Heat and Energy

1. Heat and Energy • Energy is the ability to do work. • Work is done when a force causes an object to move in the direction of the force. Work is a transfer of energy. • Energy and work are expressed in units of joules (J).

2. Heat and Energy • Kinetic energy is the energy of motion. All moving objects have kinetic energy. It is the random motion of particles. • Can you give some examples?

3. Heat and Energy • Potential energy is the energy an object has because of its position. • Potential energy is STORED energy,. • Gravitational Potential Energy (GPE) is the amount of gravitational potential energy that an object has depends on its weight and its height. • Is a twisted rubber band potential or kinetic?

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5. Heat and Energy • Mechanical energy is the total energy of motion and position of an object. Both kinetic energy and potential energy are kinds of mechanical energy. • The equation to find mechanical energy is: • mechanical energy = potential energy + kinetic energy ME = GPE + KE • Could a baseball flying through the air have mechanical energy?

6. Heat and Energy • Thermal Energy is all of the kinetic energy due to random motion of the particles that make up an object. • All matter is made up of particles that are always in random motion. So, all matter has thermal energy. • Friction opposes motion and creates thermal energy. • Thermal energy increases as temperature increases. • Thermal energy increases as the number of particles increases.

7. Heat and Energy • Chemical Energy is the energy stored in chemical bonds. It changes as atoms are rearranged in chemical reactions. • Chemical energy is a form of potential energy because it depends on the position and arrangement of the atoms in a compound. • The energy in food is chemical energy.

8. Heat and Energy • Chemical energy is stored in the food you eat. Your body uses this chemical energy to function (move, make heat, make new cell/cell parts). • Energy Conversion in Plants: The chemical energy in the food you eat comes from the sun’s energy. Plants use photosynthesis to convert light energy into chemical energy, as shown on the next slide.

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10. Heat and Energy • Electrical Energy is the energy of moving electrons. Electrical energy can be thought of as potential energy that is used when you plug in an electrical appliance and use it. • Sound Energy is caused by an object’s vibrations. • So is sound potential or kinetic energy? • The object’s vibrations transmit some kinetic energy to the air particles, which also vibrate. These vibrations transmit sound energy.

11. Heat and Energy • Light Energy is produced by the vibrations of electrically charged particles. • Nuclear Energy is energy that is stored in the nucleus of an atom. • So is nuclear energy kinetic or potential? • Nuclear energy can be released when nuclei are joined in a fusion reaction. The sun is a fusion reactor. • Nuclear energy can be released when a nucleus is split apart in a fission reaction. A nuclear power plant uses the fission of uranium as a heat source.

12. Heat and Energy • An energy conversion is a change from one form of energy to another. Any form of energy can change into any other form of energy. • Conversions Involving Electrical Energy Some common energy conversions that involve electrical are………….Give some examples?

13. Energy Conversions: Examples • Alarm clockelectrical energy  light and sound energy • Batterychemical energy  electrical energy • Light bulbelectrical energy  light and thermal energy • Blenderelectrical energy  kinetic and sound energy • Hair Dryerelectrical energy  thermal energy, sound energy and kinetic energy

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15. Heat and Energy • Law of Conservation of Energy states that energy cannot be created nor destroyed

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18. Heat • Temperature is a measure of the average kinetic energy of the particles in an object. • All matter is made of atoms or molecules that are always moving. • The faster the particles are moving, the more kinetic energy they have. The more kinetic energy the particles of an object have, the higher the temperature of the object is.

19. Heat • Thermal expansion is the increase in volume of a substance in response to an increase in temperature. • As a substance’s temperature increases, its particles move faster and spread out. They take up more space and so have a larger volume. • D = mass/volume • So does the density of the substance do up or down during thermal expansion? • More volume = bigger number on the bottom. Divide by a big number = a small numberSo the density goes down.

20. Heat • Temperature Scales Three common temperature scales are the Celsius scale, the Fahrenheit scale, and the Kelvin scale. • The Kelvin scale is the official SI temperature scale. unit = kelvin (K) • The lowest temperature on the Kelvin scale is O K, which is called absolute zero.

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22. Heat • Thermal Conduction is the transfer of thermal energy from one substance to another through direct contact. Conduction can also occur within a substance. • The particles of substances as different temperatures have different average kinetic energies. When such substances touch, their particles collide • Thermal conductivity is a physical property or a physical change?

23. Heat • Convection is the transfer of thermal energy by the movement of a liquid or a gas. The gas or the liquid will circulate. • As water is heated, it becomes less dense. The warmer water rises through the cooler water above it. • At the surface, the warm water cools and becomes more dense. The cooler water then sinks to the bottom and the cycle repeats.

24. Heat • Radiation is the transfer of energy by electromagnetic (EM) waves. All objects radiate EM waves. • Unlike conduction and convection, radiation can involve either a transfer of energy between particles of matter or an energy transfer across empty space.

25. Heat • Where is the radiation?

26. Heat • Thermometer, conduction, thermal energy, thermal expansion temperature, heat, radiation

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