Forms of Energy

1. Forms of Energy

2. Conduction No. 6 • The transfer of heat by direct contact between objects or particles.

3. Conduction • Thermal energy is transferred from place to place by conduction, convection, and radiation. • Conduction is the transfer of thermal energy by collisions between particles in matter. • Conduction occurs because particles in matter are in constant motion. Physical Science

4. Radiation No. 4 • Radiationis the transfer of energy by electromagnetic waves. • Heat transferred through space. • EXAMPLE: The sun’s rays causing a sunburn.

5. Radiation • Almost no matter exists in the space between Earth and the Sun, so heat cannot be transferred by conduction or convection. Instead, the Sun’s heat reaches Earth by radiation. Physical Science

7. Radiant Energy and Matter • When radiation strikes a material, some of the energy is absorbed, some is reflected, and some may be transmitted through the material.

8. Transferring Thermal Energy Radiant Energy and Matter • The amount of energy absorbed, reflected, and transmitted depends on the type of material. • Materials that are light-colored reflect more radiant energy, while dark-colored materials absorb more radiant energy. Physical Science

9. Convection • Heat transferred by the movement of molecules within a substance. • Movement occurs from warmer areas to cooler areas.

10. Convection • Liquids and gases can flow and are classified as fluids. • In fluids, thermal energy can be transferred by convection. No. 13 • Convection is the transfer of thermal energy in a fluid by the movement of warmer and cooler fluid from place to place. Physical Science

11. Convection • When conduction occurs, more energetic particles collide with less energetic particles and transfer thermal energy. • When convection occurs, more energetic particles move from one place to another. • As the particles move faster, they tend to be farther apart. • As a result, a fluid expands as its temperature increases. Physical Science

12. Convection Current • The movement of a substance that is caused by differences in temperature and density. • EXAMPLES: wind boiling water • NATURE WANTS EVERYTHING TO BALANCE ! !

13. Conduction, Convection, Radiation Physical Science

14. Physical Science

16. Conductors • Conductors are materials that transfer heat easily. • Examples: metals like copper and gold

17. Conductors • silver • copper • gold • aluminum • iron • steel • brass • bronze • mercury • graphite • dirty water • concrete Physical Science

18. Heat Conductors • The rate at which heat moves depends on the material. • Heat moves faster by conduction in solids and liquids than in gases. • In gases, particles are farther apart, so collisions with other particles occur less frequently than they do in solids or liquids. Physical Science

19. Heat Conductors • The best conductors of heat are metals. • In a piece of metal, there are electrons that are not bound to individual atoms, but can move easily through the metal. Physical Science

20. Insulators • An insulator is a material that does not transfer heat easily. • Examples: • liquids and gases • A jacket

21. Insulators • glass • rubber • oil • asphalt • fiberglass • porcelain • ceramic • quartz • (dry) cotton • (dry) paper • (dry) wood • plastic • air • diamond • pure water Insulators Physical Science

22. Physical Science

23. Temperature and Heat Matter in Motion • The faster they move, the more kinetic energy they have. • This figure shows that particles move faster in hot objects than in cooler objects. Physical Science

24. Heating and Cooling cont… No. 12 • Heat energy always moves from:HOT object COOLER object e.g.Cup of water at 20 °C in a room at 30°C - gains heat energy and heats up – its temperature rises Cup of water at 20 °C in a room at 10°C loses heat energy and cools down – its temperature will fall.

25. Temperature and Heat Temperature No. 5 • The temperature of an object is a measure of the average kinetic energy of the particles in the object. • As the temperature of an object increases, the average speed of the particles in random motion increases. Physical Science

26. Temperature • In SI units, temperature is measured in kelvin (K). • A more commonly used temperature scale is the Celsius scale. • One kelvin is the same as one degree Celsius. No. 1 • Measure of kinetic energy of molecules • Thermometer • Fahrenheit • Celsius • Kelvin Physical Science

27. Temperature and Heat Thermal Energy • The sum of the kinetic and potential energy of all the particles in an object is the thermal energy of the object. Physical Science

28. Thermal Energy • Because the kinetic energy of the butter particles increased as it warmed, the thermal energy of the butter increased. • Measurement related to the quantity of molecules. Physical Science

