Chapter 3

Kelvin scale

A temperature scale that stars at absolute zero and has the same size degrees as Celsius degrees. T (Kelvin) = T (Celsius) + 273

Celsius scale

A temperature scale with 100 degrees between the freezing point and the boiling point of water; water freezes at 0 Celsius degree and boils at 100 Celsius degree.

Fahrenheit scale

A temperature scale with 180 degrees between the freezing point and the boiling point of water; water freezes at 32 Fahrenheit degree and boils at 212 Fahrenheit degree.

The laws of Thermodynamics: Formal Statement

1. If system A is in the thermal equilibrium with system B and system B is in the thermal equilibrium with system C. Then system A is in the thermal equilibrium with system C. 2. Conservation of Energy: U=q+w 3. No process is possible whose sole result is the conversion of heat into work OR The entropy of an isolated system increase in the course of a spontaneous process. 4. The entropy of all perfect crystalline materials approaches the same constant as T approaches 0 K. Choose this value to be 0

The laws of thermodynamics: what they mean

1. You can make a thermometer 2. You can't get something from nothing. 3. You can't even break even. 4. Assign values to absolute entropies.

Thermal equilibrium

A condition where the temperatures are the same and heat no longer flows.

System

A group of interacting objects and effects that are selected for investigation. To a chemist the part of the "universe" under study is called the system.

Thermal conductor

A material that conducts heat easily.

Thermal insulator

A material that resists the flow of heat.

Temperature

A measure of the average kinetic energy of atoms or molecules. A measure of a thermal energy

Condensation

A phase change from gas to liquid, a substance in its gas phase may condense at a temperature below its boiling point.

Evaporation

A phase change from liquid to gas at a temperature below the boiling point.

Thermometer

An instrument that measures temperature

Second law of thermodynamics

Energy (heat) spontaneously flows from higher temperature to lower temperature (basic interpretation of 2nd law).

First law of thermodynamics

Energy can neither be created nor destroyed. The total energy in an isolated system remains constant; all the energy lost by one system must be gained by the surroundings or another system.

work

Force times distance mass times accel times distance N times m=J

British thermal unit (btu)

Large unit of heat used in U.S., 1 btu = 1055 joules. One Btu is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

Open system

Matter and energy can be exchanged with the surroundings.

Liquid Thermometers

Molecules move around more as the temperature increases. So, the same number molecules takes up more space at higher temperature.

Isolated system

Neither matter nor energy can be exchanged with surroundings.

Phase change

Occurs when a substance changes how its molecules are organized without changing the individual themselves. Examples are changing from solid to liquid or liquid to gas.

Calorie

Older unit of heat, 1 calories = 4.184 joules. One calorie is the amount of heat required to raise the temperature of one gram of water by one degree Celsius.

Closed system

Only energy is allowed to be exchanged with the surroundings.

Random

Scattered equally among all possible choices with no organized pattern. Random motion is motion that is scattered equally in all directions.

Converting between Celsius and Fahrenheit

T (Fahrenheit) = 9/5 T (Celius) + 32

Energy

The ability to do work thermal energy transitional energy

Relative humidity

The actual partial pressure of water vapor in air divided by the saturation vapor pressure at the same temperature.

Heat of vaporization

The energy required to change the phase of one gram of a material from liquid to gator gas to liquid at constant temperature, constant pressure, and at the boiling point.

Heat of fusion

The energy required to change the phase of one gram of a material from liquid to solid or solid to liquid at constant temperature, constant pressure, and at the melting point.

Conduction

The flow of heat energy through the direct contact of matter.

Joule

The fundamental SI unit of energy (and heat). A joule is a fairly small unit of energy.

Absolute zero

The lowest possible temperature, at which the energy of molecular motion is essentially zero, or as close to zero as allowed by quantum theory. Absolute zero is minus 273 Celsius degree or -459 Fahrenheit degree. It's not possible to have a temperature lower than absolute zero, or -273.15 Celsius degree.

Specific heat

The quantity of energy, measured in J/g·Celsius Scale, it takes per gram to raise the temperature one degree Celsius.

Triple point

The temperature and pressure at which the solid, liquid, and gas phases of substance can all exist in equilibrium together.

Boiling point

The temperature at which a substance changes phase from liquid to gas. For example, the boiling point of water is 100 Celsius degrees.

Melting point

The temperature at which a substance changes phase from solid to liquid. For example, the melting point of water is 0 Celsius degree.

Dew point

The temperature at which air is saturated with H2O vapor (Rh = 100%)

Latent heat

Thermal energy that is absorbed or released by a phase change.

Heat

Thermal energy, energy due to temperature, the total energy in random molecular motion contained in matter.

Thermistor and thermocouple

Two types of electronic sensors for measuring temperature. A thermistor is a temperature sensor that changes its electrical properties as the temperature changes. A thermocouple is another electrical sensor that measures temperature.

kineic energy

energy of motion

Brownian motion

the erratic, jerky movement of tiny particles suspended in water, due to the random impacts of individual molecules in thermal motion.