Year 9 Revision January Exam Revision Booklet - PDF

Year 9 Revision January exam Revision booklet  Photosynthesis Feature of plant leaf Function Plants make their own food (for energy) in a process called photosynthesis....

Year 9 Revision January exam Revision booklet  Photosynthesis Feature of plant leaf Function Plants make their own food (for energy) in a process called photosynthesis. Thin Short distance for carbon dioxide to diffuse into the leaf Photosynthesis helps keep: Waxy Layer Prevents water loss by evaporation levels of oxygen high; levels of carbon dioxide low. Palisade cells Contain a lot of chloroplasts to absorb light Chloroplasts contain Photosynthesis takes place in the chloroplasts. Absorbs light chlorophyll Chloroplasts contain chlorophyll which absorbs the energy transferred by light waves for photosynthesis Allows carbon dioxide to diffuse into the leaf (and Stomata oxygen to diffuse out) The equation for photosynthesis is: Guard cells Open/close stomata depending on conditions carbon dioxide + water → glucose + oxygen Network of tubes (xylem & Transports water (xylem) and food (phloem) phloem) These are the things that plants need for photosynthesis: carbon dioxide – absorbed through their leaves; Water - from the ground through their roots; light (a source of energy) - from the Sun. 9BP: Plants and photosynthesis These are the things that plants make by photosynthesis: Oxygen - released into the air from the leaves; Glucose: Water turned into starch and plant oils, used as an energy store; Water is absorbed through the roots, by osmosis; Food security and pollination This energy is released by respiration; It is transported through tubes (xylem) to the leaf; Pollination is the transfer of pollen from one Used to make cellulose for cell walls. The roots contain cells called a root hair cells: plant to another; They increase the surface area Pollen can be transferred by insects or by They have thin walls to let water pass into them easily. wind; They do not contain chloroplasts. Insects that pollinate plants help us produce our food. Our food supply depends on plants: Respiration v photosynthesis Our food made of, and from plants; Photosynthesis: The animals we eat feed on plants. carbon dioxide + water → glucose + oxygen Aerobic respiration is: glucose + oxygen → carbon dioxide + water Carbon dioxide The equation for photosynthesis is the opposite of the equation for aerobic Enters leaf by diffusion through the stomata. respiration. Guard cells control the size of the stomata Photosynthesis: Stomata closes in hot, windy or dry conditions. produces glucose and oxygen; Spongy layer has gaps between cells; Water is absorbed into the roots by a process called osmosis, which does not uses carbon dioxide and water; Allows carbon dioxide to diffuse to other cells in use energy. Respiration: the leaf; Minerals are absorbed into the roots by a process called active transport, which produces carbon dioxide and water; Allows oxygen produced in photosynthesis diffuse uses energy. uses glucose and oxygen; out of the leaf. The human gas exchange system Aerobic respiration Anaerobic respiration Oxygen is needed for respiration; Energy is needed for: In humans: Carbon dioxide produced in respiration needs to be removed; growth and repair The equation for anaerobic respiration in humans is: Gas exchange is moving oxygen from the air into the blood, and removing waste carbon dioxide from the blood into the air. movement glucose → lactic acid control of body temperature in mammals/birds Lactic acid builds up in the muscles; The respiratory system contains the organs that allow us to get the oxygen we need and to remove Causing pain and tiredness (fatigue); the waste carbon dioxide we do not need: The equation for aerobic respiration is: Can lead to cramp; Air passes from the mouth into the trachea (windpipe); glucose + oxygen → carbon dioxide + water Lactic acid is broken down when you start aerobic The trachea divides into two bronchi - one for each lung. respiration again. Each bronchus divides into smaller tubes called bronchioles. Glucose and oxygen react to produce carbon dioxide and At the end of each bronchiole, there are air sacs (alveoli) water and release energy; Fermentation The alveoli increase the surface of the lungs. It is aerobic respiration because oxygen is used; The equation for anaerobic respiration in yeast is: Respiration happens in all living cells, including plant and glucose → ethanol + carbon dioxide Features of the alveoli animal cells; Anaerobic respiration happens in microbes (eg Increase surface area of lungs; Takes place in the mitochondria of the cell; bacteria); Moist, thin walls (just one cell thick); Energy is released from glucose; They need to release energy from glucose; A lot of tiny blood vessels called Do not confuse respiration with breathing (which is called Yeast (unicellular fungi) can carry out an anaerobic capillaries ventilation). process called fermentation; The gases move by diffusion (from a high Ethanol (alcohol) is produced; concentration