Science Notes PDF

Physical world Waves Waves - Transfer or spread energy - Sound and light travel as waves - Produced as a result of vibrations Parts of waves Wavelength - the distance between 2 neighbouring waves Amplitude - the maximum distance a point moves from its resting position Frequency - the num...

Physical world Waves Waves - Transfer or spread energy - Sound and light travel as waves - Produced as a result of vibrations Parts of waves Wavelength - the distance between 2 neighbouring waves Amplitude - the maximum distance a point moves from its resting position Frequency - the number of waves passing a point each second - 1 wave per second = 1 hertz(Hz) - Frequency = the number of waves passing the point/1 second Period - the time taken for a wave to complete 1 cycle - Period = 1/frequency Types of waves Transverse wave - the particles move up and down so the direction of their movement is perpendicular to the direction of the wave - Can travel through any medium(solids, liquids, gases, vacuum) - Crests : high points in a transverse wave - Troughs : low points in a transverse wave Longitudinal - the particles vibrate back and forth so the direction of their movement is parallel to the direction of the wave. - Can only travel in solids, liquids and gases. - Compressions are regions of high pressure due to particles being close together. - Rarefactions are regions of low pressure due to particles being spread further apart. The higher the amplitude, the louder the sound The shorter the wavelength, the higher the frequency, the higher the pitch of the sound, the more dangerous. Wave equation The speed of a wave through a particular substance depends on its wavelength and frequency.  V = Fλ V = speed of the wave(m/s) F = frequency of the wave (Hz) Λ = wavelength of the wave (m) Transparent, translucent, opaque Transparent - light can pass through it Translucent - only some light can pass through it. Opaque - don’t allow any light to pass through them because the light is absorbed/refracted Reflection - The bouncing of light off a solid material - The law of reflection is - Angle of incidence = Angle of reflection Types of mirrors Concave mirrors - Converge light - They are able to focus light and direct it to the focal point Convex mirrors - Diverge light - This means they are able to spread out Refraction - The bending of light as it passes through on material to another - The amount of refraction depends on the density of the medium. The higher the density, the slower the light travels - Light travelling from a low density to a higher density bends the light towards the normal. Lenses Concave lenses - are thinner in the middle and thicker at the edges - diverge/spread out Convex lenses - thicker in the middle than at the edges - The light rays converge/come together at focus Relationship between reflection and colour The colour of a material depends on the light that it reflects. If an object is red, then it reflects the red wavelength of light. Visible spectrum - The separation of white light into its component colours as a result of reflection is called dispersion - The colour sequence is ROY-G-BIV Electromagnetic waves - waves that are created as a result of vibrations between and electric and a magnetic field. - Do not require a medium - Can move through a vacuum Functions of the eye Cornea - performs the initial refraction onto the lens, which further focuses the light onto the retina Optical nerve - relay messages from your brain to create visual images Lens - works together with cornea to focus light correctly on the retina. Pupil - Changes size to let light into the eye. It gets smaller in bright light and larger as the amount of light decreases Iris - works with the pupil by opening/closing around the lens to allow different amounts of light into the eye. Retina - converts light entering your eye into electrical signals your optic nerve sends to your brain which creates images. Focusing muscle - controls the focusing of the eye and can change the thickness of the lens and curvature of the lens allowing it to move in all directions. Blind spot - In this area there are no light sensitive cells so this part of your retina can’t see. Chemical world Atoms and the periodic table Atoms - made up of subatomic particles - Protons: positively charged - Neutrons: neutrally charged - Electrons: negatively charged Neutrons - Changing the number of neutrons makes the atom - Heavier - Lighter - Sometimes unstable Protons - The number of protons an atom has determines the type of atom it is. Electrons - The number of electrons an atom has = the number of protons an atom has. Atomic mass - the sum of the number of protons and the number of neutrons in an atom Atomic number - the number of protons in an atom Element - a pure substance made up only of one type of atom Isotope - an atom of an element that has a different number of neutrons than the usual number. Ion - a charged atom - The number of protons is not equal to the number of electrons Element groups Valency - an element’s power to combine with other atoms when it forms molecules. Valence shell - the outer shell of an atom Valence electron - the electron of the atom located in the valence shell of an atom that can be transferred/shared with another atom. Group 1: Alkali metals - Group 1 metals have 1 valence electrons - Very reactive - They are soft, shiny, malleable and good at conducting electricity. - The further they go down, the more reactive they are. Group 2: Alkaline earth metals - Group 2 metals have 2 valence electrons - They have the same properties as Group 