent (completely see through) light transmisses meaning transmission. With translucent objects (slightly see through) light sometimes gets absorbed and sometimes transmisses and sometimes both but with opaque objects (can not be seen through at all) then light reflects and/ or absorbs. The Electromagnetic Spectrum: Short Wavelength = Low energy Long Wavelength = High energy The visible light spectrum is not the only spectrum of energy. ;First there are the low energy and long wavelength waves like radio waves, microwaves and infrared rays. After them comes the visible light spectrum. After the visible light spectrum comes ultraviolet rays, x-rays and gamma rays. These are all very high frequency and short wavelength types of rays and waves. Diagram: Reflection: Light always travels through air at the same speed and in a straight line. When light hits an object, some of it bounces or reflects off the surface. The type of surface determines how the light reflects: -Uneven or rough surfaces reflect light rays in different directions. This scattering of light is called diffuse reflection. -In contrast, smooth, shiny surfaces reflect light rays in a regular pattern. This allows us to see a clear image reflected back at us and is called regular reflection. Mirrors are a great example of this. The law of reflection: The way a light ray reflects off a surface follows a simple pattern. The incoming ray is called the incident ray. To work out the direction of the reflected ray, we can think of a line at right angles to the surface. This line is called the normal. As shown in the diagram below: - The angle between the incident ray and the normal is called the angle of incidence. - The angle between the reflected ray and the normal is called the angle of reflection. Diagram: Law of reflection and reflection off of a smooth surface Reflection of Rough Surface Reflection of Smooth Surface Refraction: Light always travels at the same speed and in a straight line unless it encounters an object. When light changes mediums like from liquid to gas then it slows down slightly and bends. This bending of light as it passes from one medium to another is called refraction. When the light refracts so do the colours and the colour that bends the most in refraction is violet as it is the highest frequency as shown in the picture below. Diagrams: Bending of colours when refracting: Diagram Explaining Refraction: Lenses: A lens is a curved piece of transparent glass or plastic that refracts light. Since a lens is curved on at least one side, light rays striking different parts of its curved surface change direction by different amounts. Depending on the shape of the lens, the light rays either: - Get further apart or diverge →e lens - Get closer together or converge → convex lens Concave lenses: A lens that is curved inwards and is thinner in the middle is called a concave lens. Concave lenses cause parallel rays of light to diverge, or spread out. Concave lenses in glasses that are used for people who can’t see objects far away and in peepholes in hotels. Note: The image formed by a concave lens is always smaller than the object it represents. Convex Lens: A lens that is curved outwards and that is thicker in the middle is a convex lens. Convex lenses cause parallel light rays to converge, or get closer.Convex lenses can produce images that are either larger or smaller than the objects they represent: - Larger (magnified) images are formed when the object is located between the lens and the focal point. - Smaller images are formed when the object is located more than two focal lengths from the lens. The object will appear upside down. Magnifying glasses are examples of convex lenses that are used to produce larger images. To do this, they need to be held quite close to the objects you want to magnify. The point where parallel rays converge is called the focal point. Just as for concave lenses, the distance between the focal point and the centre of the lens is the focal length Concave Lens when light passes through Convex Lens when light passes through Glossary: Amplitude: The distance between the midline of the wave and the top or bottom. The amplitude of a sound wave relates to the amount of energy it transfers. Compression: Part of a sound wave where particles are closer together. On a wave graph, a compression is represented by a high point, or crest. Decibel: A unit used to measure loudness. A normal conversation has a loudness of about 60 dB. A jet plane taking off has a loudness of about 140 dB. Frequency: The number of waves that go by in one second. The higher the frequency of a sound wave, the shorter its wavelength. Hearing Range: The range of frequencies that can be heard by a human or animal Humans can hear sounds between about 20 Hz and 20,000 Hz. Other animals have different hearing ranges. Hertz: The standard unit of frequency. Elephants communicate using very low frequencies that we can't hear. High Pitched: The quality of sounds produced by waves with high frequency. A small bell vibrates very quickly, producing a high-pitched note. Longitudinal waves: A wave in which particles move back and forth in the wave direction. Sound waves are longitudinal because the particles move back and forth in the same direction as the wave. Loud: The quality of sounds produced by waves with high amplitude. Loud sounds involve sound waves with more energy that disturb the particles more. Loudness: A quality of sound that depends on the