to a low concentration): The ethanol is used to make beer and wine; oxygen diffuses from the air into the The carbon dioxide helps bread rise. blood; 9BB carbon dioxide diffuses from the blood Aerobic Anaerobic into the air. Biological systems and processes Needs oxygen? Yes No Ventilation Needs glucose? Yes Yes Ventilation is another word for breathing; It involves movements of the ribs, intercostal muscles and diaphragm to move air in and out Product(s) Carbon dioxide Lactic acid of the lungs: formed and water inhale – breathing in; exhale – breathing out; Energy released More Less Impact of exercise - exercise causes an increase in: breathing rate; tidal volume (volume of air breathed in/out in one breath); Regular exercise can increase the: strength of the diaphragm and intercostal muscles; vital capacity (volume of air that can be forcibly exhaled after inhaling fully). Smoking Stimulants Smoking is very harmful to health. Smoke contains harmful substances. Stimulants speed up messages in the brain and along the nerves. These include: Drugs tar Drugs are a substance that has an effect on the body. Legal Stimulants nicotine They can be: Nicotine and caffeine are legal stimulants; carbon monoxide medicines are drugs that treat pain or disease; Caffeine is found in cola drinks, coffee and tea; recreational drugs are taken because people like the effects they Caffeine makes you feel more alert, but it can cause insomnia Tar have on their bodies. (difficulty in sleeping), headaches and nervousness; causes cancer of the lungs, mouth and throat; coats the inside of the lungs causing coughing; Some recreational drugs are legal, eg caffeine, tobacco & alcohol; Illegal Stimulants damages the alveoli, making gas exchange difficult. Most recreational drugs are illegal, eg cannabis, ecstasy and heroin; Cocaine, ecstasy and amphetamines are all illegal stimulants; Recreational drugs can be classified as a depressant or a stimulant; Cocaine, ecstasy and amphetamines make you feel more Smoke Most recreational drugs can be addictive. energetic and confident, but damage the liver and heart; Cells in the trachea, bronchi and bronchioles produce mucus; They cause loss of memory and concentration, and increase risk Mucus traps dirt and microbes; of mental illness; Cells with cilia move the mucus out of the lungs; Smoke and tar damages the cilia; Smokers cough to move the mucus and are more likely to get bronchitis. Depressants 9BB Depressants slow down messages in the brain and along the nerves; Nicotine Nicotine is addictive; Biological systems and processes alcohol, heroin and solvents are depressants Nicotine increases heart rate and blood pressure, and makes blood vessels Here are some of the typical effects depressants have on the body: narrower; Asthma feelings of well-being; This can lead to heart disease. Asthma affects the bronchioles; lowered inhibition; Airways can become inflamed, swollen and constricted slowed thinking; Carbon monoxide (narrowed); slowed muscular activity; Carbon monoxide takes the place of oxygen in red blood cells; excess mucus is produced. a distorted view of the world, or hallucinations. This reduces amount of oxygen that the blood can carry; It means the circulatory system has to work harder, causing heart disease. During an asthma attack: Long-term effects of depressants: the lining of airways becomes inflamed; damage to the liver, brain and heart; fluid builds up in the airways; alcohol can cause weight gain; muscles around bronchioles contract, which constricts solvent abuse causes a rash around the nose and mouth; Smoking and pregnancy airways. loss of memory and concentration; Smoking can damage the foetus during gestation. For example, it can: increased risk of mental illness. increase the risk of complications in pregnancy and birth; Symptoms are: make it less likely to have a healthier pregnancy and a healthier baby wheezing, tight chest and difficulty breathing. increase the risk of stillbirth; treated using drugs called relievers which relax and open up make it more likely to be born too early; Any drug that is misused can cause damage to the body, as well as the airways. be more likely to be born underweight. personal and social problems. Injecting drugs with syringes that someone else has used may Relievers are often administered using an inhaler, to breathe the lead to diseases such as HIV and hepatitis. medicine in directly into your lungs. Joints The skeleton Muscles and movement Most joints allow parts of the skeleton to move; Bone is a living tissue with a blood supply. Muscles work by getting shorter - they contract; The human skeleton has joints called synovial joints. It is constantly being dissolved and formed Muscles are attached to bones by strong tendons. It can repair itself if a bone is broken. During muscle contraction, it pulls on the bone, moving it. Calcium and other minerals make bone strong but slightly flexible. Antagonistic muscles Muscles can only pull, they cannot push; Four functions of the skeleton: Muscles work in pairs, called antagonistic