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Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
Chemical reactions, physical and chemical changes
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Chemical reactions, physical and chemical changes

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  • 1. Chemical Reactions A stick of TNT explosive contains chemicals. When it blows up a lot of heat is given out with large volumes of gasses and a flash of light. All that is left is some ash. It is impossible to collect all the products and turn them back into a stick of TNT. When chemicals react to form completely new substances we call this a chemical change. (examples baking a cake, toasting bread, boiling potatoes) Other changes that occur when solids turn into liquids or liquids become gasses are called physical changes. Physical changes can be easily reversed. (examples water freezing, water boiling) Watch the video of sodium burning in chlorine gas. Is this a physical or chemical change and why? This might help you. Physical changes Chemical changes *Not much heat involved *Lots of heat *Easy to change back *Can’t change back Eg. Melting, freezing, boiling *sometimes lots of light given out Follow the instructions carefully and decide whether the change you are observing is a physical change or a chemical change.
  • 2. Experiment 1 (Wear eye protection) 1. Pour some dilute sulphuric acid into one of the big test tubes, about one third of the way up. 2. Add three zinc lumps. 3. Place the other test tube over the top of the first one to catch any gas that is given off. 4. Once you have collected what is given off for a few minutes Take the top test tube away and put a lit match under it ( don’t turn the test tube upside down as any gas you collect will escape) 5. Empty the test tube into the residues beaker on the bench. What did you see happening? Make as many observations as possible in the space underneath. Was this a physical change or a chemical change?
  • 3. Experiment 2 (Wear eye protection) There are two beakers on the laboratory bench. One beaker contains a solution of lead nitrate (POISON). The other beaker contains a solution of potassium iodide (POISON) There is a dropping pipette in each beaker. DON’T mix them up. 1. Put about half a pipette of one solution into your test tube. Replace the pipette 2. Use the pipette in the other beaker to put the same amount of the second solution into your test tube.Replace the pipette. What happened? 3. Rinse your test tube out thoroughly and repeat if you want. 4. Rinse your test tube out thoroughly for the next group (I will know immediately if you mix up the solutions or the pipettes!!) Describe what happens. Was this a physical change or a chemical change?
  • 4. Experiment 3 (Wear eye protection) You have a beaker with blue copper sulphate solution (POISON) and a bottle with dilute ammonia solution (Poison). 1. Pour copper sulphate solution into your test tube. 2. Pour some ammonia solution into the test tube a few drops at a time slowly. What happens? 3. Keep adding the ammonia solution until there are no further changes. What happens? 4. Rinse out your test tube thoroughly for the next group Write down as many observations as possible Was this a physical change or a chemical change?
  • 5. Experiment 4. (Wear eye protection) You have a bottle with copper carbonate on the bench. 1. Put a teaspoon of copper carbonate (Poison) in the test tube. 2. Heat the test tube with the copper carbonate in the hot part of a Bunsen flame (The tip) 3. What changes do you see happening? 4. When you finish, empty any solid from the test tube into the residues beaker. Record as many observations as possible in the space below.
  • 6. Experiment 5 (Wear eye protection) Take a piece of magnesium strip. What does it look like? Hold it tightly in the metal tongs and place it in the Bunsen flame What happens next? What does the magnesium look like when it has finished reacting? Write down all your observations below. Was this a physical change or a chemical change?
  • 7. Experiment 6. (Wear eye protection) You have some copper carbonate (POISON) on a piece of paper. There is also a bottle of dilute sulphuric acid. There are also some wooden splints. 1. About one third fill the large test tube with the acid. 2. Use the wooden splint to put a small amount of copper Carbonate into the acid in the test tube. 3. What happens? 4. Add another small amount. 5. What happens? 6. Keep adding small amounts of the carbonate until the changes appear to stop 7. Pour the contents of the test tube into the residues beaker when you have finished. Write down all you observations. Was this a physical change or a chemical change?
  • 8. Experiment 7 Heating iodine Teacher demonstration. What did you see happening? Was this a physical change or a chemical change. Experiment 8 Heating sulphur in a test tube. A teacher demonstration. What did you see happening? Was this a physical change or a chemical change?

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