Specific Heat and Thermal Energy Transfer Chp. 6 and 16 notes continued.

Changes of matter: You already know most of these.  Solid -> liquid = melting  Liquid -> gas = vaporization  Solid -> gas (skipping the liquid phase) = sublimation  Gas -> liquid = condensation  Liquid -> solid = freezing  Gas -> solid (skipping the liquid phase) = deposition  Endothermic: energy goes into something.  Exothermic: energy goes out of something.

Specific Heat  Some things heat up or cool down faster than others.  Land heats up and cools down faster than water.

Specific Heat  Specific heat is the amount of heat required to raise the temperature of 1 kg of a material by one degree (C or K). 1) 1) Specific Heat water = 4184 J / kg C 2) Specific Heat sand = 664 J / kg C THIS IS WHY WATER IS ABLE TO MAINTAIN ITS TEMPERATURE FOR SO LONG. EVEN WHEN LAKES OR POOLS FREEZE OVER, THE WATER AT THE BOTTOM DOESN’T FREEZE.

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

Practice:  How much energy must be gained for 2 kg of water to raise from 23 degrees Celsius to 26 degrees Celsius?  How much energy must be lost in order for 20 kg of sand to go from 28 degrees Celsius to 20 degrees Celsius?

Calorimeter  A calorimeter is used to measure the specific heat of a substance. If the energy, mass, and temperature are known, the specific heat can be found.

Thermal Energy Transfer:  Conduction: Heat transfer by ______. Objects that increase in thermal energy have their particles move more rapidly.  Convection: Heat transfer by fluid movement around the substance. Convection is the transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy along with its mass. Although the heat is initially transferred between the object and the fluid by conduction, the bulk transfer of energy comes from the motion of the fluid.  Radiation: Energy that comes from a source and moves through some other media like the air or space. Examples are light, sound, and heat.

Insulators and Conductors  A heat insulators keeps heat contained in a desired area.  What are some good insulators?  A heat conductor transfers heat easily from one substance to another.  What are some good conductors?

Phase Change Diagrams:

What does this mean in terms of molecular motion?  What is molecular motion?  What happens to the motion of molecules as energy is added to them? What happens to the temperature of the molecules?