Latent Heat Vs Specific Heat
Specific heat chapters and latent rut
A change in a cloth'due south country of thing is caused past changes to the internal energy. The size of the modify required depends on each material's 'oestrus capacity' and 'latent estrus chapters'.
Specific latent heat
Changing the internal energy of a textile will cause it to modify temperature or modify state:
- the energy required for a particular change in temperature is given past the specific heat capacity
- the energy required for a particular change in country is given by the specific latent estrus
As there can be two boundaries for modify, solid/liquid and liquid/gas, each fabric has two specific latent heats:
- latent estrus of fusion - the corporeality of free energy needed to freeze or cook the textile at its melting betoken
- latent heat of vaporisation - the amount of energy needed to evaporate or condense the fabric at its boiling point
Some typical values for specific latent heat include:
| Substance | Specific latent heat of fusion (kJ/kg) | Specific latent heat of vaporisation (kJ/kg) |
|---|---|---|
| Water | 334 | 2,260 |
| Atomic number 82 | 22.4 | 855 |
| Oxygen | 13.9 | 213 |
An input of 334,000 joules (J) of free energy is needed to change one kg of water ice into i kg of h2o at its melting point of 0°C. The same amount of free energy needs to be taken out of the liquid to freeze it.
Computing thermal energy changes
The amount of thermal energy stored or released as the temperature of a system changes can exist calculated using the equation:
change in thermal energy = mass × specific latent heat
\[ Q \\ = \\ mL \]
This is when:
- change in thermal energy ( Q ) is measured in joules (J)
- mass ( g ) is measured in kilograms (kg)
- specific latent rut ( L ) is measured in joules per kilogram (J/kg)
- Question
-
How much free energy is needed to freeze 500 grams (g) of water at 0°C?
-
\[ Q \\ = \\ mL \]
\[ Q \\ = \\ 0.five \times 334,000 \]
\[ Q \\ = \\ 167,000 \\ J \]
Measuring latent rut
Latent estrus can be measured from a heating or cooling curve line graph. If a heater of known power is used, such as a 60 watt (W) immersion heater that provides threescore J/due south, the temperature of a known mass of water ice tin can be monitored each second. This will generate a graph that looks similar this.
The graph is horizontal at two places. These are the places where the energy is not being used to increment the speed of the particles, and therefore not increasing temperature, but is existence used to break the bonds between the particles to change state.
The longer the horizontal line, the more energy has been used to cause the change of state. The amount of absorbed heat free energy represented by these horizontal lines is equal to the latent heat.
Example
If a horizontal line that shows boiling on a heating bend is 1 hour iii minutes long, how much energy has a lx W heater provided to the water?
63 minutes = 3,780 south
threescore West means 60 J of energy is supplied every 2nd
energy = power × time
energy = 60 × 3,780
energy = 226,000 J
- Question
-
If this energy had been practical to 100 one thousand of h2o, what is the specific latent rut of vaporisation of water?
-
226,000 J for 100 one thousand is equivalent to 2,260,000 J for 1 kg. The specific latent heat of vaporisation of water is 2,260,000 J/kg.
Latent Heat Vs Specific Heat,
Source: https://www.bbc.co.uk/bitesize/guides/zcpwrwx/revision/4
Posted by: sanchezyournegand.blogspot.com
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