While performing an experiment, a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.

i. Define electromagnetic induction.

ii. Two coils P and S are wound over the same iron core. Coil P is connected to battery and key and the coil S is connected to galvanometer. Draw a suitable diagram of this arrangement and write your observations when:

A. Current in the coil P is started by closing the key.

B. Current continues to flow in coil P.

C. Current in coil P is stopped by removing the key.

Explain the reason for such observations.

OR

Briefly explain an activity to plot the magnetic field lines around a bar magnet. Sketch the field pattern for the same specifying field directions.

A region A has magnetic field lines relatively closer than another region B. Which region has stronger magnetic field. Give reason to support your answer.

i. What is ‘Chipko Movement’? Why should we conserve forests?

ii. Suggest any four changes that you would like to be incorporated in the life-style of students of your age to move towards a sustainable use of available resources.

iii. An environmentalist on visit to your school suggested the use of three R’s to save the environment. Explain what he meant by three R’s and how you would follow his advice at home.

A student is studying the properties of acetic acid in his school laboratory. List two physical and two chemical properties which he must observe and note in his record book.

Two physical and two chemical properties that must be observed and noted are:

The following experiment was set-up to show that a gas is given out during respiration. But there was no rise in the level of water. Why did it happen?