muscles; 1) Support the body The skeleton supports the body. For example, without a Your elbow joint has two muscles that move your forearm up or down. These are the backbone we would not be able to stay upright. biceps and the triceps: 2) Protection of vital organs to raise the forearm, the biceps contracts and the triceps relaxes; the skull protects the brain to lower the forearm again, the triceps contracts and the biceps relaxes. the ribcage protects the heart and lungs the backbone protects the spinal cord 3) Movement Bones are linked together by joints; The synovial joint Some are fixed joints – eg in the skull; The ends of the bones in a joint are covered with a tough, smooth Some are flexible joints – eg the knee; substance called cartilage. Muscles move bones attached by joints. This is kept slippery by a liquid called synovial fluid. 4) Making blood cells Tough ligaments join the two bones in the joint; Two main types of blood cell: If two bones moved against each other, without cartilage they red blood cells, which carry oxygen; would eventually wear away; white blood cells, which destroy harmful microbes This is called arthritis. (pathogens); Both are made in the bone marrow - soft tissue inside large bones protected by the hard part of the bone around it. Muscles exert a force on bones when they contract. You could work out the force exerted by the biceps muscle using the idea of moments. 9BB The way in which muscles and bones work together to exert forces is called biomechanics. Biological systems and processes Structure of DNA Key terms Definition Genetic information is passed from one generation to the the pair of nitrogenous bases that connects the next. Base Pair This is called heredity and why we resemble our parents. (complementary) strands of DNA; Bond the chemical link that holds molecules together; The genetic information itself is contained in a complex molecule called DNA. Chromoso strands of DNA; me Scientists worked out the structure of DNA in the 1950s. Deoxyribonucleic acid. The chemical carrying the Rosalind Franklin made ‘X-ray diffraction’ images of DNA. DNA genetic code; Double the shape of DNA molecule, two strands twisted helix in a spiral; a section of DNA which we inherit from our Gene parents, and which controls part of a cell's chemistry (protein production); genetic information that determines an Heredity organism's characteristics, passed on from one generation to another. Nucleus controls what happens inside the cell, and 9BB contains chromosomes Biological systems and processes James Watson and Francis Crick used information from one Chromosomes, DNA and genes of her images to work out a model for the structure of The DNA in all of your cells is approximately two metres long, except for: DNA. Red blood cells which have none; Sperm or eggs only have about one metre. Work by Maurice Wilkins, a colleague of Franklin, supported their model. It is coiled into structures called chromosomes. Chromosomes are found in the nucleus of each cell. Human body cells each contain 23 pairs of chromosomes; Watson and Crick were able to work out how DNA was Half of which are from each parent; arranged. Human gametes (eggs and sperm) each contain 23 chromosomes; They worked out that: When an egg is fertilised by a sperm, it becomes a cell with 23 pairs of DNA has two strands; chromosomes; the strands are twisted to form a double helix; We each have half of our chromosomes and DNA come from each parent; the strands are held together by bonds between base DNA makes up genes, which makes up chromosomes. pairs. One copy of all your chromosomes is called your genome.  The 7 nutrients Energy released from food is used for things like: Stages of digestion Digestion is when large insoluble food particles are broken down into Nutrient Use in the body Good sources muscle contraction Digestion starts in the mouth, where teeth mechanically small soluble particles so that they can be absorbed into our keeping warm digest food during chewing. Chemical digestion begins here bloodstream. Cereals, bread, when the food mixes with saliva. making new cells Carbohydrate To provide energy pasta, rice and Food is swallowed as passes down the oesophagus. This is carried out by enzymes - special proteins that can break large potatoes When food reached the stomach, the food continues to be molecules into small molecules. Each person needs a different amount of energy depending on Fish, meat, eggs, factors such as: mechanically digested when the stomach muscles contract Protein For growth and repair beans, pulses and gender (male or female) to churn food. Chemical digestion also continues when the Different enzymes can break down different nutrients: dairy products age food mixes with acid and enzymes inside the stomach. Carbohydrates (eg starch) are broken down into sugar - To provide energy. Also to amount of daily activity Most digestion happens inside the small intestine when the by carbohydrase enzymes Lipids (fats store energy in the body and food mixes with enzymes and bile (chemical digestion), and