29. Thermal Energy and Temperature • When the temperature of an object increase, the average kinetic energy of the particles in the object increases. • Because thermal energy is the total kinetic and potential energy of all the particles in an object, the thermal energy of the object increases when the average kinetic energy of its particles increases. Physical Science

30. Thermal Energy and Mass • There are twice as many water molecules in the beaker as there are in the glass. So the total kinetic energy of all the molecules is twice as large for the water in the beaker. Physical Science

31. Thermal Energy and Mass • As a result, the water in the beaker has twice as much thermal energy as the water in the glass does. • If the temperature doesn’t change, the thermal energy in an object increases if the mass of the object increases. Physical Science

32. Heat No. 12 • Heat is thermal energy that flows from something at a higher temperature to something at a lower temperature. • Heat is a form of energy, so it is measured in joules-the same units that energy is measured in. • Heat always flows from warmer to cooler materials. Physical Science

33. Specific Heat • As a substance absorbs heat, its temperature change depends on the nature of the substance, as well as the amount of heat that is added. • The amount of heat that is needed to raise the temperature of 1 kg of some material by 1°C is called the specific heat of the material. • Specific heat is measured in joules per kilogram Kelvin [J/(kg °C)]. Physical Science

34. Specific Heat

35. Specific Heat

36. Specific Heat Equation If Q is the change in thermal energy and C is specific heat, the change in thermal energy can be calculated from the following equation:

37. Specific Heat Equation amount of heat transferred = mass x change in temperature x specific heat q = m(∆T)Cp

38. Example: Aluminum has a specific heat of 0.902 J/g x oC.   How much heat is lost when a piece of aluminum with a mass of 23.984 g cools from a temperature of 415.0 oC to a temperature of 22.0 oC? Step 1:  First read the question and try to understand what they are asking you. Can you picture a piece of aluminum foil that is taken out of an oven.  Imagine the aluminum losing heat to its surroundings until the temperature goes from 415.0 oC to  22.0 oC.

39. Step 2:  Write the original formula.

40. Step 3:  List the known and unknown factors.   Looking at the units in the word problem will help you determine which is which. q = ?m = 23.984 g∆T = (415.0 oC - 22.0 oC) = 393.0 oC     (remember, they asked for the change in temperature)Cp =  0.902 J/g x oC

41. Step 4.  Substitute your values into the formula q = ?m = 23.984 gDT = (415.0 oC - 22.0 oC) = 393.0 oC   Cp =  0.902 J/g x oC

42. Water as a Coolant • Compared with the other common materials in the table, water has the highest specific heat. • The specific heat of water is high because water molecules form strong bonds with each other. Physical Science

43. Temperature and Heat Water as a Coolant • Because water can absorb heat without a large change in temperature, it is useful as a coolant. • A coolant is a substance that is used to absorb heat. • Compared to other materials, the temperature of water will increase less. Physical Science

44. Temperature and Heat Water as a Coolant • When heat is added, some of the added heat has to break some of these bonds before the molecules can start moving faster. Physical Science

45. Temperature and Heat Measuring Specific Heat • The specific heat of a material can be measured using a device called a calorimeter. • In a calorimeter, a heated sample transfers heat to a known mass of water. Physical Science

46. Temperature and Heat Measuring Specific Heat • The specific heat of a material can be measured using a device called a calorimeter. • In a calorimeter, a heated sample transfers heat to a known mass of water. Physical Science

47. Transferring Thermal Energy Collisions Transfer Thermal Energy • Thermal energy is transferred when one end of a metal spoon is heated by a Bunsen burner. • The kinetic energy of the particles near the flame increases. Physical Science

48. Transferring Thermal Energy Collisions Transfer Thermal Energy • When heat is transferred by conduction, thermal energy is transferred from place to place without transferring matter. • Thermal energy is transferred by the collisions between particles, not by movement of matter. Physical Science

49. Transferring Thermal Energy Radiation in Solids, Liquids, and Gases • This energy then travels through the space between molecules, and is absorbed and emitted by other molecules. • Because molecules are much farther apart in gases than in solids or liquids, radiation usually passes more easily through gases than through solids or liquids. Physical Science

50. Transferring Thermal Energy Controlling Heat Flow • Almost all living things have special features that help them control the flow of heat. • For example, the Antarctic fur seal’s thick coat helps keep it from losing heat. This helps them survive in a climate in which the temperature is often below freezing. Physical Science