Calories (cal)

Definition

A calorie (cal) is a unit of energy. In chemistry, it is commonly used to quantify the amount of energy transferred in reactions.

5 Must Know Facts For Your Next Test

1. 1 calorie is defined as the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.
2. The relationship between calories and joules is: $1 \, \text{cal} = 4.184 \, \text{J}$.
3. Calories are often used in thermochemistry to measure heat changes in chemical reactions.
4. Nutritional calories (Calories with an uppercase C) are equivalent to kilocalories (kcal), where $1 \, \text{Cal} = 1000 \, \text{cal}$.
5. In calorimetry, the specific heat capacity of a substance is used alongside calories to determine energy changes.

Review Questions

• How many joules are equivalent to one calorie?
• What is the difference between a calorie and a nutritional Calorie?
• In what context are calories most commonly used in chemistry?

Related terms

Joule (J): A derived unit of energy in the International System of Units. One joule is equal to $1 \, \text{kg} \cdot \text{m}^2 / \text{s}^2$.

Specific Heat Capacity: The amount of heat per unit mass required to raise the temperature by one degree Celsius.

Calorimetry: The science of measuring the heat change associated with a chemical reaction or physical process.