amplitude of the sound wave. The greater the amplitude of a sound wave, the more energy it has and the louder it sounds. Low-Pitched: The quality of sounds produced by waves with low frequency. A large drum vibrates slowly, producing a deep, booming sound. Medium: A substance that a wave travels through. Sound waves can only travel through a medium, such as air, water or steel. Pitch: A quality of sound that depends on the frequency of the sound wave. The higher the frequency of a sound wave, the higher it sounds. Quiet: The quality of sounds produced by waves with low amplitude. Quiet sounds involve sound waves with less energy that disturb the particles less. Rarefaction: Part of a sound wave where particles are further apart. On a wave graph, a rarefaction is represented by a low point, or trough. Sound: A type of energy transmitted by vibrating particles. Sound can travel through solids, liquids and gases. It cannot travel through a vacuum, such as outer space. Soundwave: A vibration of particles that transfers energy. Sound waves are produced by vibrating objects, such as a ringing bell or the vocal cords in someone's throat. Transverse wave: A wave in which particles move at right angles to the wave direction. Ocean waves are transverse because the particles move up and down as the wave moves horizontally. Wave: A repeated motion that transfers energy. Waves can take many different forms, including sound, light, earthquakes and ocean waves. Wavelength: The distance between one crest of a wave and the next crest. The longer the wavelength of a sound wave, the lower its frequency. Absorption: Magnifying glasses are examples of convex lenses that are used to produce larger images. To do this, they need to be held quite close to the objects you want to magnify. Colour: A property of visible light that depends on its frequency. The lowest frequency of light that we can see is red, and highest is purple. Concave Lens: A lens that is curved inwards and is thinner in the middle. Concave lenses cause light rays to diverge and produce smaller images. Converge: To get closer together. Convex lenses cause parallel light rays to converge. Convex Lens: A lens that is curved outwards and is thicker in the middle. Convex lenses cause light rays to converge and can produce either bigger or smaller images. Diverge: To get further apart. Concave lenses cause parallel light rays to diverge. Focal Length: The distance between the centre of a lens and its focal point. The focal length depends on how strongly the lens refracts light. Focal Point: A place where light rays either converge to or diverge from. The focal point is located behind a concave lens and in front of a convex lens. Frequency: The number of waves that go by in one second. Frequency is measured in waves per second. Higher frequency waves have shorter wavelengths. Lens: A curved piece of transparent glass or plastic that refracts light. Lenses have many useful applications, including glasses, cameras, microscopes and telescopes. Light: A type of energy that travels in electromagnetic waves. Light energy allows us to see the world around us. It also provides plants with energy needed to make food by photosynthesis. Magnification: A measure of a lens's ability to increase the size of an image.A magnifying glass with a magnification of 2x makes things appear two times larger than they really are. Opaque: Not allowing light to pass through. Because light is absorbed by opaque materials, we cannot see through them Period: The time it takes a wave to go through its full motion once.The faster a wave moves back and forth, the shorter its period. Periodic Motion: Movement that is repeated at regular intervals.A cork bobbing up and down on ocean waves is an example of periodic motion. Prism: A transparent object with flat surfaces, which refract light. Prisms demonstrate that white light is a mixture of all colours, which are refracted by different amounts. Reflection: The bending of light as it bounces off a surface. White objects reflect all frequencies of light. Blue objects reflect mostly blue light. Refraction: The bending of light as it passes into a new material. The refraction of light by lenses has many useful applications, such as cameras, microscopes and telescopes. Translucent: Allowing only some light to pass through. Because only some light passes through translucent materials, objects appear blurred. Transmission: The passing of light through a material. A window is made of glass that transmits light, allowing us to see through it. Transparent: Allowing nearly all light to pass through. Because light passes through transparent materials, we can see through them clearly. Visible Spectrum: The range of light frequencies that we can see. The visible spectrum includes all the colours of the rainbow. Wave: A repeated motion that transfers energy. Unlike sound waves and ocean waves, light waves can travel through a vacuum. Wavelength: The distance between one crest of a wave and the next crest. Different colours of light have different wavelengths. Red light has the longest wavelength in the visible spectrum. Non-Contact Forces & Electricity Non-contact forces: There are many different types of non-contact forces, but the ones that’s going to be in the exam are going to be: -The Magnetic Force -The Electrostatic Force -The Gravitational Force But what are non-contact forces? Well they are forces that act on another object from a distance and don't have