Pakistan MCQs

Heating usually increases particle motion and separation.
This commonly causes thermal expansion.

Metal structures expand in hot weather.
Gaps prevent buckling and structural damage.

Melting occurs when a solid gains enough energy to become liquid.
It happens at the melting point under fixed pressure.

Freezing removes energy from a liquid until it forms a solid.
For pure water at standard pressure, this occurs at 0°C.

Evaporation occurs at the surface of a liquid.
Higher temperature and moving air usually increase its rate.

Condensation occurs when gas particles lose energy.
Water vapor condenses into droplets on a cool surface.

The highest-energy water molecules escape during evaporation.
This lowers the average energy and temperature of the skin.

Pressure is measured in pascals.
One pascal equals one newton per square metre.

Temperature indicates how energetic particle motion is on average.
It determines the direction of heat flow.

Pascal's law states that pressure applied to a confined fluid is transmitted equally.
This allows force multiplication in hydraulic brakes.

Spontaneous heat transfer occurs from higher to lower temperature.
It continues until thermal equilibrium is approached.

Water exerts an upward buoyant force on immersed objects.
Floating occurs when this force balances the object's weight.