Yeast is used in the production of

Rayon is different from synthetic fibres because:

Purest form of carbon is

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to

Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement.

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

When electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates

The presence of a small amount of impurities makes water

The like charges

When a glass rod is rubbed with a piece of silk cloth, the rod

Which is biodegradable? Paper bag or polythene bag?

Define cellulose.

What are natural fibres?

What are artificial fibres?

How is rayon formed?

Name any two thermoplastic and thermosetting plastics.

Name the material that is used to make ropes for rock climbing.

Why is Terylene popular polyester?

Name the articles made from PET.

What is the versatility about melamine?

Keenrose is a fuel used in jet crafts.

Name two contact forces.

Name the force that always opposes the applied force.

Give two examples of good conductors.

What is static electricity?

Give the term used for spherical bacteria.

Why are vaccines so important for children?

Write the name of raw materials which are used in making nylon.

Why is nylon used for making parachutes and ropes for rock climbing?

Where coal is found in India?

Write different uses of coal-tar.

It is dangerous to touch an electrical appliance with wet hands. Explain why

Sometimes we see that the liquid is conducting but the bulb may not glow. Why?

Mention the name of the natural phenomena which can be predicted to some extent.

What is an earthquake? What happens when it occurs?

What are the major groups of microorganisms?

How plastics are used in health care industry?

What are the advantages of using CNG and LPG as fuels?

Mention three examples that show that friction produces heat.

The strips of an electroscope diverge when a charged body is brought in contact with the metal clip. Now the clip is touched gently by our hand. What will happen to the strips? Explain.

How can we prevent the following diseases?
(a) Cholera (b) Typhoid (c) Hepatitis-A

Despite being very useful, it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?

We say fossil fuels will last only for a few hundred years. Comment.

It is much easier to burst an inflated balloon with a needle than by a finger. Explain.

Across:
1. The substances that reduce friction.
2. Friction when we try to move an object at rest
3. Apply a force to overcome.
Down:
4. Axles of bicycles.
5. The frictional force exerted by fluids is called.
6. Body rolls over the surface of another body.

Observe the circuit given in figure.

Boojho set up this circuit for purification of copper. What will be the nature of
(a) plate A
(b) plate B
(c) and the solution. Explain the process of purification

Explain why it is safer to use a wireless telephone instead of a land line telephone during lightning.

Across:
1. The graph used to record seismic waves.
2. The scale used to measure the magnitude of earthquake.
3. Sudden movement in the Earth plates.
4. A method of charging a neutral material.