Rate of Evaporation

1. Evaporation is the process of converting a substance (such as water) from its liquid state to its gaseous state at temperature lower than the boiling point of the liquid.
2. There are several ways of making a liquid evaporate faster:
1. Increase its temperature 
2. Increase its surface area 
3. Pass air through it or across its surface 
4. Make the liquid into a fine spray
   A spray is made up of millions of tiny liquid droplets with a very large total surface area. The highly curved surfaces make it easier for molecules to escape.

Measuring the Specific Latent Heat of Vaporization of Water

1. Figure above shows the apparatus used. When the water in the can is boiling vigorously, the mass reading on the balance is noted and a stopwatch started. A few minutes later, the stopwatch is stopped and the mass reading is taken again.
2. The difference in the mass readings gives the mass of water which has been changed into steam during the time measured.
   Therefore, the specific latent heat of vaporisation of water can be calculated by the following equation
   
   

1. The boiling point of a liquid is proportional to the air pressure of the surrounding. The higher the air pressure, the higher the boiling point.
2. At higher altitude, the atmospheric pressure is lower. Therefore the boiling point of a liquid will decrease at higher altitude.

Pressure Cooker

1. Pressure cooker can cook faster than normal cooker.
2. The high gas pressure inside the pressure cooker increases the boiling point of the liquid in the pressure cooker.
3. As a result, the food is cooked under higher temperature. More heat is supplied to the food, hence make cooking faster.
4. The function of the safety valve is to release extra steam to the surrounding and consequently reduce the pressure in the pressure cooker when it is too high.

Measuring the Specific Latent Heat of Fusing of Ice

1. Figure above shows the apparatus setup to determine the specific latent heat of fusion of ice. Some ice at 0 °C is heated by a small electric heater which is left switched on for several minutes. 
2. Some of the ice melts to form water which runs down through the funnel and is collected in the beaker. 
3. The mass of ice (m) melted is found by measuring the mass of water collected.
4. If the power of the heater is P and the time taken to heat the ice = t, then the thermal energy supplied by the heater = thermal energy used to melt ice = Pt.
   Therefore, the specific latent heat of fusion of ice
   
5. 

Precaution Steps:

1. The heating element of the heater must fully immerse in ice so that all the heat generated is absorbed by the ice.
2. A control set is needed to estimate the amount of mass of ice melted by the heat from the surrounding.

Note:

1. The heat received by ice is less than the calculated value Pt as some heat is lost to the surrounding. This will result in the value of l obtained from the calculation to be slightly higher than the standard value.
2. If impurity is present in water, the melting point of the water will be lower than normal.

Figure below shows the change of the temperature when a gas is cooled to become solid.

Figure below shows the change of the temperature when a solid is heated until it become gas.

1. Temperature remain unchanged because the heat absorbed is used to overcome the force between the particles in the solid.
2. The heat absorbed to change a solid to liquid is called the latent heat of fusion.

1. Temperature remain unchanged because the heat absorbed is used to overcome the force between the particles in the liquid and also the atmospheric pressure.
2. The heat absorbed to change a liquid to gas is called the latent heat of vaporisation.
   
   

1. When a solid melt, heat is absorbed but the temperature remains constant.
2. When a liquid is boiling, heat is also absorbed but the temperature again remains constant.
3. The heat absorbed or given out at constant temperature during the change of phase is known as latent heat.
4. The heat energy that releases during condensation or boiling is called the latent heat of vaporization.
5. The heat energy that releases during freezing or melting is called the latent heat of fusion.

Cooking Pot

1. Different part of a cooking pot are made up of different material.
2. The base of a cooking pot is usually made up of copper because
   1. copper has low specific heat capacity so that it need less heat to raise up the temperature.
   2. copper is a good heat conductor.
   3. copper has high density. The heavier base can make the pot become more stable. 
3. The handles of cooking pot is usually made up of plastic or wood because
   1. plastic and wood have high specific heat capacity. Their temperature won’t become too high even it absorbs large amount of heat.
   2. plastic and wood are good heat insulator.
   3. plastic and wood have low density hence they do not add much to the total weight of the pot.
4. The body of the cooking pot is usually made up of stainless steel because
   1. steel has low specific heat capacity and hence need need less heat to raise up the temperature.
   2. steel does not react chemically with the food.

Car Engine

1. Water is used to cool down the car engine.
2. Water is used as the cooling agent in the car cooling system because 
   1. it has high specific heat capacity. It can absorb a large amount of heat without a high increase in temperature.
   2. it is cheap and can be obtained easily.
3. Water is pumped through the channels in the engine block to absorb heat.
4. The hot water flows to the radiator and is cooled by the air flows through the fins of the radiator.
5. The cool water flows back to the engine again to capture more heat and this cycle is repeated continuously.

Applications of Specific Heat Capacity - Factories with Low Ceiling

1. Some factories without large machinery are constructed with low ceilings to reduce the volume of air inside the building. 
2. The smaller mass of air will have a smaller heat capacity.
3. As a result, less heat needs to be removed to reduce the temperature of the air.
4. This will then reduce the air conditioning costs for the factory.

Thermal Radiator

1. Thermal radiators are always used in cold country to warm the house.
2. Hot water is made to flow through a radiator. The heat given out from the radiator is then warm the air of the house.
3. The cold water is then flows back to the water tank. This process is repeated continuously.
4. Water is used in the radiator because it has high specific heat capacity.

Sea Breeze

1. Land has lower heat capacity than sea water. Therefore, in day time, the temperature of the land increases faster than the sea.
2. Hot air (lower density) above the land rises. Cooler air from the sea flows towards land and hence produces sea breeze.

Land Breeze

1. Land has lower heat capacity than sea water. During night time, the temperature of the land drops faster than the sea.
2. Hot air (lower density) above the sea rises. Cooler air from the land blows towards sea and hence produces land breeze.

Moderate Climate

1. Places with the presence of lakes, sea and ocean may have more moderate climate.
2. This is because, water has large specific heat capacity.
3. During daytime when it is hot, the water from the lake/sea absorbs heat from the surroundings. This helps to reduce the temperature of the surroundings.
4. During night-time, the water releases the heat absorbed during daytime, and hence prevents the temperature from dropping too much.
5. As such, palcess near a large mass of water will have a smaller range of temperatures and hence a more moderate climate condition.

1. Specific heat capacity is a physical quantity used to compare the heat capacity of a given material of the same mass.
2. It is the measure of how much energy can be store in 1 kg of mass of a substance.
3. Specific heat capacity is defined as the amount of heat required to change the temperature of 1 kg of a substance by 1°C.
   Mathematically, we write this as c = Q/mθ [Q = heat, c = specific heat capacity, m = mass, θ = change of temperature]
4. The SI unit of specific heat capacity is J/kg/°C.
5. For example, the specific heat capacity of water is 4200 J/kg/°C means 4200J of heat energy is needed to change the temperature of 1kg water by 1°C.
6. The amount of heat transferred in an object when temperature change can be calculated by using the following equation.

1. Heat capacity is the measure of the ability of an object to store heat as its temperature changes.
2. It is the measure of the amount of heat required to change the temperature of an object by 1°C.
   
3. The SI unit of heat capacity is joules per Kelvin (J/K).
4. The heat capacity of an object depends on the type of the material the object is made and also the mass of the object. An object with larger mass has higher heat capacity.
5. An object with higher heat capacity need more heat supplied to change 1 unit of the temperature.