Heat and Temperature

1. Heat and Temperature Activity 1: Think about a time when you were very hot or cold. Free write about it. Underline your best words and wiggle into a poem! Make it pretty.

2. Does an ice cube have heat? • All matter has heat. Some, just more than others.

3. What Causes Heat? • Heat is caused by vibrating molecules. • Heat is defined as the total energy given off by vibrating molecules. • Molecules are always vibrating. This means all matter has heat. • How hot an object is depends on how fast its molecules vibrate. • The faster the molecules vibrate, the hotter the object will be. Eg. Boiling water

4. The Particle Theory of Matter... (PTM) Remember: • All matter is made up of tiny particles. • These particles are always moving – they have energy. The more energy they have, the faster they move. There is space between all particles. • There are attractive forces between the particles. • The particles of one substance are the same but differ from another substance.

5. Temperature: The average kinetic energy (energy of movement) of the particles of a substance.

6. Each color represents a particle of a varying speed. The average of these energies would be the temperature.

8. A Solid A GAS Why do we need to be concerned with expansion and contraction in the above pictures? A LIQUID

9. Changes of State Deposition Blue = add heat Red = lose heat

10. Graphing changes of state (a Heating Curve)

11. Changes of state and the PTM • Adding heat energy, increases the kinetic energy and therefore the temperature. • Decreasing heat energy, decreases the kinetic energy and therefore lowers the temperature.

12. 3. The particles break their attractive forces with their neighbouring particles when kinetic energy is increased.

13. 4. Eventually, the kinetic energy will be great enough to break the attractive forces holding the particles together thereby changing state. The opposite is true if heat energy is decreased.

14. Heat and Temperature

15. Heat • Heat depends on 2 things: • 1) How fast the molecules move • 2) How many molecules vibrate (Size does affect the amount of heat) • If you have a large object and a small object with the same temperature, which one will have more heat? • The larger object will have more molecules, so it will have more heat.

16. Measuring Temperatures Early Thermoscopes... 1. Galileo’s Air Thermoscope: As the air heats, the liquids drops and rises when air is cooled.

17. 2. Early Liquid Thermometer: Liquid rising up the tube shows the temperature is rising.

18. Temperature Scales • Scales are necessary for temperatures to be accurate and comparable.

19. 3 commonly used scales are: • Fahrenheit • Celsius • Kelvin

20. Fahrenheit • Developed by Daniel Fahrenheit • The first to be widely used

21. Celsius • Developed by Anders Celsius. • Based on the freezing and boiling points of water.

22. Kelvin • Developed by William Thomson (Lord Kelvin) • Scale starts at the coldest temperature possible – absolute zero (-273 ˚C)

24. Comparison chart using various temperature scales

25. Converting between Celsius and Fahrenheit

26. Converting between Celsius and Kelvin • Celsius to Kelvin: T(K) = T(°C) + 273.15 Convert 10 degrees Celsius to Kelvin: 10°C + 273.15 = 283.15 K • Kelvin to Celsius: T(°C) = T(K) - 273.15 Convert 300 Kelvin to degrees Celsius: • T(°C) = 300K - 273.15 = 26.85 °C

27. Measuring Devices 1. The Liquid-in-glass Thermometer The lab thermometer contains colored alcohol rather than mercury for safety.

28. 2. The Thermocouple • Made of two wires of different metals. • A temperature difference causes a current to flow through the wires. This current is measured by a meter.

29. Can measure higher temperatures than typical thermometers.

30. 3. The Resistance Thermometer (digital thermometers)

31. 4. Bimetallic Strip (thermostat) • Made of two different metals fused together. • These metals expand and contract at different rates causing the strip to bend when heated.

32. Thermostat

33. A Demo... Heating and Cooling a Bimetallic Strip

34. 5. Infrared Thermometer (thermogram) • Converts infrared radiation into colors that can interpret a temperature difference.

35. Can be used to measure heat loss in your home

36. Questions to Complete for next classDue Wednesday June 1 • Complete the conversion worksheet on the 3 types of temperature scales (Celsius, Fahrenheit, and Kelvin. • Read pages 80 and 81 in your textbook and complete questions 1,2 and 3. This will be due Wednesday at the beginning of class.

37. Methods of Thermal Energy Transfer Radiation Conduction Convection

38. Picture a Hot Light Bulb • Put your hand over the bulb. • What happens? Why? • Your skin is receiving thermal energy. • Heat always transfers from a hot object to a coldobject.

39. Energy Sources • The light bulb is an energy source. • An energy source is an object or material that can transfer its energy to other objects. • 3 ways in which energy can be transferred are: Radiation, Conduction, Convection

40. 3 Types of Heat Transfer

41. Radiation Transfers Energy • Radiation is the transfer of energy in a special form of wave. • Energy transferred in this way is called radiant energy and is carried by electromagnetic radiation (EMR).

42. There are no particles involved. • The waves can travel in a vacuum.

44. Types of Electromagnetic Waves

45. Characteristics • All types of radiant energy share these characteristics: • 1) They behave like waves • 2) The can be absorbed and reflected • 3) They travel at 300 000 km/s

46. Comparing Surfaces Worse Worse Better Better Better Worse Worse Better Better Better Better Worse Fill in blanks with “Better” or “Worse”

47. Conducting Energy Through Solids • In solids, are particles close together? • Thermal energy can be passed directly from one particle to the next. • Thermal conductionoccurs when the particles in an object vibrate in place but collide with neighbouring particles passing kinetic energy to them. • The particles do not leave their original position. • Conduction occurs in most solids.

48. Conducting Energy Through Solids Particles near the heat source absorb energy from it and begin moving faster

49. Conducting Energy Through Solids The fast moving particles bump into their neighbors and increase their energy/motion

50. Conducting Energy Through Solids In this way, thermal energy is transferred throughout the entire object