Specific heat capacity
The energy needed to raise the temperature of 1 kg of a substance by 1 degree C. Energy = mass x specific heat capacity x temperature change.
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Analogy
Some materials are stubborn: water takes lots of energy to warm up, copper takes very little.
Example
m = 2 kg, c = 4,200 J/kg per degreetemperature rise = 10 degreesE = 2 x 4,200 x 10E = 84,000 J
In practice
Water's high value makes it good for hot-water bottles and car coolant.
Practice
Flashcards
- Give the formula for energy needed to heat a substance.Energy = mass x specific heat capacity x temperature change.
Interview questions
- Calculate how much energy is needed to heat 3 kg of water from 20 to 30 degrees C. The specific heat capacity of water is 4,200 J/kg per degree.
- Temperature change = 10 degrees
- Use E = m x c x temperature change
- E = 3 x 4,200 x 10 = 126,000 J
Questions people ask
What does a high specific heat capacity mean?
It means the material needs a lot of energy to warm up by one degree, and also releases a lot as it cools. Water has a high value, 4,200 J/kg per degree. That is why the sea warms slowly in summer and cools slowly in autumn.
How do I use E = mc(delta T)?
Write mass in kilograms, specific heat capacity in J per kg per degree, and the temperature change in degrees C. Multiply the three to get the energy in joules. For a 0.5 kg block of aluminium (900) warmed by 20 degrees: 0.5 x 900 x 20 = 9,000 J.