Heat and Temperature — Specific Heat, Latent Heat and the Three Ways Heat Travels

Heat Is Not Temperature — Start Here

A burning matchstick is at roughly 800 °C. A bucket of water at 60 °C is far cooler, yet it holds vastly more heat. That single comparison contains the whole distinction:

• ›Heat is the *total* energy transferred because of a temperature difference. It depends on how much substance you have. SI unit: the joule (J).
• ›Temperature is the *average* kinetic energy of the particles. It does not care about quantity. SI unit: the kelvin (K).

The older unit is the calorie, the heat needed to raise 1 gram of water by 1 °C. Remember 1 calorie = 4.18 J, near enough 4.2.

Heat always flows from the hotter body to the colder one, never the reverse on its own, and it keeps flowing until both reach the same temperature — thermal equilibrium. Every question in this chapter is an application of that one sentence.

1. Which of the following is the SI unit of heat?

2. At what temperature do the Celsius and Fahrenheit scales show the same numerical reading?

3. A lake freezes at the surface in winter, yet fish survive below the ice. The property of water responsible for this is that water

4. A body is at 27 °C. What is its temperature on the Kelvin scale?

5. Steam at 100 °C produces a more severe burn than water at 100 °C because

6. Heat from the Sun reaches the Earth mainly by which mode of transfer?

7. How much heat is required to raise the temperature of 2 kg of water by 10 °C? (specific heat of water = 4200 J/kg·°C)

8. The latent heat of fusion of ice is approximately