to touch it. Magnetic Force Magnets are very common and can be found everywhere from toys to refrigerator decorations but magnets can’t stick to everything. Magnets can only push and pull on things that are magnetic. The force produced by magnets pulling and pushing on objects is called the magnetic force Electrostatic Force: The electrostatic force is the force produced when charged objects push or pull on other objects. The electrostatic force between two objects is greater when they are more charged or closer to one another. Just like magnets, opposite charges attract and like charges repel each other Gravitational Force: Kind of obvious but the gravitational force is gravity which is a force that pushes things down, it’s the reason why balls come down when you throw them and why we aren’t floating off into space right now. Gravity works on objects from a distance and can only attract and never repel. Magnetic Fields: The area around a magnet is where the force from the magnet can be detected, this is called a magnetic field and a diagram is at the bottom of this heading All magnets have a magnetic field; we just can’t see them. Iron fillings can be used to see this field around the magnet Magnetic fields around magnets show us where the force from the magnet is the strongest or weakest. If you use the iron fillings technique then where the iron fillings are close together, the field is stronger and where they’re further apart, it’s weaker. DIAGRAM: This is what the magnetic fields of magnets that attract and repel look like: Electric Circuits: What is electric current?: Electric current is the flow of electrons through a circuit. Whether you realise it, you already know a lot about electric currents The measurement of current is Ampere (A) or amps for short. A current of 1 amps means that 6,241,000,000,000,000,000 electrons are passing through a point in the circuit every second. The higher the current, more energy is supplied. For example, increasing the current makes a light globe shine brighter. What is a circuit? A circuit is a pathway of electricity to flow through. For electrons to flow around they need an unbroken and smooth path. Circuits also have many components in them such as switches, batteries, light bulbs and more Every part of the circuit must allow electrons to flow through it. Materials with this property are called electrical conductors. Metals are used in circuits because they are good conductors How to draw a circuit: The different components of a circuit have different symbols that are shown in the diagram below: Ohm’s Law: What affects the flow of electricity?: The electric current in a wire is the movement of electrons. We can’t see this current. This makes it hard to understand exactly what’s going on. To help explain I’m going to use the example of a river. What speeds up current?: Like water in a river, electrons in a circuit need energy to move. The amount of energy given to electrons is called voltage and voltage is measured in volts (v) What slows down current?: The water in a river slows down as it runs into rocks and logs. The same thing happens with electrons. As they hit obstacles, they are slowed. This decreases the current speed. A material’s opposition to the flow of the electric current is called resistance which is measured in ohm’s, it’s symbol is the omega symbol Many different parts of a circuit can add resistance. These include light bulbs, speakers and motors. There are also special components designed to reduce the current. These are called resistors. Most circuits have more than one component that adds resistance. The total resistance is equal to the sum of the resistances of all components. How can you calculate current?: The relationship between current, voltage and resistance is called Ohm’s law. So far, I’ve described this relationship using words. But the relationship can also be described mathematically. Ohm’s Law can be written as an equation like this: V = I x R - V = Voltage (V) - I = Current (A) - R = Resistance (Ω) Just like all mathematical equations, Ohm’s law can be switched to find different values. We call this transposing the equation. The unknown variable should be by itself on the left hand side. This is called the subject of the equation. The diagrams below are a quick way to find the right equation, depending on what you need to calculate: Series And Parallel Circuits: Not all circuits are the same. Instad, they fall into two main types. Most circuits that were covered on stile have only one single path for electrons to flow through. The current must flow through all of the components in the circuit. This is called a series circuit. But in some circuits, there is more than one pathway electrons can take. In these circuits, only part of the current flows through any branch. This is called a parallel circuit. Positives and Negatives of Parallel Circuits: Positive: - More than one path for electrons to flow - If a main switch does not malfunction then the circuit keeps running - Each light bulb/ appliance gets full voltage rather than half such as in series circuits - If one appliance is switched on, the others are not affected - Lights will be brighter as a result of the full power distribution of parallel circuits Negatives: - Much more complex and more wires than a simple series circuit - All components have the same voltage as the supply, so it may be harder to control if the components need to have different voltages Positives and