HeatHeat

Molecules and MotionMolecules and Motion

The motion of molecules The motion of molecules produces heatproduces heat

The more motion, the The more motion, the more heat is generatedmore heat is generated

Heat expansionHeat expansion

The expansion of a The expansion of a substance due to heatsubstance due to heat

Most solids, liquids, and Most solids, liquids, and gases expand as they are gases expand as they are heatedheated

Expansion of waterExpansion of water

Between 4ºC and 0ºC, Between 4ºC and 0ºC, water EXPANDS as it cools water EXPANDS as it cools and turns into a solidand turns into a solid

Thermal Energy

A. Temperature & Heat

1. Temperature is related to the average kinetic energy of the particles in a substance.

3. Thermal Energy – the total of all the kinetic energy of all the particles in a substance.

4. Thermal energy relationships

a. As thermal energy increases, so does temperature (because the kinetic energy of the particles increased).

b. Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy).

5. Heat

a. The flow of thermal energy from one object to another.

b. Heat always flows from warmer to cooler objects. Ice gets

warmer while hand gets

cooler

Cup gets cooler while hand gets

warmer

6. Specific Heat

a. Some things heat up or cool down faster than others.

Land heats up and cools down faster than water

b. Specific heat is the amount of heat required to raise the temperature of 1 g of a material by one degree (Celsius).

1) C water = 4.184 J / g C

2) C sand = .664 J / g C

This is why land heats up quickly during the day and

cools quickly at night and why water takes longer.

How to calculate changes in thermal energy

Q = m x T x Cp

Q = change in thermal energy

m = mass of substance

T = change in temperature (Tf – Ti)

Cp = specific heat of substance

Celsius ScaleCelsius Scale

Celsius is the metric scale Celsius is the metric scale for measuring temperaturefor measuring temperature

Water freezes at 0Water freezes at 0ººC and C and boils at 100ºCboils at 100ºC

Kelvin scaleKelvin scale

The Kelvin scale is a metric The Kelvin scale is a metric temperature scale measured temperature scale measured in Kelvin units (K)in Kelvin units (K)

Absolute zeroAbsolute zero

The temperature in which The temperature in which all molecular motion stops all molecular motion stops (0 K)(0 K)

Temperature Conversion FormulasTemperature Conversion Formulas

Kelvin = C + 273Kelvin = C + 273 Celsius = K – 273Celsius = K – 273 Celsius = (5/9)*(F – 32) Celsius = (5/9)*(F – 32) Fahrenheit = (9/5)*C+ 32Fahrenheit = (9/5)*C+ 32