# Temperature, Heat, Phases, and Phase Changes

## 44 terms

### Heat

The movement of thermal energy from a substance at a higher temperature to one at a lower temperature

### Thermal contact

The state of two or more objects or substances in contact such that it is possible for heat to flow from one object or substance to another. They do not have to be touching each other.

### thermal equilibrium

The state of two or more objects or substances in thermal contact when they have reached a common temperature

### Thermodynamics

The study of energy transformations that occur in a collection of matter

### Heat Capacity

The heat required for a given increase in temperature.

### Temperature

A measure of the average energy of motion of the particles of a substance

### Zeroth law of thermodynamics

The law that if two bodies are in thermal equilibrium with a third body then the first two bodies are in thermal equilibrium with each other

### Absolute Zero

The coldest temperature, 0 Kelvin, that can be reached. It is the hypothetical temperature at which all molecular motion stops.

### calorimeter

an insulated device used to measure the absorption or release of heat in chemical or physical processes

### Conduction

the direct transfer of heat from one substance to another substance that it is touching; direct contact hear transfer. Air conducts heat also.

### Thermal Conductivity

Is the rate at which a substance transfers thermal energy. Constant k

### Insulator

A material that does not allow heat or electrons to move through it easily. Ex: glass, porcelain

### Convection

The transfer of thermal energy by the circulation or movement of a liquid or gas

Energy that is radiated or transmitted in the form of rays or waves or particles. All substances give off radiation. Waves can go through a vacuum, no need for a medium.

### Counter-current exchange

In organisms possessing two fluid systems separated by a permeable membrane across which exchange of gases or ions occurs, the occurrence of opposing fluid flow on either side of the membrane. Counter current exchange maximizes the rate of exchange. Type of conduction.

### Optical pyrometer

A pyrometer that uses the color of the light emitted by a hot object. Instrument to measure very hot temperatures. 800 C is red-hot. 3000 C is yellow-hot, this is light bulb, and 6000 C is Sun. 20000 to 30000 C is blue-hot, such as the Orion star.

The energy radiated per time by an object. Symbol is P. It is proportional to the surface area, A, over which the radiation occurs. Also depends on the temperature.

### Emissivity

e; number between 0 and 1 that is characteristic of the surface of the radiating material, Ratio of radiation emitted by a surface to the radiation emitted by a black body at the same temperature.

The result of energy radiated by an object, and radiation absorbed by said object. If object's temperature is greater than surroundings, than Pnet is positive. Rice versa. If there is equilibrium no net radiation.

### Blackbody

an object that absorbs all radiation falling on it and radiates it perfectly. e is 1. A glass that does not absorb or emit (e = 0) is the complete opposite of a blackbody.

### Ideal Gas

A hypothetical gas with molecules of negligible size that exert no intermolecular forces

### Mole

The amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12.

### Avogardro's Number

6.02x10^23, the number of atoms or molecules in one mol

### Atomic mass

Total mass of the protons and neutrons in an atom, measured in atomic mass units

### Isotherm

An ______ connects points of equal temperature with a line.

### Kinetic theory of gases

Individual gas particles will stay away from each other. They will move in the same direction until they collide. There are no attractive forces between particles collisions of particles do not cause a change in energy. Individual particles will move at different speeds but still have the same constant average velocity and kinetic energy.

### Distribution of Speeds

What remains constant as a molecule collides with other molecules.

### Internal Energy

The sum of the kinetic and potential energies of all particles in the system

### Phase Equilibrium

The state in which the rates of opposing phase changes (freezing-melting, boiling-condensation, sublimation-deposition) are equal

### Equilibrium Vapor Pressure

Pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature. Increases with temperature. For each temperature there is only one of these.

### Vapor Pressure Curve

A graph generated by plotting the temperature of a liquid on the x-axis and its vapor pressure on the y-axis. Any point on the curve represents an equilibrium between the vapor and the liquid. A liquid boils when its vapor pressure equals the external pressure.

### Phase Diagram

A graph of pressure versus temperature that shows the conditions under which the phases of a substance exist

### Triple Point

The temperature and pressure conditions at which the solid, liquid, and gaseous phases of a substance coexist at equilibrium

### Fusion Curve

The boundary between solid and liquid for any given substance as plotted on a phase diagram.

### Critical Point

The temperature and pressure at which the gas and liquid states of a substance become identical and form one phase

### Sublimation Curve

The boundary between solid and gas for any given substance as plotted on a phase diagram. Equilibrium between solids and gases.

### Evaporation

Process by which water changes from a liquid into an atmospheric gas.

### Latent Heat

Heat absorbed or radiated during a change of phase at a constant temperature and pressure

### Latent Heat of Fusion

The heat that must be extracted from a liquid to freeze it to a solid at the same temperature. For water, it is 80 cal/g

### Latent Heat of Vaporization

The heat energy required to convert a liquid to a gas at the same temperature. For water, it's 540 cal/g

### Latent Heat of Sublimation

The energy required to convert solid water to water vapor. 540 + 80 cal/g

2.108 J/g*C

### Specific Heat of Water

4.184 J/g degrees C or 1 cal/g degrees C

1.996 kJ/-kgK

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