Recognising Chemical Reactions
Aim: When you put substances together, sometimes they react. There is a chemical reaction in each of these experiments. Observe the reactions carefully. By the end of the lesson, you should be an expert at spotting chemical reactions.
Experiment 1
Mix 1 spatulaful of copper carbonate with 10cm3 of either nitric or sulphuric acid in a beaker. Add 25 cm3 of water. Observe what happens.
* How do you know a chemical reaction has happened (at least two points)?
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Experiment 2
Put 20 cm3 of hydrochloric acid into a beaker. Measure its temperature. Add 20cm3 of sodium hydroxide. Stir it. Note the temperature.
Temp. of acid ...... Temp. of mixture at Finish ......
* How do you know a chemical reaction has happened?
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* Is it exothermic or endothermic? ......
Experiment 3
Set up 4 tubes in a rack. Stand the rack on newspaper. Measure 2cm3 of hydrochloric acid into each tube. Put a piece of lead into one tube, a piece of zinc into the second tube, a piece of magnesium into the third tube and very, very carefully, a piece of calcium into the fourth tube.
* Which metals react chemically with the acid?
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* For each metal you have just written down, explain how
you know that a chemical reaction has occurred.
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Experiment 4
Put 25cm3 of ethanoic acid into a beaker. Take the temperature. Add two or three spatulafuls of ammonium carbonate. Take the temperature again.
* How do you know a chemical reaction has happened?
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* Is it exothermic or endothermic? ......
Conclusion
O.K. expert, write down some different ways of how to recognise a chemical reaction!
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