Investigating Elements and Compounds

Aim

To investigate three reactions to learn about elements and compounds.

Apparatus

• Cal-C-Vita tablet

• test tubes

• Bunsen burner

• rubber stopper

• delivery tube

• lime water (a saturated solution of \(\text{Ca}(\text{OH})_{2}\))

• candle

• matches

• copper sulfate (\(\text{CuSO}_{4}·5\text{H}_{2}\text{O}\))

• zinc metal

• hydrochloric acid (\(\text{HCl}\))

Method

Reaction 1

1. Pour clear lime water into a test tube.

2. Into a second test tube place a Cal-C-Vita tablet. Cover the tablet with water and immediately place a stopper and delivery tube into the test tube.

3. Place the other end of the delivery tube into the lime water in the first test tube. Allow it to bubble for 1-2 minutes.

4. Now remove the stopper from the second test tube and hold a lit candle at the mouth of the test tube.

5. Record your observations.

Reaction 2

1. Place a few drops of zinc metal in a test tube and cover the pieces with dilute hydrochloric acid.

2. Record your observations.

3. Now hold a burning match in the mouth of the test tube and observe what happens.

Reaction 3

1. Place a spatula full of copper sulfate crystals into a test tube and heat the tube over a Bunsen burner.

2. Record your observations.

Discussion and conclusion

In the first reaction the lime water goes milky due to the presence of carbon dioxide. (Lime water can be used to detect carbon dioxide gas.) The carbon dioxide gas comes from the sodium bicarbonate (\(\text{NaHCO}_{3}\)) in the tablet. When you hold the candle over the test tube, the carbon dioxide snuffs out the candle flame.

In the second reaction bubbles of hydrogen gas form. Zinc reacts with the hydrochloric acid to form zinc chloride and hydrogen gas.

In the third reaction the copper sulfate crystals go white and droplets of water form on the sides of the test tube. The copper sulfate crystals have lost their water of crystallisation.