Butter, oil and nuts and oils) insulate it against the cold. Energy in food is measured in kilojoules, kJ. is moved along the canal by muscle contractions (mechanical digestion) Needed in small amounts to Salt, milk (for Digested food is absorbed into the bloodstream, by Minerals maintain health calcium) and liver diffusion from the small intestine. Water is reabsorbed into (for iron) 8BD Digestion and Nutrition the body in the small intestine Undigested food passes out of the anus as faeces. Needed in small amounts to Fruit, vegetables, Vitamins maintain health dairy foods To provide roughage to help to A balanced diet contains the right energy intake and the correct amounts of necessary nutrients. Proteins are broken down into amino acids - by protease enzymes; keep the food moving through Fibre Vegetables, bran An imbalanced diet contains too much or too little of a particular the gut nutrient and/or energy. Needed for cells and body Water, fruit juice, Nutrient deficiency diseases: Water fluids milk Mineral deficiency diseases are caused when your diet is lacking in a particular mineral: Chemical food tests iron deficiency causes anaemia, where there are too few red blood cells; iodine deficiency can cause a swelling in the neck called Nutrien Chemical test Positive result goitre. Lipids (ie fats and oils) are broken down into fatty acids and glycerol t - by lipase enzymes. Vitamin deficiency diseases are caused when you diet is lacking in Starch Iodine solution Iodine solution turns from a particular vitamin: orange/brown🡪 blue black vitamin A deficiency can cause blindness; vitamin C deficiency causes scurvy, which makes the gums The role of liver and pancreas bleed; The liver produces bile, which helps the digestion of lipids Sugar Benedict’s Benedict’s solution turns vitamin D deficiency causes rickets, which makes the legs bow (fats and oil). solution & heat from: outwards in growing children. The pancreas produces biological catalysts called blue 🡪 green /yellow/brick digestive enzymes which speed up the digestive reactions. red Energy imbalances in diets Fat Ethanol & shake, Ethanol turns cloudy white If the amount of energy you get from your food is different from Absorption by diffusion across a then water & the amount of energy you use, your diet will be imbalanced: surface happens efficiently if: At very high temperatures, these enzymes will be denatured. shake the surface is thin; Digestive enzymes cannot break down dietary fibre, which is why the too little food/ energy can make you underweight its area is large. body cannot absorb it. Protein Biuret reagent Biuret reagent changes from too much food/ energy can make you overweight The inner wall of the small Minerals, vitamins and water are not digested, as they are already small blue to purple intestine is adapted. It has: enough to be absorbed. Respiration Imbalanced energy intake diseases: a thin wall, just one cell thick; Starvation happens if you eat so little food that your body many tiny villi to give a really becomes very underweight. This can eventually cause death. big surface area. The villi The digestive system contains some good bacteria which are important A chemical reaction that takes place in all living cells to contain many capillaries to because they: release the energy in food: Obesity happens when you eat so much food that your body carry away the absorbed food can digest certain substances humans cannot digest; becomes very overweight. Diseases linked with obesity include molecules. reduce chance of harmful bacteria multiplying, causing disease; Sugar + oxygen 🡪 carbon dioxide + water heart disease, diabetes, arthritis and stroke. produce vitamins that humans need eg vitamins B & K.  Parts of the microscope Unicellular organisms are made of one cell (eg bacteria) Cell Tissue Organ Organ system Multicellular organisms are made of many cells (eg plants and humans) Cell The smallest structural unit of all organisms Tissue Made from a group of cells with a similar structure and function, which all Bacteria cell work together to do a particular job Organ Made from a group of different tissues, which all work together to do a particular job Organ Made from a group of different organs, which all work together to do a System particular job Put the slide on the stage Digestive system Always start on the lowest Role: to break down large food molecules into magnification as it gives you the smaller molecules that can be absorbed widest field of vision Adaptations Use the focus to see your object The intestine is a highly folded structure, which Then increase the magnification increases surface area which speeds up diffusion The intestine is covered in many villi which are Organelle Nucleus Function Contains genetic material which controls the cell’s activities 7BC - Cells, further covered by microvilli = large surface area 🡪 faster rate of diffusion Thin membranes 🡪 shorter distance to diffuse 🡪 Cell Membrane Controls the movement of substances in and out of the cell tissues and faster rate of diffusion Covered in