S2 Chemistry. materials. do not write on these sheets

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1 S2 Chemistry materials do not write on these sheets 1

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4 MATERIALS Any substance can be described as a SOLID, LIQUID or a GAS. These are called the THREE STATES OF MATTER. 1. Solids Imagine you are building a house and you make a list of all the things you need: bricks, wood, glass, pipes, roof tiles All these have something in common. They are hard and keep their shape. They are called solids. Fraser wants to hammer a nail into a piece of wood. He uses a hammer or a stone because they are both hard solids. 1. Copy and complete the table below in your jotter. 2. Draw any solid and write a description about it. 4

5 Liquids If you want to wash a kitchen floor or a car there a several substances you could use water, disinfectant, washing-up liquid, bleach All these have something in common. They are runny and wet and flow wherever they can. They are called liquids. They take up the shape of the container into which they are poured. Heather wants to clean mud from a path. She uses a hose and sprays it with water. Water is a liquid. Liquids spread out to cover a surface. 1. Copy and complete the table below in your jotter. 2. Draw any liquid and write a description about it. 5

6 Gases We all have to breathe to stay alive. We breathe in many substances nitrogen, oxygen, argon, carbon dioxide These substances are called gases. They spread out to fill all the spaces they can find. Gases fill the containers in which they are kept. Many gases, like those found in air, are invisible. Frank has a puncture. To find the hole, he pumps the tube full of air to blow it up. Air is a gas. Gases spread out to fill all the space they are given. When a gas tap is left on in the lab, the whole class can soon smell gas. This is because the gas fills the whole room. If you left the water tap on, only the floor would get wet. Liquids spread out to cover a surface only, but a gas can go anywhere. 1. Copy and complete the table below in your jotter. 2. Write a description about any gas you choose. 6

7 2. Particles All substances are made from particles. The way in which these particles are: Arranged How they move How close they are to their neighbours Solids explains why they behave the way they do. Solids have a fixed shape and cannot flow. Particles are only able to vibrate about a fixed position. They cannot move from place to place. solid Bonds between particles are strong and so keep the particles stuck together. Liquids Liquids flow and take the shape of their container. When water is poured into a glass, the particles of water are still close together but can move over each other. They keep on moving over each other as the water takes the shape of the glass. liquid The bonds between the particles are strong but weak enough to let them move around each other. Gases Gases flow to fill their container and to take its shape. This is because there are no bonds between the particles and so they can move in all directions. When a bunsen burner is turned on, particles of gas are free to move anywhere inside the tubing. The pressure forces them through the tubing and into the bunsen. gas 7

8 Particles: Activity Cut out all of the nine diagrams from handout 1 2. Draw a table with three headings in your jotter : SOLIDS, LIQUIDS & GASES. 3. Place the diagrams under the correct heading. Get your teacher to check your answers before sticking them in. Activity Now cut out all the 20 boxes from handout 2 2. On the same table, place these boxes under the correct heading. 3. Get your teacher to check your answers before sticking them in. QUESTIONS: Explain: 1. How ice is different from water. 2. Why you can walk on a frozen pond. 3. Why water is runny. 4. Why a car tyre goes flat if a nail makes a hole in it. 5. Why a balloon gets bigger as you blow more air into it. 8

9 handout 1 handout 1 9

10 handout 2 Particles Are free Particles Are free Particles moving fast in all Will always keep its shape To move To move directions Will always keep its shape Will always keep its shape Will not flow Particles are vibrating Will not flow Will keep the same volume Particles moving about changing places Will keep the same volume Takes the shape of its container Takes the shape of its container Particles moving about changing places Can flow easily Can flow easily Particles fixed in a regular pattern Particles unable to move over each other Will keep the same volume handout 2 Particles Are free Particles Are free Particles moving fast in all Will always keep its shape To move To move directions Will always keep its shape Will always keep its shape Will not flow Particles are vibrating Will not flow Will keep the same volume Particles moving about changing places Will keep the same volume Takes the shape of its container Takes the shape of its container Particles moving about changing places Can flow easily Can flow easily Particles fixed in a regular pattern Particles unable to move over each other Will keep the same volume 10