1 but are less reactive Group 3-12: Transition metals - Transition metals are all solids at room temperature except for mercury, which is a liquid - Metals in the transition metals could have a valency of +1, +2, or even +3. Group 13 - 16: Other metals, metalloids, non metals - Group 13 elements have 3 valence electrons - Group 14 elements have 4 valence electrons - Group 15 elements have 5 valence electrons - Group 16 elements have 6 valence electrons - Groups 13-16 form a staircase. - Elements to the left of the “staircase” are metals - Elements to the right of the “staircase” are non-metals - Elements inside the “staircase” are metalloids Group 17: Halogens - Group 17 have 7 valence electrons - Halogens are the most reactive non-metal - At room temperature they are all gasses except for - Bromine: liquid - Iodine/astatine - solid Group 18: Noble gas - Group 18 has a valency of 8 electrons - This groups has a full shell of electrons, thus are very unreactive Why do atoms interact with each other? Atoms interact to achieve a full valence shell, which often involves sharing, losing or gaining electrons to form chemical bonds. Most of the elements need 8 electrons in their outermost shell in order to be stable. Groups show how many valence electrons in that column Periods show how many valence shells in that row Ion - When the number of electrons change in an atom, it becomes electrically charged. Cation - If an atom loses electrons it becomes positive. Anion - If an atom gains electrons it becomes negative. Ionic compounds - are charged particles formed when an atom gains/loses electrons - Forms between a metal and non metal - Forms between a cation and an anion A metal atom loses electrons to form a cation with a positive charge. A non metal atom gains electrons to form an anion with a negative charge. Example: Magnesium 2+ + Nitrogen 3- = Mg3N2 Covalent compounds - formed when 2 non-metal atoms share valence electrons. - Shared electrons count as valence electrons for both of the atoms and so they can obtain full valence shells. Naming Ionic compounds RULE: Write cation as it is, followed by the anion with suffix - ide. Example:  Sodium and chlorine = Sodium chloride Naming Covalent compounds Mono - 1 Di - 2 Tri - 3 Tetra - 4 Penta - 5 Hexa - 6 Hepta - 7 Octa - 8 Nona - 9 Deca - 10 RULE: Get subscripts of the 2 non-metal, then put them as prefixes before the name of the elements. Put the suffix - ide to the last element Examples: N2 and O3 = Dinitrogen trioxide Nitrogen 2 and Oxygen 3 = Dinitrogen Trioxide Carbon and Oxygen2 = Carbon dioxide Chemical changes - When a substance undergoes a chemical change, a new substance is formed. - Chemical changes include, colour change, a gas(bubbles) being released, a new substance being formed, heat being released/absorbed, or a precipitate being formed - It is irreversible. Physical changes - When a substance undergoes a physical change, the substance keeps its original properties. - Physical changes include, changes of state, and other physical changes such as crushing/stretching. - It is reversible. Combustion - is a chemical reaction that produces heat and light. - It is also an exothermic reaction which means it generates heat. Word equation for Combustion is Fuel + oxygen = carbon dioxide + water + energy. Corrosion - The process by which metals are slowly broken down by reacting with substances in their environment - Only the surface of the metal corrodes due to being exposed to the substances in the environment. Rusting Iron + water + oxygen = Hydrated iron(III) oxide / rust Conditions required for rusting  - Water - Oxygen How to prevent rusting Barrier methods - preventing the conditions required 1. Paint it 2. Oil/grease it 3. Electroplating Sacrificial method - Adding a more reactive metal 1. If the reactive metal is covering the metal underneath, then the reactive metal will oxidise leaving the metal underneath clean without rusting. Precipitation reaction - a chemical reaction occurring in an aqueous solution where two ionic bonds combine, resulting in the formation of an insoluble salt Method 2: Soil pH, light intensity, and moisture Equipment: Soil probe, stopwatch, spade 1. Soften the soil by disrupting it with a spade. 2. Gently press the soil probe into the softened soil until it is at least 5 cm deep. 3. Hold the soil probe in the soil for one minute before reading the soil probe. 4. Measure the light intensity of the area around the soil. Record. 5. Measure the moisture level of the soil. Record. 6. Measure the pH of the soil. Record. Ecosystem - A community of living organisms in an area interacting with their environment. Biotic - Living things like plants, animals and bacteria - Factors influencing biotic features of an ecosystem - 1. Food availability - high food availability increase population sizes - 2. Predation - Predators reduce population size of species they attack - 3. Disease - 4. Competition - The population size of the biggest competitor will be the largest. Biotic interactions Competition - Both species are negatively affected because they compete for the same resource. The biotic components of an ecosystem involve the interactions of living things. These may include: Competition for food and water Competition for living space and shelter Competition for mating Predation, including relative abundance of predator and prey Beneficial interactions (eg. Different organisms living together for their mutual benefit) and parasitism (eg. One species living off the host without killing it) Predator-prey : The predator benefits and the prey is harmed/killed