Negatives of Series Circuits: Positives: - All the components can be controlled by a single switch - Fewer wires are needed - Less complex Negatives: - Components can’t be controlled separately - The appliances don’t get full power voltage rather only a fraction of it Glossary: Ampere:The unit of measurement for electric current Attracted: When one object is pulled toward another object Circuit: A pathway for electricity to flow through. A circuit must contain an unbroken path that electrons can flow through Constraints: Factors that limit possible solutions to a problem Criteria:Standards engineers create to judge solutions Electric Current: The flow of electrons through a circuit Electromagnet: A magnet made by running electric current through a wire Electromagnetic Force: The force produced by a current-carrying wire Electrostatic Force: When a charged object pushes or pulls on another object Magnetic Field: The area around a magnet where magnetic forces can be seen Magnetic Force: The force produced when magnets push or pull other objects Magnetised:An object that has magnetic properties Non-Contact Forces: Forces that act on an object at a distance such as the electrostatic force, gravitational force and magnetic force North Pole: The end of a magnet that will attract a south pole Ohm’s Law: The relationship between current, voltage and resistance Parallel Circuit: A circuit with more than one branch current can flow through Permanent Magnet: An object that stays magnetised for a long time Pole: The regions at the end of a magnet Repelled:When one object is pushed away from another object Resistance: A material's opposition to the flow of electric current Resistor: Components in a circuit designed to reduce the current Series Circuit: A circuit with only one path for electrons to flow through South Pole: The end of a magnet that will attract a north pole Testable Question: A question with a measurable outcome Voltage: The amount of energy given to electrons by a power source Atoms The Structure of Atoms: -An atom is made up of 3 types of subatomic particles (subatomic meaning they are smaller than an atom). These are as follows: 1. It can also be found in the nucleus 2. Electron: An electron has a mass of 1/1840 but you can write it is 1/2000, it has an overall negative charge and can be found around the nucleus in the outer shells/ orbitals 3. Proton: A proton has a mass of 1 and it has a positive charge, it can be found in the nucleus Neutron: A neutron has a mass of 1 like the proton and it has a neutral charge , -An atom has a nucleus which is like its core, this is where most of the weight of the atom can be found and around it are orbitals which hold electrons. Note: In the picture above you can see there are small circles where the electrons can be found in, those are called the orbitals, in each orbital there can only be specific number of electrons and this will be covered later on under the “Ions” heading Brownian Motion: Some background information that led to the discovery of brownian motion, an english scientist named Robert Brown was so bored the idiot was studying pollen under a microscope and saw that the pollen grains were floating in the water and moving almost all the time. Now what Brownian motion really is: It is the random and almost continuous motion of microscopic particles (particles that can only be seen under a microscope) in water. In 1905 Einstein said that Brownian motion happens due to collisions between the grains of pollen and invisible water molecules. A water molecule is 2 hydrogen atoms and one oxygen atom. Atoms and Neutrons: All atoms of the same element have the same number of protons. The number of protons an element has is called its atomic number. For example the atomic number of the element neon is 10, that means that it has 10 protons in it and is the 10th number on the periodic table. But if you add another proton into the element of neon then it becomes a completely different element and doesn’t remain as neon. When writing an atom you write the atomic number at the top. Neutral Atoms: Keep in mind that atoms have 3 types of subatomic particles being protons, neutrons and electrons. A different mixture of these creates an atom with a different overall electrical charge. For example if there is an equal number of protons and electrons that means that it is considered a neutral atom. But if an atom has more protons than electrons and neutrons then its overall electrical charge would be positive. Note: Neutrons don’t count to the overall charge of an atom as they have no charge so make no difference Ions: In an atom well know that in the nucleus is where the protons and neutrons are located and that the electrons are on the outsides of the nucleus in the orbitals and therefore they can be removed from the atomic structure much easier meaning that electrons can be transferred from one atom to another one. When an atom gives away or takes an electron, the balance between positive and negative charges isn’t the same anymore this causes a particle to form that either has a positive or negative charge being an ion. If it is a positively charged ion it is called a cation and an anion is a negatively charged ion. Each element has its own symbol on the periodic table for example oxygen is O and sodium is Na or gold is Au. You can find out the charge of an ion by looking at its symbol, if it is a negative 2- oxygen ion the symbol will have a negative sign and will look