Question 55
A new iron nail is placed in each of four test tubes, as in the diagram.
Test tube 1 contains nothing, apart from the nail, and is open to the air.
Test tube 2 contains water and the nail is half in the water. The tube is open to the air. So, this tube has air and water.
Test tube 3 has calcium chloride in the bottom. The calcium chloride absorbs water so the air inside the tube is dry. The tube is stoppered.
Test tube 4 has water that has been boiled to remove as much dissolved gas as possible. On top of the boiled water is a layer of oil. This stops any air entering the water. The tube is stoppered.
| Tube number | Contains | Result |
|---|---|---|
| 1 | moist air | nail is rusted |
| 2 | water and air | nail is very rusty |
| 3 | dry air | no rust |
| 4 | boiled water covered with oil, no air | small amount of rust |
Why is the same type of nail used in all test tubes?
Test tube 1 contains nothing, apart from the nail, and is open to the air.
Test tube 2 contains water and the nail is half in the water. The tube is open to the air. So, this tube has air and water.
Test tube 3 has calcium chloride in the bottom. The calcium chloride absorbs water so the air inside the tube is dry. The tube is stoppered.
Test tube 4 has water that has been boiled to remove as much dissolved gas as possible. On top of the boiled water is a layer of oil. This stops any air entering the water. The tube is stoppered.
| Tube number | Contains | Result |
|---|---|---|
| 1 | moist air | nail is rusted |
| 2 | water and air | nail is very rusty |
| 3 | dry air | no rust |
| 4 | boiled water covered with oil, no air | small amount of rust |
Why is the same type of nail used in all test tubes?
