09. Acid attack

What factors affect how a metal reacts with an acid?

Apparatus

• • boiling tube

  • test tube rack

  • measuring cylinder (10 or 25 cm³)

  • stopclock

  • thermometer

  • piece of magnesium (1 cm long)

  • dilute hydrochloric acid

  • eye protection

Method

A Measure out 5 cm³ of hydrochloric acid and pour it into the boiling tube.

B Measure the temperature of the acid and write it down.

C Take the piece of magnesium. Drop it in the boiling tube and start timing.

D Watch what happens to the magnesium and the acid.

E When the reaction is finished, stop the clock. Note the time.

F Measure the temperature of the liquid in the tube.

Recording results

G Record your results in a suitable table.

H Calculate the temperature change.

Considering your results / conclusions

1 Write a word equation for the reaction that took place.

2 How could you tell:

a that a reaction was taking place?

b when the reaction had finished?

3 Why do you think the reaction finished? Use the evidence from the observations to explain what has been used up in the reaction.

4 How could you do a simple experiment to test your ideas? Think about how you might use another piece of magnesium or universal indicator solution. What results would you predict from this experiment?

Can you...

> make careful observations

> think up theories to explain observations

> explain how ideas lead to new predictions