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• Created by: Anna
• Created on: 02-01-13 12:50

Evaporation and condensation

Evaporation is when a liquid turns into a gas. Evapouration takes place because the most energetic liquid molecules escape from the liquids surface and enter the air. Therefore, the average kinetic energy of the remaining molescules is less, so the temperature of the liquid decreases. This means that evaporation causes cooling.

The rate at which evaporation takes place is increased by:

- increasing the surface area of the liquid.

- increasing the temperature of the liquid

- creating a draught of air across the liquids surface

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Evaporation and condensation (cont.)

Condensation is when a gas turns into a liquid. This often takes place on cold surfaces such as windows and mirrors.

Like Evaporation, the rate at which condensation takes place can be increased by:

- increasing the surface area

- reducing the temperature

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specific heat capacity

When we heat a substance, we transfer energy to it which will increase its temperature. The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kilogram of the substance by 1 degree Celcius.

Different substances have different specific heat capacities. The greater the specific heat capacity, the more energy required for each degree temperature to change. For example the specific heat capacity of aluminium is 900 J/kg degrees Celcius and of copper is 490 J/kg degrees celcius. If we wanted to raise the temperature of 1 kg of aluminum we would need to transfer twice as much energy needed to raise the temperature of 1kg of Copper by the same amount.

The greater mass of substance being heated the more energy required for each degree temperature change.

The equation for specific heat capacity: E= m x c x 0 (feta)

E is energy transfered in J, m is mass in kg, c is specific heat capacity J/kg degrees celcius, 0 (feta) is temperature change

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Inside a fossil fuel factory

Coal --> burnt in frunace --> steam created is used to power turbine (steam also condensed into water to be turned into steam again) --> generator -->  power lines ( national grid)

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Musical sounds

The pitch of a note depends on the frequency of the sound waves. The higher the frenquency of the wave the higher the pitch of the sound.

The loudness of a sound depends on the amplitude of the sound waves. The greater the amplitude the more energy the wave carries and the louder the sound.

Difference in waveform can be shown on an oscilloscope.

tunning forks and singnal generators produce "pure" wave forms. The quality of a note depends on the waveform. Different instruments produce different waveforms that is why they sound different from each other. Vibrations created in an instrument when it is played produce sound waves.

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