Week 10: Year 8 Chemistry Revision

1. Week 10: Year 8 Chemistry Revision Lesson 1 Gas Tests

2. Gas Tests WALT: State how to test for a variety of gases and practise our practical skills • I must be able to list three gas tests • I should be able to correctly collect gases using a water bath and test tube • I could correctly answer several questions on gas tests

3. Today there are 5 stations set up around the room Your task is to carry out the tasks set for you at each station You are going to test for several gases You must spend no longer than 8 minutes at each station

4. Safety Point • Suck-back When heating a liquid, if you take away or turn off the heat and leave the delivery tube in the water bath or other cold liquid, it will suck the cold water back up its tube. When this reaches the hot part of the tube, it could shatter Therefore, if you take away the heat, remove the delivery tube from the water bath immediately!

5. 1. Limewater test for……? • Using a fresh straw, blow into the limewater • What does this prove? SAFETY: Do not suck on the straw! Throw the straw away when you are finished! • Write out the respiration equation • Where do we get the glucose from that we need for this reaction? • What equation in science is the opposite to respiration? How can this help us reduce the effects of pollution?

6. 2. Heating potassium permanganate • Collect the gas in a test tube • Test the gas with a lit splint BE CAREFUL OF SUCK-BACK!! Write down: • A sentence describing what happens when potassium permanganate is heated (which gas was given off and how you know) • Why suck-back can be dangerous and how you avoid it

7. 3. Reacting HCl and magnesium • Place 10cm3 of hydrochloric acid in a conical flask and add a 1cm long strip of magnesium • Collect the gas in a test tube by bubbling it through a water bath (see p.184 of Riley ISEB book if you need help on this) • Test the gas with a lit splint Write down: • A sentence describing what happens when HCl and Mg are put together (which gas was given off and how you know) • What signs tell you that a chemical reaction has taken place?

8. 4. Reacting HCl and marble chips (calcium carbonate) • Place 2cm of hydrochloric acid in a boiling tube and add a spatula of marble chips • Collect the gas in a test tube by bubbling it through a water bath • Test the gas with a lit splint Write down: • A sentence describing what happens when HCl and CaCO3 are put together (which gas was given off and how you know) • Why might this gas be useful in fire extinguishers? • See if you can write a word equation for the reaction

9. 5. Acid Rain and Coral Reefs The hard coral in oceans is made from the same substance as marble chips – calcium carbonate (CaCO3). Acid rain from pollution in the air is dissolving in our oceans. • Why is this becoming an increasing problem for ocean coral? (if you haven’t done Station 4, use P. 149 of the green ISEB Riley book to help you) • Which gases contribute the most to acid rain? Think of an experiment you have done that produces one of these gases. Use the text book to jog your memory.

10. Plenary • Write a quick table out with the tests for each gas • What were your question answers? Swap books and we’ll go through the answers.

11. Prep • Choose one of the experiments we did today and write it up as a proper practical – diagram, method, result, conclusion