like this: “ O ” this means that it has a negative charge of 2. A cation(positive ion) with a charge of 2 would look the same but would have a “+” symbol. Why do ions do this? Ion wants what is called a stable electron configuration, this means that every one of their shells is filled, they can do this by giving away enough electrons to lose a shell or take enough electrons to gain finish off a shell. The rule of thumb is that if an atom has less than 4 atoms left in one shell it will give away its electrons but if it has more than 4 it will take electrons from other atoms that are giving away their electrons. Now each shell of an atom can only have a certain amount of electrons, in the first shell, the atom can only have 2 electrons, but for shells 2,3 and 4 then its max electrons in those shells can be 8. Mass Number: Neutrons have no charge so they make no difference to the overall charge like said before but they have the same mass as a proton being a mass of 1 so they make a very big difference to the mass number of an atom. Electrons are the lightest if you look at mass out of the 3 subatomic particles so they can basically be ignored when looking at the mass but not the overall charge. Now getting to the point, the mass number of an atom is the number of protons and neutrons in the nucleus. The equation to find the mass number is: “number of protons + number of neutrons = mass number'' Isotopes: This is the bit that everyone struggles with. Basically an isotope is when the element has the same number of protons and different number of neutrons, think of it like remixes of songs, they have slight differences. Now you write the number of protons in the symbol when it is an isotope. For example if you had an isotope of carbon that had 12 neutrons it would be called Carbon-12 and as a proper symbol you would write the mass number (proton and neutrons) of the atom at the bottom and don’t write the isotope number. For example carbon-12 would be written as: From this image you can also infer that there are 6 neutrons and protons as if there is 6 as the atomic number (one at the bottom) that means there must be 6 neutrons since 12-6 is 6. Note: If there is just one number at the top of the symbol, that means that the number at the top is the atomic number. Radioactive Decay: There are 3 types of radioactive decay being, alpha, gamma and beta decay. Alpha Decay: This decay occurs when the proton to neutron ratio is too low. It's when an unstable atom turns into another element by shooting out a particle with 2 protons and 2 neutrons. The structure of this particle is the exact same structure of a helium atom but it isn’t a helium it is called an alpha particle, it is only written as a helium particle for simplicity in the formula for alpha decay. There is also a formula for alpha decay, when describing an alpha decay, the atomic number is reduced by 2 and the mass number is reduced by 4. For example in this case you would take 2 from the mass number making it 235 and you would take away 4 from the atomic number and look for the new element it creates and write that. All together the new atomic number makes it the atom Uranium with an atomic number of 92 so you write that at the bottom and you take away 4 from the mass number which is 235 so you write that at the top. Then you write the symbol for alpha at the end of the equation to show that it is an alpha decay. Beta Decay: This decay occurs when there are too many protons or neutrons in the nucleus of an atom. In this decay one of the protons or neutrons in the nucleus is transformed into another proton or neutron depending on which one broke off. This means there is an increase in the atomic number by 1 and the mass number stays the same. The particle that is formed has the same structure as an electron but is written with the beta symbol which looks like a b with the stick slightly extending past the loop of the b. For example in this case you would add one to the mass number or the number at the bottom turning it into another element being Nitrogen in this case and the number on top or the mass number and to finish it off you would write the symbol of beta to symbolize that it is a beta decay. Gamma Decay: This type of decay occurs when a nucleus has too much energy and is not stable. A nucleus turns from a high energy state to a low energy state by emitting photons (electromagnetic radiation). In this decay the mass and atomic number stays the same. You don’t have to know the formula for gamma decay. Glossary: Atom: The smallest particle of an element. Atomic number: Number of protons in an atom Charge: An electrical property of matter Electron: A subatomic particle that has a negative charge and a mass of 1/1840 but you can write it as 1/2000 Element: A substance made up of only one type of atom Ion: An ion or particle that has gained or lost an electron Isotope: A variation of an atom that has a different number of neutrons than protons Mass number: The atomic and mass number combined Molecule:A group of atoms bonded together Negative ion (anion): An ion that has an overall negative charge Net charge: The overall electrical charge of an atom Neutral particle: An atom that has the same number of protons and electrons Neutron: A subatomic particle that has no charge Nucleus: The centre of an atom that contains most of the mass of the atom and all of the protons and neutrons Positive ion (cation): An ion that has an overall positive charge you can remember