Temperature and internal energy
Internal energy
- Particles in a solid vibrate about fixed position and are held together by strong intermolecular bonds. The total energy of these particles is called internal energy
- made up of two components – kinetic and potential energy
Kinetic component of internal energy
- due to vibration of particles
- The higher the temperature, the more vigorous the vibrations of particles
Potential component of internal energy
- due to the stretching and compressing of intermolecular bonds as the particles vibrate
- amount of potential energy stored in bonds depends on force between the particles and how far the particles are.
Melting and Solidification
Melting
Melting
- a process whereby when the solid state change to liquid state.
- The melting point of ice is 0, the constant temperature of which ice melts to become water.
- Although thermal energy is being absorbed during the change of state, the temperature remains the same.
Solidification
- solidification is basically a process changing from a liquid to solid state
- a pure substance will solidify or freeze at a temperature equal to its melting point.
- during the change of state from liquid to solid, there is no change in temperature even though thermal energy is lost to the surroundings.
Boiling
- Heating curve
When a state is heated and it changes to a vapor at a constant temperature, it is known as boiling.
(From the heating curve)The temperature remains steady at 100 degree celcius as the water boils and changes into gas/steam. This constant temperature at 100 degree celcius is the boiling point of water. During the change of state from water to vapor, there is no change in temperature even though thermal energy is being absorbed.
Condensation
Condensation is the change of state from vapor to liquid when a substance is cooled at the same constant temperature as in boiling. Thermal energy is given out during condensation.
Evaporation
Evaporation
- occurs at any temperature
- slow process
- takes place only at the liquid surface
- requires thermal energy from surroundings
applications of evaporation
- able to experience cooling effect on skin when perspiration evaporates
- wet clothes or puddles of water on pavements dry up after a while
- a person with high fever is sponge with water as when water evaporates, the temperature of patient can be kept down.
- Refrigerator uses principles of condensation and evaporation to keeps its content cold.
Factors affecting evaporation
- temperature > a higher temperature will increase the rate of evaporation
- humidity of surrounding air > Rate of evaporation decreases with increasing humidity
- surface area of liquid > rate of evaporation increases when there is more exposed surface area of the liquid
- movement of air > rate of evaporation also increases when the surrounding air is moving.
- Pressure > reducing atmospheric pressure increases the rate of evaporation
- Boiling point of liquid > liquids with lower boiling points will evaporate faster
Internal energy
- Particles in a solid vibrate about fixed position and are held together by strong intermolecular bonds. The total energy of these particles is called internal energy
- made up of two components – kinetic and potential energy
Kinetic component of internal energy
- due to vibration of particles
- The higher the temperature, the more vigorous the vibrations of particles
Potential component of internal energy
- due to the stretching and compressing of intermolecular bonds as the particles vibrate
- amount of potential energy stored in bonds depends on force between the particles and how far the particles are.
Melting and Solidification
Melting
Melting
- a process whereby when the solid state change to liquid state.
- The melting point of ice is 0, the constant temperature of which ice melts to become water.
- Although thermal energy is being absorbed during the change of state, the temperature remains the same.
Solidification
- solidification is basically a process changing from a liquid to solid state
- a pure substance will solidify or freeze at a temperature equal to its melting point.
- during the change of state from liquid to solid, there is no change in temperature even though thermal energy is lost to the surroundings.
Boiling
- Heating curve
When a state is heated and it changes to a vapor at a constant temperature, it is known as boiling.
(From the heating curve)The temperature remains steady at 100 degree celcius as the water boils and changes into gas/steam. This constant temperature at 100 degree celcius is the boiling point of water. During the change of state from water to vapor, there is no change in temperature even though thermal energy is being absorbed.
Condensation
Condensation is the change of state from vapor to liquid when a substance is cooled at the same constant temperature as in boiling. Thermal energy is given out during condensation.
Evaporation
Evaporation
- occurs at any temperature
- slow process
- takes place only at the liquid surface
- requires thermal energy from surroundings
applications of evaporation
- able to experience cooling effect on skin when perspiration evaporates
- wet clothes or puddles of water on pavements dry up after a while
- a person with high fever is sponge with water as when water evaporates, the temperature of patient can be kept down.
- Refrigerator uses principles of condensation and evaporation to keeps its content cold.
Factors affecting evaporation
- temperature > a higher temperature will increase the rate of evaporation
- humidity of surrounding air > Rate of evaporation decreases with increasing humidity
- surface area of liquid > rate of evaporation increases when there is more exposed surface area of the liquid
- movement of air > rate of evaporation also increases when the surrounding air is moving.
- Pressure > reducing atmospheric pressure increases the rate of evaporation
- Boiling point of liquid > liquids with lower boiling points will evaporate faster
End OF UNIT 9. BYES
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