Improvement in Food Resources — Science STD 9 — Question

There are four substances W, X, Y and Z. The substance W is a dark violet solid having diatomic molecules. A solution of W in alcohol is used as a common antiseptic C. The substance X is a white solid which is usually recovered from sea water on a large scale. The substance Y is a white solid which is insoluble in water and used in the form of small balls for the safe storage of woollen clothes. The substance Z is a yet another white solid which is used in making commonly used dry cells.

1. Name (i) W (ii) X (iii) Y and (iv) Z.
2. Out of W, X, Y and Z, which substance/ substances can undergo sublimation?
3. Which substances organic in nature?
4. What is the name of substance C?
5. Which substance belongs to the halogen family?

The graph given alongside shows how the speed of a car changes with time:

1. What is the initial speed of the car?
2. What is the maximum speed attained by the car?
3. Which part of the graph shows zero acceleration
4. Which part of the graph shows varying retardation?
5. Find the distance travelled in first 8 hours.

Explain the mechanism of compost formation.

What is lymph? Describe its function.

What are diploid and haploid number?

Discuss the various methods which are used to control plant diseases.

How can reverberations in a big hall or auditotium be reduced?`

If the back of your hand is moistened with alcohol, you will find that it rapidly becomes dry. Why is it that while it is drying, your hand feels cool?

How can you obtain pure water from a salt-water mixture (or salt-solution)? Draw a meat and labelled diagram of the apparatus you would use to obtain pure water from a salt-water mixture (or salt-solution).