At the end of this unit you should:

2. At the end of this unit you should: 1. Be able to explain why scientists classify matter into different states. 2. Be able to describe the differences between solids, liquids, gases and plasma (the states of matter). 3. Know the differences between physical changes and chemical changes. 4. Be able to explain the changes involved in freezing, boiling, melting, evaporation and condensation.

3. boiling Brownian Motion chemical change compressed condensation evaporation flow freezing gases Law of Conservation of Mass liquids mass matter particles physical change plasma properties solid state of matter

4. Matter: Anything that takes up space and has mass. Mass: The amount of matter in a substance, given in grams (g) or kilograms (kg). Particle: An extremely small piece of matter.

5. Physical Change: When a substance changes its state, texture, strength or colour, but does not form a new substance. Chemical Change: When two or more substances combine to form a new substance.

6. LIGHTBULB QUESTION • H2O in various states. • A physical not chemical change. • Ice  snow. • Mist and clouds are water vapour (from evaporation of surface of bodies of water and later condensation). • Steam is hot vapour from boiling of all molecules in an amount of water.

7. DEMONSTRATION Demonstration 06.01.01 – Making a cloud in a bottle Equipment: A 2-litre soft drinks bottle – preferably non-contour for greater flexibility, water (tepid works better), a match.

8. DEMONSTRATION Instructions: 1. Pour about 30 ml of warm (tepid) water into a 2 litre soft drinks bottle. Screw on the cap. 2. To saturate the air inside the bottle, shake the bottle vigorously for 30–40 seconds. 3. Unscrew the cap. 4. Light a match and allow it to burn enough to create a significant amount of smoke. 5. Drop it into the bottle, and quickly screw the cap back on the bottle. 6. Do not shake the bottle again at any point. 7. Squeeze the bottle as tightly as possible for five seconds. 8. Release the squeeze in one sharp movement. 9. A cloud will condense in the bottle, which will become denser each time the bottle is squeezed and released.

9. 1. Were the substances that made up the cloud destroyed each time the cloud disappeared? • 2. Were the substances that made up the cloud • created each time the cloud appeared? • In both instances, no, because no new substances are created. Water simply changes state from vapour (gas) to liquid because pressure and temperature both increase and then drop suddenly.

11. Law of Conservation of Mass: Matter can be neither created nor destroyed but is rather converted from one form to another.

12. Investigation 06.01.01: Finding the physical and chemical changes when steel wool is burned Equipment: Using the equipment as shown in Fig. 06.01.03, burn a piece of steel wool.

13. Instructions 1. Cut a strip of aluminium foil that will cover the first 8 cm of one end of the metre stick and wrap it around the metre stick at least four times. This protects the metre stick from scorching. 2. Cut two flaps in the side of the foil cup and bend these around the foil end of the metre stick. This creates a cradle which will hold the steel wool in place. 3. As threads of steel wool can pierce the skin, gloves should be worn when handling it. A scissors can be used to cut suitable pieces from the packaged roll. 4. Cut approximately 4 g of steel wool and place in the foil cup. 5. Place some plasticine/Blu-tac on the other end of the metre stick and balance on the triangular block. 6. The metre stick does not need to be in perfect balance, i.e. level. If imbalanced, a tilt to the Blu-tac end is better.

14. Instructions 7. To stop scorching of the surface beneath, a heat tile should be placed under the steel wool. 8. Using a wooden splint, the steel wool should light easily and remain burning once dry. If it does not light, or burns out before the metal has fully combusted, tease the wool apart to allow more air to pass through it. This is similar to setting kindling for a fire. 9. You should not be too close to the burning steel wool as small sparks containing molten metal can occasionally lift up from the ball of steel wool. 10. After burning, the steel wool should be handled with tongs until cool. 11. Iron oxide coats the steel wool so it cannot be reused, as not enough reactive steel would still be exposed. However, the foil strip and foil cup can be recycled, if desired.

15. 1. You might think that you cannot burn steel with a standard flame. How is it possible to burn steel wool? • It is possible because the steel is in a fine thread mesh and there is a large surface area for reaction. Also because of a low mass in each thread, little heat energy is needed to begin combustion. • 2. To make the steel wool burn, how do you need to arrange it in the foil cup? • The mesh of the steel wool needs to be teased apart to allow sufficient air (oxygen) around each thread for combustion to occur.

16. 3. How much steel wool should you use? Can you use too much or too little? The exact (or a precisely measured) amount of steel wool is irrelevant once there is enough to show a mass change after combustion and cause the metre stick to tilt to the foil cup end.

