Specific Heat Capacity
- Created by: theninjaemu
- Created on: 10-07-17 16:37
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- Specific Heat Capacity
- Defining SHC
- The energy required per unit mass to change the temperature of a substance by 1K and has units J/Kg/K
- Water has an SHC of 4200J/Kg/K
- Energy supplied = mass x SHC x change in temperature
- Determining SHC
- Use an electrical circuit with a heater placed in a substance
- Ammeter connected in series
- Voltmeter connected in parallel with the heater
- Variable resistor to control current
- Use an insulator to minimise the energy lost to surroundings
- For liquids, stir the liquid carefully to ensure the temperature is uniform throughout
- Energy transfered or supplied is equal to current x p.d. x time
- SHC is calculated using the equation: c = (IVt)/(m x temp. change)
- Use an electrical circuit with a heater placed in a substance
- Temperature-time graphs
- For any time, the SHC equation can be written as: E/t = mc x (temp. change)/t
- (temp. change)/t is the gradient of the graph
- E/t is the constant power supplied
- This means that P = mc x gradient
- Re-arrange this to give: c = P/(m x gradient)
- Method of mixtures
- Another way to determine SHC
- Known masses of 2 substances are mixed together
- Recording their final temperature at thermal equilibrium allows the SHC of one substance to be found if the SHC if the other is known
- The energy transfered from one substance = energy transfered to the other substance
- Constant-volume-flow heating
- A technique used to heat a fluid passing over a heated filliament
- Liquids are in compressible, so a given volume is equal to a given mass
- This means the flow rate is the mass flowing through a pipe and passing over the heater per unit time (Kg/s)
- For this, the SHC equation becomes E/t = (m/t) x c x temp. change
- Defining SHC
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