Natural Resources — Science STD 9 — Question

Gravitational force is known to exist between all bodies in this universe. Due to existence of gravitational force between the earth and the moon, moon should experience a pull towards the earth and vice versa. Do you expect the orbit of the moon to change due to this force of attraction? Give reason in support of your answer.

What are the three groups into which all the elements can be divided? Name two elements belonging to each group.

Whish of the following diffuses fastest and which the slowest?
Solid, Liquid, Gas
Give reasons for your answer.

What is the specific function of the cardiac muscle?

List any two postulates of Bohr’s model of an atom. 

In a given sample of ammonia, 9g hydrogen and 42g nitrogen are present. In another sample, 5g hydrogen is present along with nitrogen. Calculate the amount of nitrogen in the second sample.

When ice at -10°C is slowly heated, temperature of ice gradually increases till 0°C, the temperature of the system remains constant when the ice change into water and then further rises. Explain the observation.