11 3. changes of state Substances can be changed from one state into another state by Heating or Cooling. 1. HEATING: Solid to Liquid The more energy particles have, the more they can move around. Particles in solid chocolate or ice or gold do not have much energy. This is why they are hard. The particles in water or runny chocolate or molten gold have more energy to move about. We must supply energy to change ice into water or chocolate into a sticky mess. We have to give the particles enough energy so that they can slide about. Heating a solid gives the particles more energy causing them to move faster. This extra energy weakens the bonds between the particles causing the solid to melt. heat melting 1 melting 2 melting 3 Pure ice melts into water at 0 o C. This is the melting point of water. Chocolate melts at about 35 o C. We say that chocolate has a higher melting point than ice. Wax in candles melt at 50 o C Metals, like aluminium and iron, have to be very hot to melt. They have very high melting points. Aluminium melts at 600 o C Iron melts at 1,500 o C Tungsten melts at 3,400 o C! If the temperature around a solid is higher than its melting point, then the solid will melt. Explain in terms of energy what is happening in the diagram shown left. Icebergs getting smaller 11

12 changes of state 2.HEATING: Liquid to Gas The particles in water or molten gold have more energy to move about. If even more energy is supplied to these liquids, the particles have enough energy to move much faster. They can break the bonds between their neighbours and fly away. They have turned into a gas. heat boiling 1 boiling 2 A liquid evaporates when it turns into a gas. 3. COOLING: Gas to Liquid Particles in a gas have so much energy that they move about very quickly indeed. When we cool something we take heat away from it. When the gas is cooled down, the energy of the particles decreases. This causes the particles to move much more slowly. cool condensing 1 condensing 2 A gas condenses when it turns into a liquid. Explain in terms of energy what is happening in the two diagrams shown left. Hair dries Bus windows mist up in winter 12

13 changes of state 4. COOLING: Liquid to Solid Particles in a liquid have enough energy to move about by sliding over each other. When the liquid is cooled, the energy of the particles decreases. Particles now move much more slowly. They are now fixed in position. New bonds form between particles and the liquid turns into a solid. freezing cool A liquid freezes when it turns into a solid. bill nye phases of matter Icicles forming on trees Explain in terms of energy what is happening in the diagram shown left. 13

14 changes of state: solid to liquid Activity Put on your safety goggles. 2. Put a few crystals of the solid into the test tube. 3. Put this test tube into a beaker of water. 4. Heat the water with the bunsen burner but don t let it boil. 5. Watch carefully to see what happens to the solid. 6. Write an account of your experiment using the headings Aim, Method & Results. changes of state: liquid to gas Activity Put on your safety goggles. 2. Half fill a beaker with water and put it on the tripod stand. 3. Light the Bunsen burner and heat the water but don t let it boil. Turn off the bunsen. 4. Put FIVE drops of the liquid into the test tube. Place a cotton wool plug onto the tube. 5. Put the test tube into the hot water. 6. Watch carefully what happens to the liquid. 7. Write an account of your experiment using the headings Aim, Method & Results. Questions 1. What happened when the a) solid and b) the liquid were heated up? 2. Give everyday examples of each of these changes of state. 14

15 changes of state: gas to liquid Activity Make sure you keep your test tube from the last experiment. 2. Put some ice into a different beaker. 3. Put your test tube containing the gas into the ice and stir it around. 4. Watch carefully what happens inside the test tube 5. Write an account of your experiment using the headings Aim, Method & Results. Questions 1. What happened when the gas was cooled down? 2. Give an example of this change of state. 4. changes of state: The Water Cycle Water is the only substance that can be found naturally on the Earth as a liquid, a solid (ice) or a gas (water vapour). Water moves around the environment in a recycling process known as the Water Cycle. 15

16 changes of state: The Water Cycle Activity Collect handout 3 2. Fill in the blanks from 1 to Stick your handout into your jotter. Activity Cut out all of the 20 labelled statements from handout 4 2. Write out four headings in your jotter as shown below: MELTING, EVAPORATING, FREEZING & CONDENSATION. 3. Place the labels under the correct heading. Get your teacher to check your answers before sticking them in. Questions Explain why: 1. It takes longer for towels to dry outside than towels that are held in front of a fire. 2. You feel cold standing about after you have been swimming. 3. Boiling potatoes have been burnt below 16

17 handout solid water cycle handout solid water cycle

18 handout 4 ice cubes ice lolly paint dew on the disappearing dripping drying morning grass water on kitchen tiles next to a kettle tippex covering up mistakes pond becomes a skating rink juice forming a slush puppy windows mist up puddles clothes after a shower fog disappearing drying snow preparing water blow drying hailstones forming to make tea your hair forming on a cold day we see our breath runny ice cream nail varnish hardening frosty windows in the morning handout 4 ice cubes ice lolly paint dew on the disappearing dripping drying morning grass water on kitchen tiles next to a kettle tippex covering up mistakes pond becomes a skating rink juice forming a slush puppy windows mist up puddles clothes after a shower fog disappearing drying snow preparing water blow drying hailstones forming to make tea your hair forming on a cold day we see our breath runny ice cream nail varnish hardening frosty windows in the morning 18

