If system A is in thermal equilibrium with system T and system B is in thermal equilibrium with system T, then systems A and B are in thermal equilibrium with each other.

Calorie is another unit for heat. It comes with a lower case and an upper case.

Nutritionists use the word “Calorie,” with a capital C, to specify the energy content of foods. For example, a regular 12-oz can of soda has about 140 Calories.

The cgs unit of heat is the calorie, with a lower case. One calorie (1 cal) is defined as the amount of heat needed to raise the temperature of one gram of water by one Celsius degree.

1 food Calorie = 1000 calories = 1 kcal

1 calorie = 4.186 J.

Specific Heat Capacity

Specific heat capacity of a material is the quantity of heat needed to change a unit mass of the material by a unit change in temperature. It is a property of the material.

Specific Heat Capacities of Some Common Substances

Substance

Specific heat capacity [cal/(g. C°)]

Water

1.0

Ice

0.49

Steam

0.48

Ethyl alcohol

0.58

Steel

0.11

Aluminum

0.215

Lead

0.0305

Heat Q

The heat Q that must be supplied or removed to change the temperature of a substance of mass m by an amount T is,

where c is the specific heat capacity of the substance.

Unit for Specific Heat Capacity:

SI: J/(kg · C°)

cgs: cal/(g. C°)

E6: How much heat is required to raise the temperature of 70 g of water from 20°C to 80°C?

Calorimetry

SP4: A 150-g of a certain metal, initially at 120°C, is dropped into an insulated beaker containing 100 g of water at 20°C. The final temperature of the system is 35°C.

Ignore the heat capacity of the beaker.

How much heat has been transferred to the water from the metal?

What is the specific heat capacity of the metal?

Phase Changes: Latent Heat

Latent heat changes the phase of water without changing its temperature.

Latent heat of fusion of water = Lf = 80 cal/g.

Latent heat of vaporization of water = Lv = 540 cal/g.

E8: How much heat must be added to 60-g of ice at 0°C to melt completely?