Chapter 8: Energy

Thermodynamics

The study of energy and temperature changes.

Energy

The ability to do work.

Potential energy

Stored energy.

Kinetic energy

Energy of motion.

Heat

The transfer of kinetic energy.

Work

The transfer of energy from one form to another.

Units of Energy

1 joule (J) = 1 kg.m²/s², 1 calorie (c) = 4.184 J, 1,000 calories = 1 kcal = 1 Calorie.

Change in Energy

ΔE = q + w, where ΔE is the change in energy, q is heat released, and w is work done.

Exothermic change

Releases heat energy, feels hot.

Endothermic change

Absorbs energy, feels cold.

System

The part of the universe being studied (reaction).

Surroundings

The rest of the universe (everything else).

Ice example

Ice is the system, absorbs heat from the surroundings.

Direction of Energy and Work Changes

Exothermic change (-q), Endothermic change (+q), System does work on surroundings (-w), Surroundings does work on system (+w).

The Law of Conservation

Energy cannot be created or destroyed, only change forms and be transferred. ΔE system = -ΔE surroundings.

Heat

The total kinetic energy transferred from one substance to another.

Temperature (T)

The average kinetic energy of the particles in a substance.

Specific Heat (s)

The amount of heat required to raise the temperature of 1 gram of material by 1 degree Celsius. s = q/(mΔT).

Heat Capacity (C)

The amount of heat required to raise an object by 1 degree Celsius. C = q/ΔT.

Calorimetry

Measure the flow of heat. Coffee cup calorimetry and bomb calorimetry.

Fuel value

The amount of energy produced by the combustion of a material.

Reaction Enthalpy (ΔHrxn)

The amount of heat energy absorbed or released in a chemical reaction at constant pressure.