19 changes of state: The Water Cycle. Warm damp air is full of water vapour. The air stays clear as long as the water is all vapour. However, the higher you go the cooler it gets. The vapour condenses into a fine mist of water droplets held up (suspended) by the air - better known as clouds. water cycle 1. Winds carry the warm damp air upwards. 2. The droplets are swept up by the climbing air. 3. They collide and bump into each other. 4. They combine to make bigger drops. 5. Eventually they get so big and heavy they start to fall as rain or snow. 6. Rain water runs over the land and collects in lakes or rivers, which take it back to the sea. 8. The cycle starts all over again. Activity 4.2 Use the information given above to fill in the boxes on handout 5 bill nye the water cycle 19

20 The Water Cycle insert handout 5 here 20

21 5. solutions: no lumps Tap water doesn t taste of anything, but sea water and swimming pool water taste awful. That s because there is stuff in the water. Sea water is salty. You can taste the salt in the water. Swimming pools have chlorine in the water which kills germs and nips your eyes. You can t see chlorine in the pool. You can t see salt in the sea. Both the chlorine and the salt mix completely in the water to make solutions. Fizzy drinks are also solutions. It looks just like a single liquid, without any lumps in it. It is mostly water with sugar, flavourings, colouring and gas in it. When you pour it out some of the bubbles of gas escape out of the solution. dissolving You make a solution by dissolving one thing in another. As you stir a teaspoonful of sugar into a glass of water, the sugar seems to get less and less. Looking through a magnifying glass you will see the little lumps of sugar go soft at the edges and get smaller and smaller. fountain experiment When the lumps have disappeared you have a sugar solution. It just looks like pure water. A liquid (water) has dissolved the solid (sugar). The substance that dissolves is called the solute. The liquid which dissolves it is called the solvent. Questions a) What is a a) solute b) solvent c) solution? b) Which of these are solutions? Sea water, fresh water, Irn Bru, sugar, mercury, lemonade, oil. 21

22 solutions: water as a solvent For a solid to be dissolved easily, we need the correct solvent. Dirty clothes are washed in hot water as the solvent for the dirt, dissolving it which is then washed away. (Soap powder is added to help the water dissolve the dirt). However, hundreds of solids (and liquids) will not dissolve in water. e.g. plastic, metals, inks, cotton wool, etc. This experiment lets you find out which substances dissolve in water. A list of stuff (solutes) dissolved in bottled water Activity Put about 3cm of water in a test tube. 2. Add a very small amount of substance into the test tube. 3. Shake the tube from side to side 4. Look carefully. Has the substance dissolved? Have any other changes taken place? 5. Copy & complete the table below. Put your results in it. 6. Write an account of your experiment using the headings Aim, Method & Results. 22

23 solutions: solvents other than water Certain solids do not dissolve in water. A different solvent is needed to dissolve them. So how is grass, blood or coffee stains removed from clothes if warm water will not dissolve them? This is when a different solvent, other than water, is used. This experiment lets you find out which solvents can dissolve nail-varnish. Activity Collect a slide with streaks of nail-varnish on it. 2. Put only one drop of a solvent onto the cotton bud. 3. Try to remove the nail-varnish streak using the bud. 4. Count how many strokes it took to dissolve the streak. 5. Copy & complete the table below. Put your results in it. cotton bud 6. Write an account of your experiment using the headings Aim, Method & Results. solvent used number of strokes to remove it Questions a) How did you make this a fair experiment? b) Which of your solvents would make good nail-varnish removers? 23

24 6. solutions: crystals A crystal is a solid whose particles are arranged in a 3-D repeating pattern. Computer processors are made from pure silicon crystals Keys are mostly iron crystals. Gold wedding rings are crystals. Accurate clocks have vibrating quartz crystals in them. Diamonds, rubies, sapphires and emeralds are very expensive and beautiful crystals. But they can also be found in your kitchen in the form of sugar and salt! Liquid crystals, can act as both as a liquid and as a crystal. They are ordered like a solid crystal in two directions, but not in a third. This allows them to flow like a liquid. They are used to create a Liquid Crystal Display (LCD) in calculators and flat-screen TVs. Crystals can be grown by making a type of solution called a saturated solution. concentrated solution If you put lots of sugar in your tea it ll taste really sweet. We say it is a concentrated solution. There is a lot of solute dissolved. If you add even more sugar it will stop dissolving. No more solute can dissolve. We now have a saturated solution. We need a saturated solution if we are to make crystals. saturated solution Activity 6.1 step one: making the saturated solution 1. Put 50cm 3 of water into a beaker. 2. Add one spatulaful of copper sulfate. Stir until all the solute is dissolved. 3. Repeat Step 2 until no more will dissolve. Copper sulfate crystals are easy crystals to grow. Here's how you can grow copper sulfate crystals yourself. 4. Transfer the beaker to a tripod stand and heat up the contents using a Bunsen. Stop heating just before it boils. 5. Add another spatulaful of copper sulfate and stir until all is dissolved. 6. Repeat Step 5 until no more will dissolve. You have now made a saturated solution. 24