blood vessels 🡪 keeps blood moving Cytoplasm Where chemical reactions happen to maintain concentration differences 🡪 faster Mitochondria Where energy is released in respiration organs rate of diffusion Ribosome Where protein synthesis happens Respiratory system Role: to take in oxygen for respiration and remove carbon dioxide Cell Wall Provides strength and support Main adaptations ONLY in Chloroplast Absorb light energy for photosynthesis (contains chlorophyll) plant Trache Contains C ring cartilage which keeps the Vacuole Filled with cell sap. cells a airway open leaving a clear passage for air to travel in and out of the lungs These are some examples of specialised cells; cells that are adapted to do a specific job. Alveoli Thin membranes 🡪 reduced diffusion distance Root hair cell Good blood supply 🡪 maintains large vacuole for storing Sperm cell concentration gradients Palisade cell cell sap Highly folded membrane 🡪 increased Streamlined – swim fast lots of chloroplasts large surface area to absorb Inhaled air contains more oxygen than exhaled surface area Lots of mitochondria that that absorb sunlight water and minerals more release air. Exhaled air contains more carbon dioxide All of the above adaptation ensure that gas energy for swimming for photosynthesis efficiently than inhaled air exchange, by diffusion, happens efficiently.  Word equations to symbol equations: Bases v alkalis Reactivity Series Why do metals react? replace names of each substance symbols or A base is a substance that can react with acids and neutralise The reactivity series is a list of Metals react because they want to gain a full outer shell and formula them. Many bases are insoluble in water. If a base does dissolve elements in order of their reactivity: become stable. They do this by losing their outer electron(s) to use numbers to balance the equation become positively charged ions in water it is called an alkali Potassium Most reactive Example: Sodium For example: copper + oxygen → copper oxide Bases are usually: Calcium Magnesium loses its 2 outer 2Cu + O2 → 2CuO metal oxides, such as copper oxide Magnesium electrons to become a +2 ion metal hydroxides, such as sodium hydroxide, or Aluminium metal carbonates, such as calcium carbonate Carbon Zinc Two copper atoms (2Cu) react with one oxygen Iron General word equations for neutralisation reactions: molecule (O2) to produce two units of copper oxide Tin Lead Why do non-metals react? (2CuO) Metal oxide + acid 🡪 salt + water Non-metals react because they want to gain a full outer shell and Hydrogen Metal hydroxide + acid 🡪 salt + water Copper become stable. They do this by gaining electrons into their outer Typical properties of metals Silver shell to become negatively charged ion. Metal carbonate + acid 🡪 salt + carbon dioxide + water Appearance Shiny Gold State at room Solid (except mercury, Platinum For example: The lab test for carbon dioxide Oxygen gains 2 electrons into its temperature a liquid) Least reactive Bubble the gas through lime water and watch for it turn from outer shell to become a -2 ion Density High colourless to a cloudy milky colour. If a metal loses its outer electrons more easily, it will be more reactive. Displacement Reactions: Strength Strong Malleable or brittle Malleable This is when a more reactive metal displaces a less reactive Conduct heat? Good Acids and metals 9CR - Reactivity metal from its compound. Acids react with most metals to produce a salt and For example: Conduct electricity? Good hydrogen. This is the general word equation : Extracting copper from copper oxide magnesium + copper sulfate → magnesium sulfate + copper Magnetic material Only iron, cobalt & Copper is so unreactive, it does not react with cold nickel metal + acid → salt + hydrogen If the more reactive metal is already in the metal or hot water, so it is used for water pipes compound, nothing happens. For example: Sound when hit Make a ringing sound The lab test for hydrogen (sonorous) Place lighted splint put in the test tube and listen for To extract copper: magnesium sulfate + copper → no reaction the gas to burn with a squeaky pop mix copper oxide powder with carbon powder; Pure metals Vs Alloy heat the mixture strongly in a crucible; Carbon and metal extraction Naming salts keep the lid on the crucible, to stop carbon Some metals can be extracted from their metal oxides Hydrochloric acid 🡪 metal chlorides reacting with oxygen in the air; using carbon if the metal is less reactive than carbon. Sulfuric acid 🡪 metal sulfates the carbon dioxide formed in the reaction Nitric acid 🡪 metal nitrates The metal is reduced – escapes into the air; it has lost its oxygen let the crucible cool down, you tip the mixture Calculating relative formula mass pure metal allloy Formula mass is calculated by adding together the mass into cold water. metal oxide + carbon → metal + carbon dioxide number of each atom in a compound’s chemical formula. brown copper sinks to the bottom, leaving The rows of atoms in a pure metal can slide over unreacted powder suspended in the water. The carbon is oxidised each other easily. E.g. MgCl2 Ar Mg = 24 Ar Cl = 35.5 – it has gained oxygen In an alloy, the different sized atoms disrupt the These equations represent the reaction: layers so the atoms can’t slide. Formula mass = 24 + (2 x 35.5) = 95 copper oxide + carbon → copper + carbon dioxide This works for zinc, iron, tin, lead and copper because they This makes alloys more useful than pure metals. 