1. Food and Energy The Basics of Heat Transfer

2. The Flow of Energy Thermochemistry - concerned with heat changes that occur during chemical reactions

3. Cranking up the Heat: Basic Thermodynamics Energy - capacity of an object to do work or produce heat

4. Kinetic Energy  The energy an object has due to its motion Potential Energy  Stored energy  Energy of position

5. External Energy  The energy applied to an object by another source Internal Energy  Energy within an object

6. Energy in the universe is constant, though it changes forms. Law of Conservation of energy Law of Conservation of energy – energy can neither be created nor destroyed

7. Forms of Energy Mechanical Chemical Electrical Nuclear Radiant

8. Mechanical Energy The total kinetic and potential energy of a system Examples- lifting weights, chewing food, opening the refrigerator

9. Chemical Energy The energy resulting from the forming or breaking of bonds in a chemical reaction Endothermic reaction- A reaction whose products have less total heat than the reactants Exothermic reaction- where energy is released during the reaction

10. Electrical Energy Energy that is produced by the movement of electrons Example- electricity

11. Radiant Energy Energy transmitted in the form of waves through space or some medium. Also known as the electromagnetic spectrum Examples- light, radio waves, UV waves, microwaves A microwave oven has a magnetron, which is an electron tube that converts electrical energy into microwaves The more water in food, the faster a microwave oven will cook it since the energy agitates water molecules

12. Nuclear Energy Energy from the splitting or combining of atoms of certain elements that then gives off radiation Examples- X-rays, nuclear power plants, irradiation

13. Heat vs. Temperature Temperature and heat are not the same thing. Temperature- the measure of the average kinetic energy of a group of individual molecules Heat- describes amount of energy transferred from one object to another caused by a temperature difference between the two bodies

14. Describing Energy Changes Heat flow is from the warmer object to the cooler object Heat Flow

15. Describing Energy Changes Hot day 50°C = 122°F Beans lost energy, it was transferred to its surroundings. This change of energy would be negativechange = ∆ Energy transferred from fire to beans. Change in energy for beans would be positive.

16. Endothermic reactions – absorbs heat, ∆H is positive, the surroundings cool down Exothermic reactions – releases heat, ∆H is negative, the surroundings heat up Heat Surroundings Heat Surroundings Describing Energy Changes Feels cold to the touch Feels warm to the touch

17. Heat Transfer Three methods of heat transfer Conduction- the transfer of heat through matter from particle to particle collisions Convection- the transfer of heat by the motion of fluids, such as water and air Radiation- the transfer of heat by electromagnetic waves

18. Units used to describe Energy: calorie – called “little calorie” – (cal) kilocalorie – called “Big calorie”- (CAL)  1000 calories – same as a food calorie Joule – the SI unit of heat - (J)

19. CONVERSION FACTOR 1 cal = 4.184 joules 1 cal4.184 J 4.184 J 1 cal

20. Energy Flow and Phase Changes Fusion- The movement from a solid to a liquid phase, aka melting Crystallization- The movement from a liquid to a solid phase, aka freezing Latent heat of Fusion- The energy needed to melt or freeze a substance

21. Energy Flow and Phase Changes Evaporation or Vaporization- The phase change from the liquid to the gaseous phase Condensation or Liquefaction- The change of a gas to a liquid Latent heat of vaporization- The amount of heat needed to either evaporate or condense a substance

22. Energy Flow and Phase Changes Latent heat- The energy required to complete a phase change without a change in temperature Deposition- The changing of a substance directly from a gas to a solid, ex. Frost forming on a window Sublimation- The changing of a substance directly from a solid to a gas

23. Phase Change Diagram