17. 4. Could you conduct this experiment without using • aluminium foil or the foil cup? • Yes. The steel wool could simply be wrapped around the end of the metre stick, but wrapping can pull the steel wool too tightly together and it will not burn well enough. More importantly, the metre stick will scorch badly or burn. An 8 cm-deep strip of foil wrapping prevents this damage. The foil cup holds the steel wool in place during burning and collects the debris from its combustion.

18. 5. When burning any substance, safety precautions need to be taken. What precautions are needed for this particular investigation? • Goggles, gloves, lab coat and tongs. Care needs to be taken when using scissors.

19. 6. When the steel wool was burned, what physical change took place? Give a reason for your answer. • 7. When the steel wool was burned, what chemical change took place? Give a reason for your answer. • Use the ‘Physical and Chemical Changes’ chart to assess the results of this investigation and draw evidence-based conclusions.

20. 8. Do the results of this investigation agree with the Law of Conservation of Mass? Justify your answer. • Yes, because if matter was destroyed then it could not combine with other substances so iron oxide would not form on the surface of the steel wool and its overall mass would not increase.

21. Property: The particular features of a substance or object that make it similar or different to other substances or objects.

22. Solid: A substance that has a definite shape and volume, cannot be compressed, cannot flow.

23. Liquid: A substance that does not have a definite shape, has a definite volume, can be compressed and can flow.

24. Gas: A substance that does not have a definite shape or volume, can be compressed and can flow.

25. Plasma: A substance that does not have a definite shape or volume, can be compressed and can flow; also conducts electricity.

26. Melting: The change of state from solid to liquid, which happens at the melting point temperature (m.p.). Boiling/Evaporation: The change of state from liquid to gas, which happens at the boiling point temperature (b.p.).

27. Condensation: The change of state from gas to liquid. Freezing: The change of state from liquid to solid.

29. DEMONSTRATION Demonstration 06.01.02 – The three-in-one states of matter Instructions: Your teacher will put 4–5 cm depth of hot water into a jam jar, and then sit a zip-lock bag of ice in the neck of the jar, as per the diagram.

30. DEMONSTRATION Instructions: 1. To prevent too much heat energy being lost to the glass walls of the container, some previously boiled water could be added to the jam jar to a depth of 4–5 cm and left for five minutes. This may be clamped to a retort stand as a precaution against accidental spillage and scalds. 2. Alternatively, the container could have been warmed in a lab oven at approximately 400C, which also means it is safe for handling. 3. Place approximately twelve ice-cubes in a zip-lock bag and seal. 4. Empty the jam jar and refill with boiled water to a depth of 4–5 cm.

31. DEMONSTRATION Instructions: 5. Lay the zip-lock bag across the neck of the jam jar so that it sits just inside the neck without falling into the jar. This will provide a temporary seal. 6. After a few minutes, condensation will appear in the underside of the bag, proving that water vapour (gas) inside the jar has condensed. 7. To show that all three states of H2Oare present, small amount of anhydrous copper sulfate gas can be shaken into the boiled water, ice and onto the condensation to show a colour change. At this point the only explanation needed for the anhydrous copper sulfate is that it changes from white to blue only in the presence of H2O.

32. 1. There are three states of matter present in this demonstration. Explain how this is true. • H2O is the chemical present in each of the substances tested. Ice and boiling water have an obvious difference in temperature. Water vapour (steam) condenses on the outside of the ice-filled zip-lock bag, showing that a change in temperature is enough to effect a change in the state of matter.

33. 2. Did any chemical or physical changes take place during the demonstration? Justify your answer. Condensation on the outside of the zip-lock bag tested the same as the boiled water and ice. This shows that the change from steam to water was physical and not chemical because no new substance was created.

34. Using simple diagrams, explain how a bar of chocolate left on a hot windowsill will melt. • Answers should include: • Bar of chocolate exposed to sunlight from a window • Before and after version • Suitable labels • Brief explanation that the Sun radiates/releases heat and light energy • Chocolate has a low melting point

35. (b) Ice-cubes were added to a glass of orange cordial. After ten minutes ice-cubes had disappeared, a fog had appeared on the outside of the glass and the drink tasted watered-down. Explain how this happened. The temperature of the orange cordial (Kia Ora, Ribena, etc.) was higher than the ice-cubes’ temperature. This caused them to melt as heat moved from the cordial into the ice-cubes causing them to change state. Overall the temperature in the drink and then the glass dropped. This was cool enough to condense the water vapour in the air near the glass, causing droplets to form. As time goes on the droplets will evaporate as the heat energy from the environment warms the glass and the drink.

