1. Internal energy, Temperature & Heat Salman Al-beshan

2. Internal energy -the type of motion depends on whether the material is solid, liquid or gas. -in the solid the molecules move in fixed position, this is the reason why solid do not change their shape easily. -in liquids and gases the molecules move randomly, this is the reason why liquids and gases change their shape easily. 2

3. Solid, liquid and gas 3

4. Internal energy -because these molecules are moving, they have kinetic energy, and this molecules also have potential energy because of the force attracting between them. -so, the total kinetic energy and potential energy of the molecules called internal energy. 4

5. What is Temperature? Temperature (T) is a measure of how “hot” or “cold” something is. Temperature is not energy nor is it heat. Temperature is a measure of the motion of the atoms/molecules that make-up an object. –The greater the motion/vibration the greater the T –The smaller the motion/vibration the lower the T 5

6. Temperature If the temperature of substance is increased, it expand. If the temperature of substance is decreased, it contract. If the temperature of solid is increased, it melts. If the temperature of liquid is increased, it boils. 6

7. Scales of temperature Temperature is measured in 3 common scales: 1-Celsius or Centigrade ( o C) 2-Fahrenheit ( o F) 3-Kelvin (K) (SI unit of temperature) {note: units of Kelvin are not degrees K (or o K), just K} 7

8. 1-Celsius or Centigrade ( o C) -Divides the range between melting point and boiling point into 100 degree(100 o C). -The temperature of melting ice is 0 o C. -The temperature of boiling water is 100 o C. 8

9. 1-Celsius or Centigrade ( o C) 9

10. 2-Kelvin (K) -The temperature of melting ice is 273.15K. -The temperature of boiling water is 373.15K. -The significance of this scale is that at 0K the particles which are normally in motion are at rest. That mean at 0K a body has no internal energy. 10

11. 2-Kelvin (K) -This temperature, which has never been achived,is known as absolute zero. - absolute zero is the lowest physical achievable temperature. 11

12. 2-Kelvin (K) 12

13. Comparison between K & o C 13

14. 3-Fahrenheit scale -Divides the range between melting point and boiling point into 180 degree. -The temperature of melting ice is 32 o F. -The temperature of boiling water is 212 o F. 14

15. Fahrenheit scale 15

16. Body temperature 16 FahrenheitKelvinCentigradeTemperature scale 98.4 o F310K37 oC Body temperature

17. 17 Comparison between temperature scales

18. Latent heat -a solid at a melting point or a liquid at boiling point can absorb energy without a rise of temperature. for example, liquid which freezes into a solid, can release energy without suffering a fall of temperature. -This the energy is used to achieve the rearrangement of particles which change the physical state. 18

19. Latent heat -This energy is called latent heat. -For example: to melt 1kg of ice(at 0 o C)into water also(at 0 o C)required about 330kilojoules of energy. 19

20. Heat Capacity: -It is the change in internal energy accompanies a one-unit temperature change in the body. - heat capacity(c)= internal energy change ÷ temperature change = J ÷ K = J K -1 20

21. Specific Heat Capacity -It is the property of a material or substance rather than a body or object. - specific heat capacity = Internal energy change ÷ (temperature change×mass) = J kg -1 K -1 21

22. Specific Heat Capacity –Metals tend to have low specific heat capacities (which is one reason they make great cooking vessels) –Non-metal substances tend to have higher specific heat capacities 22

23. Specific Heat Capacity 23

24. Specific Heat Capacity Example. The anode disc of an X-ray tube is made of molybdenum and has a mass of 0.7kg.during a very rapid angiographic exposure series, estimate the approximate temperature rise if the specific heat capacity is 250 kg -1 K -1 ? 24

25. Conduction,Convection&Radiation -There are 3 mechanisms through which energy is transferred by heat,Conduction,Convection and Radiation. -Conduction is the dominate in solid. -Convection is the dominate in liquid. - Radiation is the dominate in vacuum 25

26. Conduction,Convection&Radiation 26

27. Conduction -It is the transfer of thermal energy between neighboring molecules in a substance through direct contact. -When cooking on the stovetop, the heat from the flame is applied directly to the frying pan. This means that only the flat surface of the pan is sufficiently hot enough to cook anything. 27

28. Convection -It is movement of molecules within fluid. -Air or water surrounding a heat source receives heat, becomes less dense and rises. The surrounding, cooler fluid moves to replace it. This cooler fluid is then heated and the process continues, forming a convection current. 28

29. Radiation - electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. - represents the transfer of heat by electromagnetic radiation, The sun is example of radiating objects producing heat. 29

30. Thank you for your attention 30