this by thinking that cats make you happy/ positive so cations have a positive charge Proton: A subatomic particle that has a positive charge Radiation: The energy of particles that are released in radioactive decay Radioactive decay: The process of unstable atoms releasing radiation Stable isotope: A variation of an atom with a different amount of neutrons than protons that is not likely to break apart Subatomic Particle: A particle that is smaller than an atom, There are 3 being protons, neutrons and electrons Unstable Isotope:A variation of an atom with a different amount of neutrons than protons that is likely to break apart Chemical Reactions Physical and Chemical Changes: Physical Change: In a physical change no new substances form. It involves a change of physical properties such as. In a physical change something like the position, shape size or state of matter changes such as ice going to water. Chemical Change: In a chemical change, new substances are formed. Some typical signs of a chemical change include a release of light or sound, a formation of a new gas, a change in color, the disappearance of a solid, the formation of a new solid or a change in temperature. A chemical change could be something like iron rusting or wood burning Reactants and Products: A chemical reaction is the transformation of one or more substances into new substances. These substances may be either elements or compounds. - Elements include any of the basic substances on the periodic table, such as oxygen or iron. They are made up of one type of atom. - Compounds are made up of two or more different types of atoms bonded together, such as carbon dioxide and sodium chloride. The chemical formula of a compound shows the relative number of atoms of each element. - The roles of the substances in a chemical reaction are identified by special terms: - The substances that react with each other are called reactants. - The new substances formed by a reaction are called products Chemical Equations: Word equations: Word equations are literally what they sound like, it is an equation that has the names of the elements and substances in it. For example: sodium+oxygen→ sodium oxide is a word equation. There Are a few simple rules for writing word equations: - Draw an arrow to represent the reaction - Write the names of the reactants on the left side of the arrow - Write the names of the products on the right side of the arrow - Seperate different reactants or different products by adding a plus sign - Keep the equation on a single line Symbol Equations: Symbol equations are the same as a word equation but you use the symbols in the equation rather than the entire word. For example a symbol equation would be Na+O2→NaO2 Balancing chemical equations and The law of conservation of matter: The Law of Conservation of Matter: The law of conservation of matter states that matter can not be created or destroyed. This means that in chemical reactions the number of each atom of each element stays the same. When the chemical equation does not have the same amount of atoms on the left side and the Right side it means the equation is unbalanced and needs to be balanced - An unbalanced equation is where there are unequal numbers of atoms on an element on either side. - A balanced equation is when there are equal numbers of atoms on each side. For example an unbalanced chemical reaction would look like Fe2O3 + Al → Fe + Al2O3 This is unbalanced as on the left side there are 2 atoms of iron or Fe and on the right side there is only one atom and on the left side there is only 1 aluminium atom but on the right side there is 2. This means to balance it out you need to add a 2 to the aluminium on the left side and a 2 to the iron or Fe on the right side. This would mean that a balanced equation would look like this: Fe2O3 + 2Al → 2Fe + Al2O3 Glossary: Alkali Metal: Highly reactive metals that are in group 1 in the periodic table. They explode in water. An example would be sodium Aqueous solution: A mixture in which something is dissolved in water Balanced: Has the same amount of atoms on both sides of a chemical equation Chemical bond: A strong force that holds atoms or lattice together Chemical change: A change where the substance is chemically altered. Some signs of this are the creation of a new substance, change in colour or temperature. Full list is under the chemical and physical change heading. Chemical equation: This is an equation whether it be in words or picture form how elements are rearranged in a chemical reaction Chemical formula: A symbol that shows the composition of a molecule. Chemical reaction: The rearrangement of atoms to form one or more new substances Chemical symbol: One of 2 letters used to represent an element Coefficient: A number placed before a chemical symbol in a chemical equation to make sure that the equation is balanced Combustion: A chemical reaction in which a fuel reacts with oxygen and releases heat. Compound: A substance with 2 or more elements Dihydrogen Monoxide: The chemical name for water (H2O), because a water molecule contains two (di-) hydrogen atoms bonded to one (mon-) oxygen atom Electrode: A piece of metal that is used to pass an electric current from a battery to another living thing or a material Element: A substance that has only one type of atom such as oxygen or gold Hypothesis: An educated guess that you make at the beginning of an experiment and at the start of a scientific report about how you