# Thermodynamics

Thermodynamics is a branch of physics that has relationships between heat and energy. It is converted to and from other types of energy and it affects matter. Thermal energy is the energy a substance has due to its temperature.

# Heat

Heat is energy that's transferred between systems due to a temperature difference. Heat can not be created or destroyed but it can be it can be transferred from one place to another.

# Temperature

With temperature it has atoms and molecules which deals with energy. The most commonly used temperature scale is Celsius which is based on the freezing and boiling points of water. The Fahrenheit scale is also based on the freezing and boiling points of water.

# Specific Heat

For instance, a kilogram of aluminum can absorb about seven times more heat than a kilogram of lead. However, lead atoms can absorb only about 8 percent more heat than an equal number of aluminum atoms. The specific heat of a gas is more complex and depends on whether it is measured at constant pressure or constant volume.

# Thermal conductivity

These materials, such as rock wool, goose down and Styrofoam, are used for insulation in exterior building walls, winter coats and thermal coffee mugs. Other materials are useful because they are extremely poor conductors of heat; this property is referred to as thermal resistance, or R-value, which describes the rate at which heat is transmitted through the material.

# Newton's Law of Cooling

This results in an exponential decay in the temperature difference. For example, if a warm object is placed in a cold bath, within a certain length of time, the difference in their temperatures will decrease by half. This repeated halving of the temperature difference will continue at equal time intervals until it becomes too small to measure.

# Heat transfer

Heat can be transferred from one body to another or between a body and the environment by three different means: conduction, convection and radiation. Conduction between bodies occurs when they are in direct contact, and molecules transfer their energy across the interface.

# The Carnot cycle

volume and temperature of gasses and how an input of energy can change form and do work outside the system. Compressing a gas increases its temperature so it becomes hotter than its environment. Heat can then be removed from the hot gas using a heat ex changer. This is the basic principle behind heat pumps used for heating, air conditioning and refrigeration.

# Entropy

All thermodynamic systems generate waste heat. This waste results in an increase in entropy. Entropy in any closed system always increases. You can mix hot and cold water, but because a large cup of warm water is more disordered than two smaller cups containing hot and cold water, you can never separate it back into hot and cold without adding energy to the system.