1. Temperature and Thermal Energy

2. Temperature Temperature – average K.E. of the particles in a sample. Depends on the size of the particles and their velocity (½ mv 2 ). Temperature  Ave. K.E. of particles  Does not depend on the mass of sample : (total number of particles).

4. Measure using a thermometer Celsius : °C Water freezes at 0°C Water boils at 100°C (at 1 atm pressure) Kelvin : K Water freezes at 273.15 K Water boils at 373.15 K (at 1 atm pressure) T = 273.15 + T C Fahrenheit : °F Water freezes at 32°F Water boils at 212°F (at 1 atm pressure)

6. Kelvin was developed to work with gases. No negative temperatures. Absolute zero : 0 K, lowest temperature, no motion of particles (or anything).

7. Internal Energy Kinetic Molecular Theory – matter is made up of tiny particles that are in constant motion. States of Matter – solids, liquids, gases, plasma State of matter depends on the temperature and the forces holding the particles together.

8. Internal Energy – the total amount of energy of the particles in a sample. Symbol : U Units of Joules, J Depends on: 1.Kinetic energy of the particles (temperature) Translational, Rotational, Vibrational 2.Mass of sample (number of particles)

9. Heat Transfer of energy between two objects because of a difference in their temperatures. Heat flows from hot objects to cold objects. Changes the internal energy (  U) and the temperature (  T) of the sample. Symbol : Q Units : Joule (J) calorie (cal) = 4.186 J Calorie (food calorie) = 1 kcal = 4.186 kJ British thermal unit (Btu) = 1.055 kJ

10. Transferring Energy Energy is transferred by conduction, convection, and radiation. Conduction – transfer of the K.E. when particles collide. Matter must touch. Works best in solids. Thermal conductors – metals Thermal insulators - wood

11. Convection – transfer of energy because of the movement of fluids. Fluids move because of a change in density. Hot air rises, cold air settles. Causes changes in weather. Works best in liquids and gases.

12. Sea Breeze Land Breeze

13. Radiation – transfer of energy by electromagnetic waves. Solar energy - no matter is needed. Energy is absorbed and then the matter gets warm.

14. Thermal Equilibrium Thermal Equilibrium – the rate that energy flows from one sample to another is the same as the rate the energy flows back. Objects have the same temperature Objects may not have the same internal energy Place a hot metal into cold water, they have reached thermal equilibrium when they reach the same temperature. One object lost energy and one object gained energy.

16. Specific Heat Capacity SubstanceSpecific Heat J/kg°C T i °C T f °C  T °C Copper3852537.9912.99 Aluminum9032530.545.54 Methanol24502527.042.04 Water41862526.201.20 Hydrogen14,2982525.350.35 Add 5000 J of energy to 1.0 kg of each of the following substances.

17. Specific Heat Capacity – the amount of energy required to raise 1 kg of a substance 1°C. The capacity of a substance to absorb energy for given change in temperature. Symbol : C p (constant pressure) Units :

18. Substances with high C p will absorb large amounts of energy for a given temperature change. Substances with a low C p can only absorb a small amount of energy for the same temperature change. Water is used as a coolant because it can absorb large quantities of heat without a large change in temperature. Hydrogen is also a good coolant, but it is explosive!

19. You bite into a hot pizza that just came out of the oven. The crust and the toppings are all at the same temperature. The roof of you mouth is burned, but you tongue is not. Why? Topping is mostly water, it contains more energy than the crust because it has a higher capacity of heat than the bread that has very little amount of water.

20. One to remember! Specific Heat SubstanceJ/kg °CSubstanceJ/kg °C Aluminum903Lead130 Brass376Methanol2450 Carbon710Silver235 Copper385Steam2010 Glass664Zinc388 Ice2090Water4186 Iron450

21. The amount of energy transferred as heat depends on the specific heat capacity, the mass and the change in temperature. Q = mC p  T Q = mC p (T f – T i ) T f > T i gaining energy +Q (getting hot) T f < T i losing energy -Q (getting cold) C p for water is 4186 J/kg°C.