FORM 4: 4.6 FORMULA

SPECIFIC HEAT CAPACITY, c

SPECIFIC LATENT HEAT, l

BOYLE’S LAW

CHARLES’ LAW

PRESSURE LAW

FORM 4: 4.5 MEANINGS

ITEM	MEANING
THERMAL EQUILIBRIUM	Thermal equilibrium between two objects is a condition where both objects have the same temperature and there is no net flow of heat between the two objects.
HEAT CAPACITY	The heat capacity of a body is the amount of heat that must be supplied to the body to increase its temperature by 1 oC.
SPECIFIC HEAT CAPACITY	The specific heat capacity of a substance is the amount of heat that must be supplied to the increase the temperature by 1 oC for a mass of 1 kg of the substance.
LATENT HEAT	Latent heat is the heat absorbed or the heat released at constant temperature during a change of phase.
LATENT HEAT OF FUSION	Latent heat of fusion is the heat absorbed by a melting solid.
LATENT HEAT OF VAPORISATION	Latent heat of vaporisation is the heat absorbed during boiling.
SPECIFIC LATENT HEAT	The specific latent heat of a substance, l is the amount of heat required to change the phase of 1 kg of the substance at a constant temperature.
SPECIFIC LATENT HEAT OF FUSION	The specific latent heat of fusion of a substance is defined as the amount of heat required to change 1 kg of the substance from solid to liquid phase without a change in temperature.
SPECIFIC LATENT HEAT OF VAPORISATION	The specific latent heat of vaporisation of a substance is defined as the amount of heat required to change 1 kg of the substance from liquid to gaseous phase without a change in temperature.
BOYLE’S LAW	Boyle’s law states that for a fixed mass of gas, the pressure of the gas is inversely proportional to its volume when the temperature is kept constant.
CHARLES’ LAW	Charles’ law states that for a fixed mass of gas, the volume of the gas is directly proportional to its absolute temperature when its pressure is kept constant.
PRESSURE LAW	Pressure law states that for a fixed mass of gas, the pressure of the gas is directly proportional to its absolute temperature when its volume is kept constant.
ABSOLUTE ZERO OF TEMPERATURE	The absolute zero of temperature is the lowest possible temperature which is – 273 oC.

FORM 4: 4.4 UNDERSTANDING THE GAS LAWS

PROPERTY OF GAS: VOLUME

§          The molecules move freely in random motion and fill up the whole space in the container.

§          The volume of the gas is equal to the volume of container.

PROPERTY OF GAS: TEMPERATURE

§          The molecules are in continuous random motion and have an average kinetic energy which is proportional to the temperature.

PROPERTY OF GAS: GAS PRESSURE

§          The molecules are in continuous random motion.

§          When a molecule collides with a wall of the container and bounces back, there is a change in momentum and a force is exerted on the wall.

§          The force per unit area is the pressure of the gas.

BOYLE’S LAW

    Boyle’s law states that for a fixed mass of gas, the pressure of the gas is inversely proportional to its volume when the temperature is kept constant.

ABSOLUTE ZERO OF TEMPERATURE

The absolute zero of temperature is the lowest possible temperature which is – 273 ^oC.

CHARLES’ LAW

    Charles’ law states that for a fixed mass of gas, the volume of the gas is directly proportional to its absolute temperature when its pressure is kept constant.

PRESSURE LAW

    Pressure law states that for a fixed mass of gas, the pressure of the gas is directly proportional to its absolute temperature when its volume is kept constant.

FORM 4: 4.3 UNDERSTANDING SPECIFIC LATENT HEAT

LATENT HEAT

Latent heat is the heat absorbed or the heat released at constant temperature during a change of phase.

The latent heat absorbed is used to break up the bonds between the particles.

LATENT HEAT OF FUSION

Latent heat of fusion is the heat absorbed by a melting solid.

LATENT HEAT OF VAPORISATION

Latent heat of vaporisation is the heat absorbed during boiling.

SPECIFIC LATENT HEAT, l

The specific latent heat of a substance, l is the amount of heat required to change the phase of 1 kg of the substance at a constant temperature.

SPECIFIC LATENT HEAT OF FUSION

The specific latent heat of fusion of a substance is defined as the amount of heat required to change 1 kg of the substance from solid to liquid phase without a change in temperature.

SPECIFIC LATENT HEAT OF VAPORISATION

The specific latent heat of vaporisation of a substance is defined as the amount of heat required to change 1 kg of the substance from liquid to gaseous phase without a change in temperature.

HEATING CURVE

Part	Change in temperature	Phase
AB	increase	solid
BC	unchanged	solid and liquid
CD	increase	liquid
DE	unchanged	liquid and gas

COOLING CURVE

Part	Change in temperature	Phase
PQ	decrease	gas
QR	unchanged	gas and liquid
RS	decrease	liquid
ST	unchanged	liquid and solid

FORM 4: 4.2 UNDERSTANDING SPECIFIC HEAT CAPACITY

HEAT CAPACITY

The heat capacity of a body is the amount of heat that must be supplied to the body to increase its temperature by 1 ^oC.

SPECIFIC HEAT CAPACITY, c

The specific heat capacity of a substance is the amount of heat that must be supplied to the increase the temperature by 1 ^oC for a mass of 1 kg of the substance.

APPLICATIONS OF SPECIFIC HEAT CAPACITY

COOKING POT

§   Copper has a smaller specific heat capacity.

§   Therefore, the copper base heats up very quickly.

§   The handle is made of a material which has a larger specific heat capacity.

§   Therefore, it will not become too hot even if heat is absorbed.

THE COOLING SYSTEM OF A CAR ENGINE

§         Water which has a high specific heat capacity is suitable to use as cooling agent in car radiator as it can absorb a large quantity of heat with little increase in temperature.

FORM 4: 4.1 UNDERSTANDING THERMAL EQUILIBRIUM

A HOT AND A COLD OBJECT IN THERMAL CONTACT

1.       Energy is transferred between the objects.

2.       Energy is transferred at a faster rate from the hotter object to the colder object.

3.       Energy is also transferred from the colder object to the hotter one, but at a slower rate.

4.       Thus, there is a net flow of energy from the hotter object to the colder object.

THERMAL EQUILIBRIUM

1.       After a while, the two objects have the same temperature.

2.       Energy is transferred at the same rate between the two objects.

3.       Thus, there is no net heat transfer between the objects.

4.       The two objects are said to be in thermal equilibrium.

THE MEANING OF THERMAL EQUILIBRIUM

Thermal equilibrium between two objects is a condition where both objects have the same temperature and there is no net flow of heat between the two objects.

LIQUID-IN-GLASS THERMOMETER

DESIGN OF LIQUID-IN-GLASS THERMOMETER

CHARACTERISTICS	EXPLANATION
a glass bulb with thinner wall	heat can be transferred to the mercury faster
narrower capillary tube	increase the sensitivity of the thermometer by producing a longer mercury column
wall of capillary tube is made of glass	glass is a good insulator
mercury is used	§  expands and contracts rapidly and uniformly §  does not stick to the glass wall of capillary tube §  opaque and can be easily seen