36. Compression: Forcing the particles of a substance closer together and reducing the amount of space they take up. Kinetic energy: Energy possessed by a body because of its motion.

37. Investigation 06.01.02: Testing the compression of solids, liquids and gases Equipment: Using a disposable syringe, water, a marshmallow and the air in the room, can you suggest how you could show the compression of a solid, a liquid and a gas. You may need to add other equipment to this list.

38. Instructions: 1. Draw out the plunger of an empty, dry 20 ml syringe to its maximum. 2. The extended syringe should be placed between the thumb and index finger of your writing hand (strongest). 3. You should now try to squeeze the plunger home. The plunger should be against the thumb which makes squeezing easier. This should be repeated at least twice. 4. Drawing 15 ml of water into the syringe, the same method should be repeated.

39. Instructions: 5. Using a small amount of Blu-tac, the tip of the 50 ml syringe should be sealed. 6. The plunger should be removed from the barrel of the syringe. A marshmallow should be placed at the bottom of the barrel, and the plunger replaced. 7. Placing the tip of the syringe against a smooth, flat surface, push the plunger home until the marshmallow stops reducing in size. The plunger should then be drawn out until the marshmallow regains its original size.

40. 1. Explain whether the changes you see are physical • or chemical, and why the changes happen. • Compressing air increases internal pressure by forcing molecules closer together. The friction caused by this creates heat energy. The reduction in volume is a physical change, as no new substance is created. • Compressing water results in no change. • Compressing the marshmallow initially compresses the air inside the marshmallow reducing it in volume. This is a physical change. No new substance is formed. But once the air is compressed the marshmallow will not reduce further in volume as it is a solid and incompressible.

41. 2. How might you measure these changes? • The gradations on the syringe can be used to find volume measurement. • 3. Can you explain what might happen if you put a piece of marshmallow into a sealed syringe and push the plunger down? What might happen if you drew the plunger out? • The marshmallow changes volume as the gas within it is compressed and decompressed.

42. Diffusion: The movement of particles in a liquid or gas until the particles are evenly spread throughout the liquid or gas.

43. Investigation 06.01.03: Looking at diffusion in a liquid Equipment : Cold water, boiled water, black ink (or cordial, food colouring etc.), Pasteur pipette, two beakers (or tall drinking glasses, glass or colourless plastic bottles). Instructions: 1. Fill a beaker with 500 ml of tap water. 2. Fill a second beaker with 500 ml of boiled water. 3. Using a Pasteur pipette, add a drop of black ink to each beaker. 4. Note what you observe happening in each beaker.

44. 1. Do your observations prove that diffusion happens? Justify your answer. • If you have waited until the colour of the solute is even throughout the mixture, then diffusion will have been proven.

45. 2. Suggest factors that could speed up or slow down the diffusion in your investigation. Explain your answer. • • Temperature of the solvent (or solute). • • Volume of the solvent (or solute). • • Solvent density – higher density slows diffusion. • • Solute mass – higher mass molecules move more slowly. • • Distance solute must travel through the solvent.

46. 3. Explain how you could test one of these factors in a fair investigation. Remember that you test for one factor while keeping the others fixed. In addition to controlling factors, you need to consider how you will take measurements and ensure the validity of these measurements, e.g. if testing the same volume of solvent at different temperatures by measuring how long diffusion takes, is a mean calculation made from multiple (repeated) trials?

47. DEMONSTRATION Demonstration 06.01.03 – Observing gas diffusion in a tube Diagram

48. DEMONSTRATION Instructions 1. Select two corks (rubber bungs) that will fit the end of the diffusion tube. 2. Clamp the tube securely into the retort stand and place inside an operating fume hut. 3. Take one cotton ball and place over the neck of the concentrated ammonia reagent bottle. Invert the bottle several times until the cotton ball is soaked. 4. Place the cotton ball in one end of the tube and stopper this end. 5. Repeat this procedure with hydrochloric acid. 6. The mounted diffusion tube may now be removed from the fume hut and placed where students will be able to see it clearly (against a dark background is preferable). 7. As a precaution even when using a fume hut, ensure that the lab is well-ventilated.

49. DEMONSTRATION Instructions 8. The diffusion tube should only be dismantled in an operating fume hut. The cotton balls should be thoroughly rinsed with water before disposal. 9. The diffusion tube and corks should be cleaned with hot, soapy water to prevent a build-up of ammonium chloride reside. These should be suitable for re-use if cared for.

50. 1. What change do you observe happening at position X? • A white, smoky ring or cloud should appear. • 2. What has happened to the substances soaked onto the cotton wool that allows this change to happen? • Both liquids have evaporated.