2CuO + C → 2Cu + CO2 all less reactive than carbon. There are 2 chlorines in the chemical formula Atoms are tiny particles that everything Elements Compounds Chemical formulae is made of. There are over a hundred different elements. A compound is contains atoms of two or more different Remember that we use chemical symbols to stand for the elements. elements, and these atoms are chemically joined together. For example, C stands for carbon, S stands for sulfur and Na stands for sodium. They are made of smaller particles Atoms have the same number of protons as each other. called: For a molecule, we use the chemical symbols of all the atoms it contains to write down its Protons (+ positive) Atoms of differing elements have a different number of protons. For example, water is a compound of hydrogen and oxygen. formula. For example, the formula for carbon monoxide is CO. Neutrons (neutral) Electrons (- negative) The atoms of some elements do not join together, but instead they It tells you that each molecule of carbon monoxide is made of one carbon atom joined to one stay as separate atoms, eg Helium. oxygen atom. Be careful about when to use capital letters. For example, CO means a molecule of carbon monoxide but Co is the symbol for cobalt (an element). Each of its molecules contains two hydrogen atoms and one Each element is given its own chemical symbol, like H for hydrogen or O for oxygen. The atoms of other elements join together to make molecules, eg oxygen atom. oxygen and hydrogen. Chemical symbols are usually one or two letters. The elements are arranged in a chart called the periodic table. Every chemical symbol starts with a capital letter, with the second letter written in lower A Russian scientist, Mendeleev, produced the first periodic case.For example, Mg is the correct symbol for magnesium, but mg, mG and MG are wrong. Metals have properties in common. They table in the 19th century. are: shiny, especially when they are The modern periodic table is based closely on the ideas he freshly cut used: good conductors of heat and the elements are arranged in order of increasing atomic electricity Most metals also have other properties in common. They are: number (number of protons); malleable (they can be bent and solid at room temperature, except mercury; the horizontal rows are called periods; Numbers in formulae shaped without breaking) hard and strong; the vertical columns are called groups; We use numbers to show when a molecule contains more than one atom of an element. they have a high density; elements in the same group have the same number of electrons in their outside shell The numbers are written below the element symbol. For example, CO2 is the formula for carbon dioxide. We can use the periodic table to predict the properties of elements in the same group. 8CP: Periodic Table It tells you that each molecule has one carbon atom and two oxygen atoms. The small numbers go at the bottom. For example: Group 7 Melting point Density Reactivity CO2 is correct; Fluorine CO2 and CO2 are wrong. Increases Decreases Group number Chlorine Increases down down the down the the group group group Bromine Iodine Group 1 Melting point Density Reactivity Lithium Periods Increases Increases Sodium Decreases down down the down the the group group group Potassium Some formulae are more complicated. For example, the formula for sodium sulfate is Na2SO4. It tells you that sodium sulfate contains two sodium atoms (Na x 2), one sulfur atom (S) and four Rubidium oxygen atoms (O x 4). Chemical reactions Chemical equations Symbol equations When chemicals react, the atoms are rearranged. For example, iron reacts with We summarise chemical reactions using equations: sulfur to make iron sulfide A balanced symbol equation includes the symbols and formulae of reactants → products the substances involved. For example: Reactants are shown on the left of the arrow; Word equation: Products are shown on the right of the arrow. Copper + Oxygen → Copper Oxide Do not write an equals sign instead of an arrow. Symbol equation (unbalanced): Cu + O2 → CuO If there is more than one reactant or product, they are separated by a + sign. For example: There is one copper atom on each side of the arrow, but two oxygen atoms on the left and only one on the right. This is copper + oxygen → copper oxide unbalanced. Reactants: copper and oxygen A balanced equation has the same number of each type of atom Iron sulfide, the compound formed in this reaction, has different properties to the Products: copper oxide on each side of the arrow. Here is the balanced symbol equation: elements it is made from. A word equation shows the names of each substance 2Cu + O2 → 2CuO Sulfur Iron sulfide involved in a reaction, and must not include any Iron chemical symbols or formulae Type of substance Element Element Compound Colour Silvery grey Yellow Black Is it attracted to a magnet? Yes No No 8CP: Periodic Table Hydrogen sulfide Reaction with hydrochloric formed, which acid Hydrogen formed No reaction smells of rotten Conservation of mass eggs When atoms are rearranged in a chemical reaction, they are not destroyed or created. Some more examples of balanced symbol equations C + O2 → CO2 The atoms in a compound are joined together by forces called bonds. 