The Fundamental Unit of Life — Science STD 9 — Question

Calculate the mole ratio of 240g calcium and 240g of magnesium.
(Ca = 40u; Mg = 24u)

A bulb lights up when connected to a battery. State the energy change which takes place:

1. In the battery.
2. In the bulb.

On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.

Does the solubility of a substance change with temperature? Explain with the help of an example.

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 water is cooled to a temperature x, it gets converted into ice at temperature x by a process called P. And when ice at temperature x is warmed, it gets reconverted into water at the same temperature x in a process called Q.

1. What is the value of temperature x in Kelvin?
2. What is the process P known as?
3. What is the name of energy released during process P?
4. What is the process Q known as?
5. What is the name of energy absorbed during process Q?

A moving bicycle comes to rest after sometime if we stop pedalling it. But Newton’s first law of motion says that a moving body should continue to move for ever, unless some external force acts on it. How do you explain the bicycle case?

A ball is thrown vertically upwards with a velocity of 49m/ s. Calculate

1. The maximum height to which it rises
2. The total time it takes to return to the surface of the earth.

Define:

1. Solute
2. Solvent

Calculate the momentum of the following:

1. An elephant of mass 2000kg moving at 5m/s.
2. A bullet of mass 0.02kg moving at 400m/s.