Unit 4 - Energy & Heat SOL PS.6,7

Transcription

1 Unit 4 - Energy & Heat SOL PS.6,7

2 Bill Nye - Energy

3 I. PS.6a - Potential & Kinetic Energy A. Energy is the ability to do work or cause change. B. Energy is either Potential or Kinetic. a. Potential Energy is energy that is stored in an object, either due to its position, its chemistry, or some other factor. b. Kinetic Energy is energy that is being used. It is often called energy of motion, because objects with kinetic energy are usually moving. C. The Law of Conservation of Energy says that energy can never be created nor destroyed, but it can change forms. a. In other words, all the energy that has ever been in the universe is still here now, it has just changed from one form to another! b. Energy is all around us in many different forms!

4 Form of Energy Definition Example Mechanical The sum of an object s potential & kinetic energy. Its energy due to motion and position. A wind turbine being turned by the breeze. Thermal The internal energy of an object due to the kinetic energy of its atoms or particles. Food being heated by an oven. Radiant Energy of electromagnetic waves. Energy from sunlight. Chemical Energy of chemical reactions. When you throw sodium into water and it explodes. Electrical Energy released by the movement of electrons. Energy from static shocks when you touch a doorknob. Nuclear Energy released by splitting or fusing of atomic nuclei. Energy from the nuclear fusion reactions that power the Sun.

5 Mechanical Energy: The sum of an object s potential & kinetic energy. Energy due to motion & position.

6 Thermal Energy: The internal energy of an object due to the kinetic energy of its atoms or particles.

7 Radiant Energy: Energy of electromagnetic waves.

8 Chemical Energy: Energy of chemical reactions.

9 Electrical Energy: Energy released by the movement of electrons.

10 Nuclear Energy: Energy released by splitting or fusing of atomic nuclei.

11 II. PS.6b - Energy Transformations A. Energy changes forms all the time. B. Common energy transformations & how to write them: Transformation Examples Chemical Thermal/Radiant Burning firewood for heat & light Mechanical Electrical Philpott Dam or wind turbines Electrical Radiant Turning on a light Chemical Electrical/Radiant A flashlight Radiant Electrical Solar Panels C. Almost all power plants use turbines and generators to convert chemical, mechanical, or nuclear energy into electrical energy.

12 BrainPOP - Energy Sources

13 III. PS.5c - Nuclear Reactions A. The two types of nuclear energy are: a. Nuclear Fission, when the nucleus of an atom is split a) Found in all nuclear power plants b) Used in many nuclear weapons b. Nuclear Fusion, when nuclei of two atoms are fused, or combined. a) Powers the Sun b) No nuclear power plants use fusion yet, but scientists are trying to change that B. The biggest problem with nuclear fission power is where to store the nuclear waste. a. *Nuclear fusion would produce a lot less waste.*

14 III. PS.5c - Nuclear Reactions Nuclear Fission is when the nucleus of an atom is split. It is used in Nuclear Power Plants...

15 III. PS.5c - Nuclear Reactions..and Nuclear Fission is also used in nuclear weapons

16 III. PS.5c - Nuclear Reactions The biggest problem with power from Nuclear Fission is where to store the waste, which remains hazardous for hundreds of years.

17 III. PS.5c - Nuclear Reactions Nuclear Fusion is when the nucleus of an atom is fused, or combined, with the nucleus of another atom. Nuclear Fusion powers the Sun.

18 BrainPOP - Nuclear Energy

19 PHET - Energy Skate Park

20 Bill Nye - Heat

21 IV. PS.7c - Heat & Heat Transfer A. Heat is the thermal energy absorbed by an object or substance. 1. It can also be described as a flow of energy between objects of different temperatures. 2. Heat is measured in Joules (J). a) Why not in degrees? (1) Because heat IS NOT the same as temperature! B. Heat transfer is when heat moves from one object or substance to another. 1. Heat can be transferred by conduction, convection, or radiation.

22 BrainPOP - Heat

23 Conduction Convection Radiation Def: Heat transferred by direct touch. Def: Heat rising through a fluid, such as air or water. Remember: Heat rises. Example: Hot air rising, cooling, and falling, or water boiling in a pot Def: Heat transfer by electromagnetic waves, especially infrared light. Example: Touching a hot stove and getting burned, or touching a spoon in ice cream & feeling cold. A. Example: Feeling heat from a campfire 2 meters away, or heat traveling to Earth from the Sun. Thermal Expansion is when an object expands (gets larger) when it is heated and shrinks when it is cooled. 1. This is what causes cracks in pavement. 2. Water is the exception to this rule: it expands when it gets cold.

24 Conduction: Heat transfer by direct touch.

25 Convection: Heat transfer through a fluid, such as water or air.

26 Convection: Heat transfer through a fluid, such as water or air. Start this video at 2:55 to see convection in action.

27 Radiation: Heat transfer through electromagnetic waves.

28 V. PS.7a,b - Temperature A. Temperature measures the kinetic energy of all atoms or molecules in a substance. a. Temperature is measured in Degrees Fahrenheit, Degrees Celsius, or Kelvin. b. 1 degree Celsius is the same amount of temperature as 1 K, but Fahrenheit degrees are different from Celsius degrees. c. These temperatures all represent the same amount of heat, just measured differently. Degrees Fahrenheit Degrees Celsius (Correct SI units) Kelvin (Not degrees Kelvin ) Where is it used? Mainly in the U.S. Most of the world Mainly by scientists in labs What is it based on? Something random you don t need to know The Freezing & Boiling Points of Water Absolute Zero: the coldest possible temperature, where all molecular movement stops. Water Freezes at: 32 F 0 C 273 K Water Boils at: 212 F 100 C 373 K Absolute Zero F -273 C 0K

29 BrainPOP - Temperature

30 VI. PS.7b,d - Phase Changes & Technological Applications A. Matter exists in four main phases: solid, liquid, gas, and plasma. 1. The molecules in a solid are tightly packed. They don t move much. 2. The molecules in a liquid can slide past each other and take the shape of their container. 3. The molecules in a gas move very fast and fill the volume of their container. a) Plasma is superheated gas with ionized particles.

31 VI. PS.7b,d - Phase Changes & Technological Applications B. Phase Change is when a substance changes from one phase to another phase. 1. When you add heat, molecules move faster and get further apart. 2. When you subtract heat, molecules move slower and get closer together. 3. Freezing - when a liquid becomes a solid. 4. Melting - when a solid becomes a liquid. 5. Condensation - when vapor turns into a liquid 6. Vaporization - when a liquid becomes a vapor. a) There are two types of vaporization: b) Evaporation - when molecules on the surface of a liquid turn into vapor. Evaporation ONLY occurs on the surface, at temperatures below the boiling point. c) Boiling - when ALL the molecules in a liquid begin turning to vapor. Only occurs at the boiling point. 7. Sublimation - when solids turn directly into gases or vapors.

32 VII. How to Read Phase Change Charts: A. Heat added is on the x-axis, and temperature is on the y-axis. B. Temperature increases as you move to the right and decreases as you move to the left. C. The flat areas are phase changes. They are flat because: a. Temperature DOES NOT CHANGE during a phase change. This is because the energy that would normally cause temperature to increase is breaking or building the bonds between molecules that allow a phase change to occur.