think the experiment will turn out Lattice: A repeating pattern of atoms in a metal or a repeated pattern of ions in an ionic compound Law of conservation of matter: This law states that matter can not be created or destroyed, this is why both sides of a chemical equation must have equal amounts of atoms on each side Millisecond (ms): A measurement of time that is smaller than a second Mixture: A combination of 2 or more substances Molecule: A group of atoms bonded together Periodic table: A table where all the known elements are arranged in groups Physical change: A change where the chemical structure of something is not changed such as ice melting. You can tell if it is a physical change if it is reversible easily, for example you can refreeze water to make it back into ice. Pollutant: A substance released into the atmosphere that causes harm to humans or wildlife Product: A substance formed by a chemical reaction. In a chemical equation the products are placed on the right hand side of the equation. Reactant: What substances react to create the product. In a chemical equation these are placed on the left side of the equation and have a “+” symbol to separate the reactants. Reactive: Takes part in chemical reactions often Solution: A type of mixture that occurs when one substance dissolves in another State symbol: A symbol used to represent what state of matter something belongs to for example (s) means that the substance is a solid, (l) is liquid and (g) is gas Structural equation: A type of chemical equation that shows how the atoms are rearranged Subscript: A small number used within a chemical formula to indicate how many atoms of an element are present; for example, in H2O there are two hydrogen atoms but only one oxygen atom (the 1 is not written); not to be confused with a coefficient Symbol Equation: A type of chemical equation where there are equal numbers of atoms on either side of the equation Unbalanced: This means that a chemical equation does not have the same amount of atoms on one side and the other Word equation: A type of chemical equation that uses names to represent the substances involved in a reaction Acids and Bases Acids: Acids are substances that all share these properties: - They have a sour taste - They react with metals - They can be and usually are corrosive - They are solutions of a compound dissolved in water - An example of an acid would be stomach acid or acid found in citrus fruits like oranges or lemons Bases: Bases are substances that all share these properties: - They can be solid or liquid - Some solid bases can be dissolved in water. A base that is soluble in water is called alkali - They have a soapy, slippery type of feel - They have a bitter taste - They are corrosive. Strong bases often burn the skin and this is called being caustic. - An example of a base would be sodium bicarbonate which is baking soda Neutral Substances: A neutral substance is a substance that is not acidic or basic, it isn't a base or an acid. In fact when acids and bases mix they make a neutral substance which will be important later on. Neutral substances share some of the properties stated below: - They are NOT corrosive - they are harmless if you touch them - They may have either a sweet or salty taste or might not taste like anything. - An example of a neutral substance would be purified or distilled water Measuring Acidity: We all know that ions are atoms or molecules that have an electrical charge whether that be positive or negative. Whether a substance is a base or an acid depends on the type of ion it releases when it dissolves in a solution. - Acids release more hydrogen ions - Bases release more hydroxide ions A hydrogen ion is simply a hydrogen atom that has lost an electron, giving it a positive charge. A hydroxide ion is made up of an oxygen atom bonded to a hydrogen atom. It has an overall negative charge Diagram of hydrogen and hydroxide ions: Now acidity can also be measured on a scale that measures pH which ranges from 0-14, the closer if a number ranges from 0-7 it means that it has more hydrogen ions making it more acidic but if the substance ranges from 7-14 it has more hydroxide ions meaning it is more basic. If a substance has a pH level of exactly 7 or a few decimal points off 7 it is considered neutral or somewhat neutral. For example stomach acid has a pH level of 2, that makes it acidic. Blood has a pH level of 7.4 so it can be considered somewhat neutral or even slightly basic as it leans more towards the basic side of the spectrum. Acid Base Reactions/neutralization: To stop the properties of acids from having an effect, a base can be added to it and vice versa. For example, indigestion (caused by stomach acid) can be relieved by swallowing an antacid tablet which contains a weak base. Similarly, to stop a base from having an effect, an acid can be added to it. For example, the effect of a jellyfish sting can be neutralized by gently rinsing it with a weak acid such as vinegar. Now this is where neutralization comes in. Neutralization is a chemical reaction where an acid and a base react to produce water and salt, the word equation or it would be: Acid+base→Water+salt Hydrochloric acid + Sodium Hydroxide → Sodium chloride + Water During neutralization, the other atoms in the acid and base form a salt. For example, in the neutralization reaction between hydrochloric acid (HCI) and sodium hydroxide (NaOH), water is created leaving chloride (negative ion) and sodium