Symbiotic relationships - a close prolonged relationship between organisms of different species - These include: - Mutualism: The interaction is beneficial to both species - Commensalism: One species benefits but the other is unaffected. - Parasitism: The parasite benefits and the host is harmed. Abiotic - Non living things like temperature,light,ph levels, water, humidity, area size - Each organism has adapted to each of these factors to a certain level. - The more the organism has adapted to these conditions, the higher the population of that particular species in the area. Explain the relationship between biotic and abiotic factors in an ecosystem? Biotic factors, like animals and plants interact and depend on abiotic features such as temperature and sunlight for survival. Changes in abiotic factors can have a major impact in the ecosystem as they affect the ability of living organisms to survive in the ecosystem Food chain - The order where one organism eats another in an ecosystem. - Shows how the energy flows through the arrows. Food web - All the food chains in the ecosystem. Biomass - Chemical energy created in photosynthesis which is transferred through organisms as biomass Nitrogen cycle- Carbon Cycle- Photosynthesis - Carbon dioxide + water + sunlight = Oxygen + Sugars Biomass - Chemical energy created in photosynthesis is transferred through organisms as biomass. Trophic levels - trophic level of an organism refers to the position within a food chain - Energy is lost at each trophic level Biomass pyramid - represents the flow of energy and biomass through different trophic levels in an ecosystem - At the base there are primary producers, then primary consumers, secondary consumers and so on. What is the relationship between pyramids of biomass and energy? In a healthy ecosystem, the biomass goes down as you move up the trophic levels because the energy is being used up by the organism so, not all energy is transferred through predation. This balance ensures that populations remain stable and resources aren’t fully depleted Nervous system Stimuli - The changes in the environment to which organisms Respond and React are called Stimuli. Receptor - is a cell or a group of cells in a sense organ which is sensitive to a particular type of stimulus. Response - is our reaction or action towards a stimulus which is based in the information received from the receptors. Effectors - It can respond to a stimulus according to the information sent from the nervous system. Ex: muscles and glands The nervous system uses electrical messages to transmit information. PNS(Peripheral nervous system) - which includes all the other nerves, is responsible for detecting stimuli and initiating the response that comes from the central nervous system. - Within the Peripheral nervous system there are - Autonomic nervous system(ANS): regulates certain body processes and works automatically. - Somatic nervous system(SNS): is responsible for the voluntary actions and the somatic reflexes done by the body. CNS(Central nervous system) - made up of the brain and spinal cord, is responsible for processing the information received from the PNS. Sensory neurons - collect information from either the body’s internal environment or the outside world and send the information they have collected to the CNS. - Are only found in the PNS Interneurons - receives messages from the sensory neurons and sends response messages to the motor neurons. - Also processes incoming information and determines the response.(Processes information) - Found in the CNS Motor neurons - Carry messages from CNS to effectors which then carry out responses. - Found in PNS Explain the relationship between sensory organs, sensory neurons, motor neurons and effectors Sensory organs detect changes in the environment (stimuli) through receptors, which send signals via sensory neurons to the CNS. The CNS processes this information with interneurons and sends a response through motor neurons to effectors, like muscles or glands, which carries out the response. Brain 3 parts of the brain  - Hindbrain which consist of: - Medulla: regulates functions such as breathing, blood pressure, heart rate. - Pons: helps with some of the functions the medulla does but also coordinates signals to the rest of the brain - Cerebellum: Does the balance and movement coordination - Midbrain: involved in alertness and the sleep/wake cycle, also helps with motor activity. - Forebrain which consists of: - Cerebrum: does the speech, thinking and reasoning, sensing and emotions - Thalamus: sensory and motor information - Hypothalamus: used for hormone production in the endocrine system. Brainstem - involves medulla + pons + midbrain Endocrine system The endocrine system is a complex network of glands and organs, It produces and secretes hormones which are used to regulate various bodily functions. Hormones travel through the bloodstream and interact with target cells and tissues to maintain homeostasis. Hormones act as messengers and carry signals and instructions to target cells and tissues throughout the body through the bloodstream. They control how cells and organs do their work. They play a vital role in processes such as: - Metabolism - Growth and development - Reproduction - Stress response - Mood regulation - Organ and tissue function Hormones are produced and released by endocrine glands that bring about long term changes in the body. Hormones in the endocrine system regulate functions like growth, repair and reproduction. Other functions include Digestion and homeostasis. Role of hormones in plants Hormones