Heat versus Temperature

Heat Energy transfer via random molecular motions, resulting in gain or loss of internal energy Internal energy: The total energy stores in the atoms and molecules within a substance Total energy of molecular motion in a substance Even substances that are “cold” have heat More molecules more heat energy

Temperature The property of a material that tells how warm or cold it is relative to some standard. Measure of the average energy of molecular motion in a substance In an ideal gas, the molecular kinetic energy per molecule. Heat flows from high temperature to low temperature

Heat vs. Temperature Temperature is the measurement that tells us how warm or cold something is. Temperature is directly proportional to the average translational kinetic energy of the molecules within an ideal gas Heat is energy that transfers between two things due to a temperature difference. Matter does not contain heat; rather, it contains internal energy

Temperature Conversions

Celsius scale A temperature scale with 0 as the melt-freeze temperature for water and 100 as the boil-condense temperature of water at standard pressure.

Fahrenheit scale The temperature scale in common use in the United States. The number 32 is assigned to the freezing point of water, and the number 212 to the boiling point of water (at standard atmospheric pressure)

Kelvin scale A temperature scale whose zero (absolute zero) is the temperature at which it is impossible to extract any more internal energy from a material. There are no negative temperatures on the Kelvin scale

Temperature Equations

Kinetic Molecular Theory

Kinetic Molecular Theory

Laws of Thermodynamics

0th law of thermodynamics What it says: When two systems are sitting in equilibrium with a third system, they are also in thermal equilibrium with each other In English: If a is equal to b and b is equal to c then c is equal to a

1st law of thermodynamics Whenever heat is added to a system, it transforms to an equal amount of some other form of energy The law of conservation of energy

Entropy versus Enthalpy Enthalpy: measure of heat in the system H = U + PV: where U is the amount of internal energy and P and V are the pressure and volume of the system Entropy: measure of the amount of disorder in a system The amount of energy unavailable to do work Increase in temperature increase entropy

Phases of Matter

2nd law of thermodynamics Heat does not spontaneously flow from a cold object to a hot object.

2nd law of thermodynamics No machine can be completely 100% efficient in converting energy to work; some input energy is dissipated as heat. All systems tend to become more and more disordered as time goes by. Meaning entropy is always increasing in the universe.

Specific Heat The quantity of heat required to raise the temperature of a unit of mass of a substance by one degree Celsius Measured in calories

Calorie A unit of heat. One calorie (symbol: cal) is the heat required to raise the temperature of one gram of water one Celsius degree. One Calorie (with a capital C) is equal to one thousand calories and is the unit used in describing the energy available from food.

Expansion Matter tends to expand when heated and to contract when cooled. Liquids usually expand slightly more than solids Gases expand much more than liquids or solids for comparable increases in temperature Water is highly unusual in that it contracts as it warms from 0oC to 4oC and its solid form (ice) is less dense than its liquid form