Phases Change and heat transfer

Phase changes

refers to the transition of matter from one phase to another due to loss or gain of heat

Two types of phase changes

Endothermic & Exothermic

Endothermic

reactions occur because of heat absorbtion

Example of Endothermic reactions:

Fusion, Vaporisation & Sublimation

exothermic reaction

A reaction that releases energy in the form of heat

Example of Exothermic reaction:

Freezing, condensation, deposition

Latent heat

also known as hidden heat, the amount of energy given out or absorbed when a substance changes phase while the temperature remains constact

Latent heat of Fusion

The amount of energy required to change a unit mass of a substance from solid to liquid with constant temperature

latent heat of Fusion of water

3.34 x 10⁵ J/kg

Latent heat of Fusion formula:

Lf = J/g

latent heat of freezing

heat released when water freezes; the reverse of latent heat of fusion

latent heat of vaporization

an energy absorbed to change water into steam without change in temperature

Vaporisation

mean changing water into vapor

Latent heat of Vaporisation of water

22.6 x 10⁵ J/kg

Condensation

the reverse process where steam turns into liquid water. Here heat is removed from steam at 100°C while maintaining the temperature

Solid - liquid change of state

Freezing and Melting

Solidification/Freezing

the change of state from liquid to solid

freezing point

the temperature at which a liquid becomes a solid

Fusion/Melting

Changing a solid to the liquid state by heating.

melting point

the temperature at which a substance changes from a solid to a liquid

Liquid - Gas Changes of state

Vaporisation & Condensation

Vaporisation

The change of state from a liquid to a gas

Vaporisation occurs in two ways:

Evaporation & boiling

Evaporation

this happens when Vaporisation takes place at the surface of a liquid

Boiling

vaporization that occurs on and below the surface of a liquid

Boiling point

the temperature at which a substance changes from a liquid to a gas

Condensation

the change from the gaseous to the liquid state of matter

condensation point

the temperature where condensation takes place

Solid - Gas changes of state

Sublimation & Deposition

Sublimation

the conversion of a solid directly to a gas without passing through the liquid state

Deposition

reverse process of sublimation, which transforms gas into solid

Heat

is described as the quantity of Thermal energy absorbed or given off by a body

Principles of calorimetry

states that the insulated system, heat energy lost by the hot body is equal to the heat energy gained by the cold body

Principle of calorimetry formula:

Q = mC∆T

Heat transfer

occurs when thermal energy moves from one place to another due to difference of temperature

Three ways of heat transfer

conduction, convection, radiation

Conduction

The direct transfer of heat from one substance to another substance that it is touching.

Convection

The transfer of heat by the movement of a fluid

Radiation

Energy that is radiated or transmitted in the form of rays or waves or particles.