heat, chap 7 form 1

1. The sun is the primary source of hear.
2. The sun gives out light and heat to the earth
3. Heat is a form of energy that causes an object to become hot
4. the unit of heat is joule (J)
5. Temperature is the degree of hotness or coldness of an object
6. The SI unit for temperature is kelvin (K)
7. A thermometer can be used to measure the temperature of a substance or an object in degree celsius ('c)
8. Different substances of the same temperature may have different amounts of heat
9. Solids liquids and gases expand when they are heated and contract when they are cooled
10. Gases expand more than liquids when heated
11. Liquids expand more than solids when heated
12. The transfer of heat can occur through conduction, convection and radiation
13. Conduction is a process of heat transfer from hot to cold areas through solids. It occurs very well in metals.
14. Conductors of heat are substances which conduct heat well.
15. Insulators of heat are materials that do not conduct heat well
16. Metals are good conductors of heat and non metals are good insulators of heat
17. Convection is a process of heat transfer in fluids
18. Radiation is a process of heat transfer from a source of heat to the environment without any medium invovled
19. heat causes changes in the state of matter
20. the state of matter changes from a solid to a liquid and then to a gas when heated
21. When matter cools down, it changes from gas to liquid and then to a solid
22. The physical processes involved in the changes of state of matter are melting, boiling freezing evaporation condensation and sublimation
23. The type of surface of an object influences the rate of absorption and radiation of heat by the object
24. dull and black surfaces are good absorbers and radiators of heat
25. shiny and white surfaces are good reflectors of heat but poor absorbers and radiators of heat
26. the principle of heat flow benefits humans. we should be grateful for our comfortable lives