PHYSICS [1 Mark Question Answer]

Substances that catch fire easily are called inflammable substances. On the other hand, substances that do no catch fire easily are called nonflammable substances.

Heat energy always flows from a body at higher temperature to a body at lower temperature, when brought in contact.

Convection is the process of transfer of heat in fluids (liquids and gases) wherein the molecules actually move from one part of the fluid to the other.

Conduction is the process of transfer of heat energy in solids, from one particle to another, without the actual movement of the particles.

The change of a substance from its liquid state to its gaseous state at any temperature below its boiling point is called evaporation.

The process by which certain substances which are solid directly changes into vapours, without changing into liquid state.

The process during which a liquid changes to solid state at a constant temperature by release of heat energy.

The process during which a substance in its vapour or gaseous state changes into its liquid state at a constant temperature by release of heat.

The process during which a liquid changes to vapour state at a constant temperature by absorption of heat.

The process during which a solid changes to a liquid state at a constant temperature by absorption of heat.

Condensation.

Condensation.

Freezing.

Process A takes place at 0 °C while process B takes place at 100 °C.

Process A : Melting
Process B : Boiling

Wood, kerosene oil and petrol are used as fuels because they are inflammable substances that bum easily and release a lot of heat and energy.

Water is easily available everywhere and helps in extinguishing fire as it cuts off oxygen supply to the fire and stops combustion.

Asbestos is used in fire-proofing buildings because it is a non-flammable material and does not catch fire.

As molecules in solids are tightly packed, actual movement of molecules is not possible in solids. Hence, convection does not take place in solids. So, heat transfer by convection takes place only in fluids, that is, in liquids and gases.