25 solutions: crystals Activity 6.2 step two: crystallisation 1. Now tie a seed crystal to a piece of thread. 2. Hang the thread with the crystal dipping into the middle of your saturated solution as shown. 3. Leave it until the next day. 4.Write an account of your experiment using the headings Aim, Method & Results. Draw the size and shape of the crystal produced. (Use a coloured pencil) Making crystals, known as crystallisation, is very important to a chemist. It is used to make substances very pure. The more you crystallise a substance (recrystallise) the purer it becomes. Sugar cane and medicines such as penicillin, aspirin and insulin all have to be recrystallised. Gold is made up of billions of gold atoms stuck together Sodium chloride (salt) crystal made up of billions of sodiums and chlorides stuck together 1. Read Page 84 Starting Science Book 2 & answer Questions 1 to Read Page 85 about Crystallisation & answer questions 1 to 5. 25

26 7. mixtures Mixtures contain different substances jumbled up together. Mixtures can be separated again by methods such as sieving, filtering, evaporating etc. Mixtures can be made up of: solid in a solid eg MUESLI insoluble solid in a liquid eg MUDDY WATER solid in a gas eg SMOKE liquid in a liquid eg MILK (emulsion) liquid in a gas eg CLOUDS gas in a solid eg PUMICE STONE soluble solid in a liquid eg SALT WATER gas in a liquid eg OXYGEN IN WATER gas in a gas eg AIR Write down the substances that make up the following mixtures. The first one has been done for you 1. Mayonnaise - a liquid in a liquid (oil in water) 2. Chocolate chip cookies 3. Cornflakes in milk 4. Air freshener 5. Dirty snow 6. Smog 7. Brass 8. Lynx deoderant 9. Sugary tea 10. Oil slick 26

27 Separation processes insert handout 6 here 27

28 separating mixtures: evaporation There are about 35 kilograms of salt in every cubic metre of sea water! Hot desert countries get the salt by leaving the sea water in shallow pools. The heat from the baking sun evaporates the water leaving the salt crystals behind. Evaporation separates a soluble solid from a liquid. Sea water pumped into shallow pool Sun evaporates water leaving salt crystals Salt scraped from bottom of pool Activity Put 50cm 3 of water into a beaker. 2. Add one spatulaful of salt. Stir until all the solute is dissolved 3. Repeat Step 2 until no more will dissolve. You have now made a saturated salt solution. 4. Pour the contents of the beaker into an evaporating basin. 5. Heat the basin until only a small amount of liquid remains. 6. Turn the Bunsen off. Wait and watch what happens. 7. Once the basin has cooled down, collect your salt crystals. water evaporating salt crystals forming very hot solution Explain in detail how you could recover all of the dissolved sugar shown left. Oh no! All the sugar s dissolved in the wet bowl 28

29 separating mixtures: distillation The previous experiment enabled us to obtain solid salt from sea water. However, in many countries, it is much more important to get pure water from poisonous sea water. Distillation separates a solvent from a solution. Humans can live for weeks without eating food but can only last a few days without water. All living things have a lot of water in them. We lose a lot of water by sweating, breathing and going to the toilet. Half of this water is replaced by the food we eat. The rest has to be replaced by the water we drink. 70% water Our drinking water comes from the tap. But in parts of the world drinking water is difficult to find. The planet is covered by 75% of water but this cannot be drunk because there is so much salt dissolved in it. The set-up below shows how to get pure water from salty seawater. Activity 7.2 : teacher demonstration When the solution (sea water) is heated, the water evaporates. The hot water vapour (steam) passes through the delivery tube. It is then cooled down using a cold wet glass cylinder called a condenser. The water vapour cools down and condenses, trickling out. The salt does not evaporate. It is left behind as a solid in the flask. Arrgh! Water, water everywhere but not a drop to drink! Explain how you could turn poisonous seawater into fresh drinking water distillation 29

