Thermal Energy Flashcards

All 7 cards in this deck

What is the equation for the energy stored in or released from a system as its temperature changes?

$\Delta E = mc\Delta\theta$ (mass × specific heat capacity × temperature change)

What is the specific heat capacity of a substance?

The amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

What are the units of specific heat capacity?

J/kg °C (joules per kilogram per degree Celsius).

What are the steps to calculate the energy needed to heat a substance?
e.g. 2 kg of water heated by 10 °C, $c = 4200$ J/kg °C

1. Write $\Delta E = mc\Delta\theta$
2. Substitute: $2 \times 4200 \times 10$
3. $\Delta E = 84\,000$ J

What are the steps to calculate a specific heat capacity from measurements?
e.g. 26 000 J raises the temperature of 2.0 kg of iron by 26 °C

1. Rearrange: $c = \dfrac{\Delta E}{m\Delta\theta}$
2. Substitute: $c = \dfrac{26\,000}{2.0 \times 26}$
3. $c = 500$ J/kg °C

True or false? Of two equal masses, the one with the higher specific heat capacity needs more energy for the same temperature rise.

True. More energy is needed per kilogram per degree Celsius.

True or false? In $\Delta E = mc\Delta\theta$, the mass must be in grams.

False. The mass must be in kilograms.