Heat

Molecules and Motion The motion of molecules produces heat The motion of molecules produces heat The more motion, the more heat is generated The more motion, the more heat is generated

Heat expansion The expansion of a substance due to heat The expansion of a substance due to heat Most solids, liquids, and gases expand as they are heated Most solids, liquids, and gases expand as they are heated

Expansion of water Between 4ºC and 0ºC, water EXPANDS as it cools and turns into a solid Between 4ºC and 0ºC, water EXPANDS as it cools and 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 a material by one degree (Celsius). 1) C water = 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 C p Q = change in thermal energy m = mass of substance  T = change in temperature (T f – T i ) C p = specific heat of substance

Celsius Scale Celsius is the metric scale for measuring temperature Celsius is the metric scale for measuring temperature Water freezes at 0 º C and boils at 100ºC Water freezes at 0 º C and boils at 100ºC

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

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

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