ions (positive ion). The chloride and sodium can form sodium chloride (naCI), which is most commonly known as table salt. Like water, it is a neutral substance. This reaction is shown in this diagram: Carbon Dioxide Bubbles: All neutralisation reactions produce salt and water. However one type of neutralisation also produces bubbles of carbon dioxide or CO2. This happens when the base is a carbonate such as calcium carbonate (CaCO3)or sodium bicarbonate (NaHCO3) The reaction fizzes as bubbles of carbon dioxide are given off The reaction between an acid and a carbonate can be expressed as a word equation: Acid + carbonate → Water + salt + carbon dioxide Ocean Acidification: A decrease in a substance’s pH is called acidification. This process is currently taking place in our oceans. When carbon dioxide and water react, they produce carbonic acid. This is shown in the diagram below. In a water solution, carbonic acid splits to produce a bicarbonate ion and release a hydrogen ion Why is this all important? It’s important because when the concentration of hydrogen ions in the ocean increases, it becomes more acidic. Levels of Carbon Dioxide and Ocean Acidity: The following table shows the concentration of carbon dioxide in the atmosphere since 1875. The concentration is measured by the number of carbon dioxide molecules found in one million molecules of gas in the air. The units used to describe this value are called parts per million or ppm as an abbreviation Now the overall trend is that the CO2 (ppm) is going up every year meaning that ocean acidification is getting worse every year. The 4 Reactions There are 4 major reactions that you need to know. These 4 reaction are: 1. Synthesis 2. Decomposition 3. Combustion 4. Replacement Synthesis: Synthesis is a reaction in science where multiple reactants all combine to form one single product. An example of this could be oxygen and carbon combining to form carbon dioxide. The chemical equation for this would be: C+O2→CO2 Image: Decomposition: Decomposition is a reaction in science where a compound breaks down into two or more smaller, much simpler substances, it is the exact opposite of synthesis. An example of this would be Carbon monoxide breaking down into carbon and oxygen atoms. The chemical equation for this would be: CO→C+O Image: Combustion: Combustion is a reaction in science where a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O2 as one of the reactants and a combustion reaction also always produces CO2 and H2O. An example of this would be Methane gas and oxygen turning into carbon dioxide and water. The chemical equation for this would be: CH4+O2→CO2+H2O0 Image:(the only one found) Replacement: A chemical reaction where one element replaces another one in a compound. There is also double replacement which is when metals in 2 ionic compounds exchange partners. (no example found.) Glossary: Acid: A substance with a pH less than 7 that release more hydrogen ions than hydroxide ions Acid-carbonate reaction: A neutralisation reaction that produces salt, water and carbon dioxide gas. When a base that is a carbonate reacts with acid, bubbles of carbon dioxide gas are released Acidification: A decrease in a substance’s pH Alkali: A base that dissolves in water Base: A substance with a pH greater than 7, it has more hydroxide ions than hydrogen ions Caustic: Something that can burn or corrode Corrosive: Something that is able to damage or destroy another substance by chemical reaction Distilled water: A substance with equal numbers of hydrogen ions and hydroxide ions. Distilled water is neutral, with a pH of 7. It has been purified through a process called distillation Hydrogen ion: An ion that is released by acids in a solution Hydroxide ion: An ion that is released by bases in a solution Indicator: Any substance that changes colour when mixed with an acid or base Litmus: A dye that turns red if a substance is acidic and blue in alkaline solutions Neutral substance: A substance with a pH of 7 Neutralisation: A reaction between an acid and a base that produces a salt and water pH Scale: The standard way of measuring the strengths of acids and bases Reactive: Tending to chemically interact with other substances Solution: A type of mixture formed when one substance dissolve in another Universal indicator: A dye that turns many different colours at different pH levels Practical Components and Other: Accuracy, Reliability and Validity: Accuracy: Does your experiment complete the aim? Reliability:How often you repeat an experiment to see how often you get the same results to see if they are the same and are actually reliable Validity: This is about your apparatus, how big is your error or could you have made something in your apparatus better? Writing Scientific Reports 1. Aim: When you write your aim you are outlining what you are doing the experiment for and what you want to achieve by doing this experiment. 2. Hypothesis: The hypothesis is an educated guess on what will happen in the experiment 3. Materials: This is where you show what you used in the experiment 4. Method: This is where you outline what you did and how you did it in the experiment 5. Results: This is where you show the outcome of the experiment and you do this in a results table 6. Conclusion: This is where you finish and end the experiment. You write if your hypothesis was right or wrong and if you fulfilled the aim of the experiment

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