In an experiment, four nails 1, 2, 3 and 4 are fixed with candle wax onto a metal bar and one end of bar is heated by means of boiling water as shown in the diagram below

A, B, C and D are thermometers inserted in holes along the bar to measure the temperatures at the various points

1. What is the temperature of the boiling water?

2. State the observations that will be made about nails 1, 2, 3, and 4.

3. State the observations that will be made about the temperatures recorded by thermometers A, B, C, and D.

4. What mode of heat transfer is demonstrated in the experiment?

5. State one effect of heat that is associated with the experiment.

6. State the aim of the experiment.

In an experiment, a student took three iron nails and cleaned their surfaces dry and placed them in three separate test tubes in set-ups A, B and C as shown in the diagram. After three days the nail in set-up A was found to have rusted while the nails in set-ups B and C did not.

Answer the following questions

1. Why was the water in set-up B boiled?

2. Explain the function of the oil on top of the water in set-up B.

3. State the purpose of the rubber stopper in set-up C.

4. Why did the nail in set-up A rust?

5. Suggest an aim for the experiment.

6. From the experiment, explain why oil or grease is applied on the surface of a metal to prevent rusting.

In an experiment, the following activities were carried out on two green leaves A and B. Leaf A was from a plant placed in the sunlight for sometime while leaf B was from a plant placed in a dark cupboard for 24 hours.

Activity
I. Leaves dipped in boiling water for 1 minute
II. Leaves dipped in warm alcohol
III. Leaves washed in cold water
IV. Leaves dipped into iodine solution

1. Explain why each of the activities I, II, III, and IV was carried out.

2. State the colour change of leaf A.

3. Explain why leaf A changed colour but leaf B did not.

4. Suggest an aim for the experiment.