2H2 + O2 → 2H2O Reactants - the substances that react together; The properties of a compound are different from the elements it contains; 2Mg + O2 → 2MgO Products - the substances that are formed in the You can only separate its elements using another chemical reaction; CuCO3 → CuO + CO2 reaction; Separation methods like filtration and distillation will not do this. Mg + 2HCl → MgCl2 + H2 Mass is conserved in a chemical reaction, this means… Total mass of the reactants = total mass of the products; Take care when writing formula – e.g. for carbon dioxide: CO2 NOT CO2 or Co2  Explaining the properties of solids Explaining the properties of liquids Explaining the properties of gases Property Reason Property Reason Property Reason Fixed They flow and Particles cannot move from place They flow and shape & take the shape The particles can move around each other to place completely fill their The particles can move quickly in all directions cannot flow of their container container Cannot be They cannot be The particles are close together and have They can be compresse Particles are close together and compressed The particles are far apart and have space to no space to move into compressed d have no space to move into (squashed) move into (squashed) (squashed) Gas Pressure Diffusion Particles When gas particles hit the walls of their container, they cause pressure. The faster the particles move, the higher the gas pressure. Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. Diffusion happens in liquids and gases because their particles move randomly from place to Conservation of mass place. The particles stay the same when a substance changes state - only their closeness, arrangement or motion change. This means that the mass of the substance stays the same. For example, 10 g of water boils to form 10 g of steam, or freezes to form 10 g of ice. This is called conservation of mass. Gaining energy Losing energy Gaining energy melting Boiling (or evaporating) Condensing Freezing Melting Evaporating or boiling Description Gas to liquid Liquid to solid Description Solid to liquid Liquid to gas Closeness of Become much closer Stay close together Closeness of Stay close particles together Become much further apart particles together Arrangement Stay random Random to regular Arrangement Regular to of particles Stay random of particles random Stop moving quickly in all Stop moving around Freezing Condensing Motion of Motion of Start to move Start to move quickly in all directions, and can only each other, and only particles move around each other vibrate on the spot Losing energy particles around each other directions A pure substance contains only one type of particle. A mixture contains more than one type of particle that are not chemically joined together. For example: Particles For example: Pure iron contains only iron particles (called iron atoms); Steel contains iron particles and small amounts of carbon particles (called carbon atoms); Pure water contains only water particles (called water molecules); Tap water contains water particles and small amounts of other particles (called ions); Pure oxygen only contains oxygen particles (called oxygen molecules). Air contains 21% oxygen, 78% nitrogen and 1% of other gases (eg argon and carbon dioxide). We can separate mixtures Dissolving is one way to make a mixture. For example, when salt is stirred into water, the salt in different ways depending dissolves in the water to make salt solution. Chromatography is a method for separating on their properties: dissolved substances from one another. In a solution: Filtration the substance that dissolves is called the solute; It works because some of the coloured Evaporation the substance that the solute dissolves in is called the solvent. substances dissolve better than others, so they Chromatography Distillation E.G In salt solution, salt is the solute and water is the solvent. travel further up the paper. When you can’t dissolve any more solute in a solvent, we say the solution is saturated. Filtration is a method for separating an insoluble Evaporation is used to separate a soluble solid from Distillation is a method for separating the solvent from solid from a liquid. a liquid. a solution. When a mixture of sand and water is filtered: For example, copper sulfate is soluble in water – its For example, water can be separated from salt solution the sand stays behind in the filter paper (it crystals dissolve