30 separating mixtures: filtration Filtration is a separation process in which a mixture is passed through a filter. One substance passes through this filter barrier but the other one is blocked. Filtration sorts by size. Smaller particles go through but larger particles get trapped. Examples being a colander separating spaghetti from water and a coffee filter trapping coffee beans while water passes through. Filtration is used to separate an insoluble solid from a liquid Activity 7.3 You will make your own insoluble solid. Then you will separate this new solid from the solution. 1. Measure 20cm 3 of potassium iodide solution into a 100cm 3 beaker. 2. Add 20cm 3 of lead nitrate solution to the same beaker. 3. Stir this mixture well. 4. Set up the apparatus as shown right. 5. Transfer small amounts of the mixture into the filter funnel very carefully. 6. Repeat Step 5 until the beaker is empty. 7. Write an account of your experiment using the headings Aim, Method & Results. filter paper clamp stand filter funnel beaker filtration Filtration can be used to also separate a solid from a gas. Pollen or dust can be removed by using an air filter like the ones found in cars or a simple mask that covers your nose and mouth. Explain in detail how you would solve the two problems shown left. Hoi! There s glass in my soup! Ugh! There s mud in this drinking water 30

31 separating mixtures: chromatography A prism separates sunlight into many different colours - it forms a rainbow. Like sunlight, chemical mixtures can also be separated into the parts that make them up. This process is called paper chromatography. Chromatography is a superb technique used in: Forensic science (for identifying samples taken from crime scenes), Pollution monitoring (for unknown pollutants in air and water samples), Studying complex mixtures (in food, perfume, oil and drug production) A big advantage is that only tiny samples and low concentrations are needed. Separating dissolved solids The solids found in mixtures such as food colourings, plant dyes and inks in coloured pens can be separated. Your task is to find out which colours make up black ink in a coloured pen. Activity 7.4 Chromatography separates dissolved substances from one another. 1. Measure 10cm 3 of water using a measuring cylinder. Add the water to a 100cm 3 beaker 2. Using a pencil, draw a faint line across the paper 2cm from the bottom of the paper. 3. Add a spot of ink to the paper. 6. Allow the water level to move up the paper. 4. Attach the paper to a wooden splint so that it stands up in the beaker. 5. Carefully put the paper into the beaker of water. 7. Remove it when the water has moved up about 3/4 the height of the paper. chromatography* 8. Write an account of your experiment using the headings Aim, Method & Results. One of those blue cars has bumped into mine! It has left a blue streak on my car. Explain in detail how I could find out which car was to blame. 31

32 8.global warming: the greenhouse effect Air is also a mixture of different gases. The main ones are Nitrogen (78%), Oxygen (21 %) and Argon (almost 1 %) and a tiny amount of carbon dioxide, CO 2. CO 2 is very important to green plants which absorb CO 2 together with water and energy from sunlight to make their own food. So do the plants use up all of the CO 2? No. Humans and all other animals breathe out CO 2. It is also produced in vast quantities when fossil fuels like petrol, diesel, gas, coal and oil are burned. The destruction of the forests is another reason. Trees, other plants and algae absorb CO 2, but nowhere near as fast as it is now being produced, so CO 2 levels in the atmosphere is slowly but steadily increasing. AIR nitrogen oxygen argon CO 2 in the air keeps the Earth warm. If there was no CO 2 then our planet would be very cold, about minus 20 O C! It acts like a blanket preventing too much heat being lost from the Earth s surface. This trapping of heat energy is called the Greenhouse Effect. Temperatures around the world are now rising steadily. This may be due to the rise in CO 2 levels and is known as Global Warming. Global warming doesn t mean that everywhere would become hotter. Some places would actually become colder. Some would get wetter and others drier. Extreme events such as heavy rains and droughts are expected. The level of the seas will rise because water expands as it gets hotter and also because of the ice at the poles will melt. There may be more hurricanes, typhoons and cyclones. A single result could help some people but at the same time be harmful to others. For example fish might shift to new warmer breeding grounds giving fishing boats better catches but others poorer ones. Crops could grow in areas that were once too cold but die off in lands that are now too hot. Questions 1. Why do plants need carbon dioxide? 2. Give some ways that CO 2 is put into the atmosphere. 3. Explain why CO 2 levels are increasing steadily. 4. What would be the surface temperature of the Earth if no CO 2 was present? 5. What is the a) Greenhouse effect and b) Global warming? 6. List ten effects caused by Global warming. 7. Global warming can only be controlled if all the countries of the world agree to do something about it. a) Why is this? b) Some countries produce more CO 2 than others. Name four countries that you think are major producers of greenhouse gases such as CO 2. bill nye melting of ice-caps 32

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