1. Heat Temperature

2. u Related to average kinetic energy of molecules u Measured on a scale based on some standard u Read with thermometer containing material which expands or contracts with temperature change

3. Temperature Scales u Fahrenheit: used in USA, based on freezing of sea water u Celsius (centigrade): used in most of world, based on freezing and boiling pts of water u Kelvin: SI unit of temperature for all scientific work, based on zero point volume of ideal gas

4. Temperature Scales

5. Heat u Energy that transfers from one object to another because of temperature difference u Thermal contact -- heat flows due to objects touching u Temperature difference controls direction of heat flow, not total energy

6. Thermal Equilibrium u When no heat flows between objects in thermal contact u Thermometer reaches thermal equilibrium to measure temperature

7. Internal Energy u Total energy of molecules inside substance, potential and kinetic u Objects don’t contain heat, but internal energy u Transfer of heat changes internal energy

8. Heat Quantities u Since heat is energy, it is measured in joules, the SI unit of work and energy u Quantity of heat transferred is measured by its effect -- the temp change u Temp change depends on amount and type of substance as well as quantity of heat

9. Heat Quantities u Common unit for heat measurements is the calorie: amount of heat needed to raise one gram of water one degree Celsius u Kilocalorie (1000 calories) is food Calorie, spelled with capital C u Both are units of energy: 1 cal = 4.187 J

10. Specific Heat Capacity u Quantity of heat needed to raise temp of unit mass of substance 1 o C u Different substances have different capacities for storing heat u Same amount of heat will cause different temp changes in different stuff u Acts like thermal inertia

11. Heat Quantities u Old idea of heat said that substances contain invisible fluid called caloric, released when heat given off u English unit of heat is British thermal unit (Btu), the heat required to raise the temp of 1 lb. of water 1 o F

12. Specific Heat of Water u Very high; water can store much energy without much temp rise u Also means water cools slowly u Controls climate of coastal areas, moderating temperature changes u Central continental areas have more drastic temp changes

13. Thermal Expansion u Almost all matter expands when heated, contracts when cooled: solid, liquid, and gas u Must be accounted for in construction of buildings, bridges, roads, etc. u Different materials expand at different rates

14. Thermal Expansion u Bimetallic strip: two metal strips joined together -- bends when heated due to different expansion rates -- used in thermostats, thermometers u Liquids usually expand more than solids, gases more than liquids

15. Expansion of Water u Water has abnormal expansion between 0 o C and 4 o C -- expands when cooled, contracts when heated u At all other temps, water expands and contracts normally u Water has smallest volume and greatest density at 4 o C

16. Expansion of Water u Solid form (ice) less dense than liquid, so water expands when it freezes u As water cools below 4 o C, open structure of ice starts to form, causing expansion u Very important in nature -- keeps lakes from freezing from the bottom upward and killing all aquatic life.