in water to form copper sulfate because water has a much lower boiling point than salt. becomes the residue); solution. When the solution is heated, the water evaporates. It is the water passes through the filter paper (it then cooled and condensed into a separate container. becomes the filtrate). During evaporation, the water evaporates away The salt does not evaporate and so it stays behind. A pencil line is drawn, and spots of ink or dye are leaving solid copper sulfate crystals behind. placed on it. There is a container of solvent (eg water or ethanol). As the solvent continues to travel up the paper, the different coloured substances spread apart. A chromatogram, the results of chromatography experiment. The pH scale Conservation of mass Oxidation reactions Solutions can be acidic, alkaline or neutral: Oxidation reactions are when a substance reacts and joins with Acidic solutions form when acids dissolve in water; Alkaline solutions form when alkalis dissolve in water; Total mass = Total mass oxygen. Solutions that are neither acidic nor alkaline are neutral of reactants of products An example of this is where metals react with oxygen to make metal Pure water is neutral. oxides. We say that mass is conserved in metal + oxygen 🡪 metal oxide Universal indicator can tell us how strong acidic or alkaline a solution is. This is measured a chemical reaction. E.g. magnesium + oxygen 🡪 magnesium oxide using the pH scale, which runs from pH 0 to pH 14: Another example is a combustion reaction, where we burn fuels in oxygen: Fuel + oxygen 🡪 carbon dioxide + water Chemical We can represent theses reactions using WORD EQUATIONS The substances that react together are called the reactants The substances that are formed in the reaction are called the products Reactions The 🡪 shows that we are making something new The closer to pH 0 you go, the more strongly acidic it is; Reacting metals with acids The closer to pH 14 you go, the more strongly alkaline it is. metal + acid 🡪 metal salt + hydrogen Hazard signs to be aware of when dealing with acid and Neutralisation E.g. zinc + hydrochloric acid 🡪 zinc chloride + hydrogen alkalis: When an acid reacts with an alkali (or base), a neutral salt solution is formed. This is called neutralisation. Corrosive Irritant acid + alkali → salt + water To test if hydrogen is produced, hold a lit splint to the gas and eg sodium hydroxide + hydrochloric acid → sodium chloride + water listen for it to burn with a squeaky pop. Naming salts From an alkali containing potassium, eg potassium hydroxide Second name of The name of a salt has two parts: Acid used salt ❖ The first name comes from the metal in the alkali used. ❖ The second name comes from the Potassium nitrate hydrochloric acid sulfuric acid chloride sulfate acid that was used. From the acid “NITRIC ACID” nitric acid nitrate Change of state Pressure in fluids Atmospheric pressure Substances can change state, usually when they are heated or cooled; A fluid is a liquid or gas. The atmosphere exerts a pressure on you, and everything State changes are reversible – eg ice can be melted and then frozen again; All fluids can change shape and flow from place to place. around you. No new elements or compounds are formed. Fluids exert pressure at 90° to surfaces – we say that it acts normal to the surface. Atmospheric pressure changes with altitude. The higher you go: The closeness, arrangement and motion of the particles in a substance change when it the lower the weight of the air above you; changes state: Brownian motion the lower the atmospheric pressure. Gas particles move very quickly; Solid Liquid Gas Air particles move at 500 m/s on average at room Pressure in liquids temperature; Just like the atmosphere, liquids exert pressure on objects. Closeness All touching Mostly touching Far apart Particles collide with each other very frequently; They change direction randomly when they collide; The pressure in liquids changes with depth. The deeper you go: Their random motion because of collisions is called Brownian the greater the weight of liquid above Arrangement Ordered Random Random motion. the greater the liquid pressure Motion Vibrate, fixed Move freely Move freely Diffusion position (faster than Diffusion is the movement of particles from an area of high Pressure in a liquid increases liquids) concentration to an area of low concentration. with depth; Diffusion does not happen in solids – only fluids (liquids and Jet from the bottom of the Density Decreasing density -------------------------------------------------> bucket travels further. gases); Particles in a solid can only vibrate and cannot move from Internal Increasing internal energy ---------------------------------------> place to place. energy Diffusion is driven by differences in concentration; No diffusion will take place if there is no difference in Floating and sinking concentration from one place to another; Liquid pressure is exerted on surfaces of objects in liquids; Diffusion in liquids is slower than diffusion in gases because This causes upthrust; 9P