Matter in Our Surroundings — Science STD 9 — Question

Two balls of the same size but of different materials, rubber and iron are kept on the smooth floor of a moving train. The brakes are applied suddenly to stop the train. Will the balls start rolling? If, so in which direction? Will they move with the same speed? Give reasons for your answer.

Why does a ship made of iron and steel float in water whereas a small piece of iron sinks in it?

The substance X normally exists in a physical state which can flow easily but does not fill its vessel completely. It also turns anhydrous copper sulphate blue. When substance X is cooled excessively, it changes into a substance Y which has a fixed shape as well as a fixed volume. If, however, the substance X is heated strongly, it changes into a substance Z which has neither a fixed shape nor a fixed volume.

1. Name the substances (i) X (ii) Y and (iii) Z.
2. What is the process of conversion of X into Y known as?
3. At which temperature X gets converted into Y?
4. What is the process of conversion of X into Z known as?
5. At which temperature X gets converted into Z?

Draw a velocity versus time graph of a stone thrown vertically upwards and then coming downwards after attaining the maximum height.

How will you separate iron pins from sand?

Explain why, we can easily move our hand in air but to do the same through a plank of wood, we need a karate expert.

In which tissue is found anyone of the following Structures: neuron, dendrite, cilia, collagen fibres, elastin fibre.

Define gravitational constant. What are the units of gravitational constant?

Why do we hear more clearly in a room with curtains then a room withour curtains?