play a critical role: - Growth - Development - Response to environmental stimuli - Reproduction - Stress responses The roles and interactions of the hormones vary depending on the plant species, developmental stage, and environmental conditions. Examples of hormones used in plants include: - Auxins: Primarily responsible for regulating: - Cell elongation - Stem and root development - Ensuring the main stem grows taller than the branches - Cytokinins: - Promotes cell division - Involved in various growth factors including bud growth, leaf expansion, and root development - Counterbalance effects of auxins to help maintain a balanced growth pattern - Abscisic Acid (ABA): - The stress hormone - Controls plant responses to environmental stresses e.g. drought, salinity, cold - Ethylene: - Gaseous hormone involved in fruit ripening  - Salicylic Acid: - Plays a crucial role in plant defence against pathogens The endocrine system Functions Hormonal gland Hormone Function 1. Pituitary gland Hypothalamus Releases lots of hormones that regulate conditions and acts on other glands 2. Thyroid Thyroxine Controls body’s metabolism, your weight, energy level and internal temperature 3. Thymus Thymosin Helps in the production of the cells for defence against viruses, diseases or pathogens 4. Pancreas Insulin Converts glycogen into glucose and vice versa depending on amount of glucose in the blood 5. Adrenal aldosterone Helps the kidney control the amount of salt in the blood. Produce hormones to increase energy 6. Pineal melatonin Controls day and night sleep patterns of the body. 7. Testes Testosterone Produces sperm, and other hormones relating to muscle growth, bone mass and man related hormones 8. Ovaries Oestrogen, progesterone Regulates the growth, development and secondary sexual features of the female reproductive system. 9. Parathyroid( pregnant Parathyroid hormone Regulations of calcium levels in women) the blood Homeostasis -The body's ability to maintain a stable state. Humans need to keep their body conditions stable even when surrounding conditions change. Non infectious and infectious diseases Infectious disease - caused by infections agents, e.g. bacteria, viruses, parasites, fungi Non-infectious disease - Not spread through infection or other people; caused by unhealthy behaviours or genetic abnormalities Pathogen - A pathogen is an organism or virus that causes disease to its host. Earth And Space (1-6) Continental drift theory Wegener noticed the similarity in the coastlines of eastern South America and western Africa and speculated that those lands had once formed a supercontinent, Pangaea, which had split and slowly moved many miles apart over geologic time Evidence for continental drift Evidence type Evidence How does this support? Geographic The outline and shape of our Continents were once fit current continents fit together together. like a puzzle. Geological Coal formed on the coast of These landforms where then continents. Matching split during continental drift mountain ranges with the and settled on different sides same rock type found on of the ocean. opposite sides of atlantic ocean Palaeoclimatic Large glaciers from the Demonstrates they were once perman period were found connected together. from about 240 million years ago. Palaeontological Similar fossil types of the Indicating that landmass must same age are found on have moved due to the fact different continents overseas. that living organisms couldn't possibly cross the ocean, Plate tectonics theory Describes how many landforms and landscapes are formed due to the movement of tectonic plates. I.e Phenomenon of mountains, volcanoes and earthquakes explained. Today, we know that the continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics. Evidence Sea floor spreading- Magma rises through gaps in divergent boundaries and forms a new lithosphere which subducts the old lithosphere. Seen in the diagram below. Plate boundaries- areas where plates meet and move and shift to form new landforms or earthquakes. Convergent- Where two plates are colliding against each other and later subduct. Otherwise referred to as a destructive boundary because the lithosphere is destroyed. If two continental plates collide, the crust buckles and pushes together to form fold mountains. Divergent- Where two plates move away from each other allowing magma to rise and solidify to form a new lithosphere hence the name constructive boundary. Oceanic plates form mid ocean ridges and on land a rift valley or volcano is formed. Transform- Where two plates slide past each other violently causing friction and buildup of stress and pressure causing breaks in the surface leading to earthquakes. They neither create or destroy- conservative boundaries. Forces that cause plates to move - Plates are able to move around on the asthenosphere due to slab pull, ridge push and mantle convection. And of course gravity. Slab pull- When a denser and cooler plate ( oceanic plates) than the warmer mantle subducts due to the gravity pulling the denser plate down to the earths core. Plates with long subduction zones often move faster than plates with shorter subduction zones. Ridge push- Happens at mid ocean ridges where magma rises up the gap and seeps down pulling the old lithosphere along with it like a conveyor belt. Convection currents- As the earths core heats up the rock, it rises because it is less dense. The rock in the asthenosphere drags the plate away from the middle towards the subduction zones. The convection current works as a conveyor belt slowly pulling the plates away from each other.