1. Ch.9
Temperature (溫度) &
Thermometer (溫度計)

2. 9.1 Temperature (溫度)
Temperature is a measure of the degree of hotness of an object.
The higher the temperature, the hotter is the object.

4. left index finger
right index finger

5. Left index finger feels cold and right index finger feels hot.5

6. right index finger
left index finger 6

7. Left index finger feels hot and right index finger feels cold.

9. Our fingers are not reliable for comparing the hotness of objects since two fingers feel different degrees of hotness even they are immersed in the same beaker of water. 9

10. 9.3 Celsius Temperature Scale (攝氏溫標)
The lower fixed point is the ice point (0 C). It is the temperature of pure melting ice at normal atmospheric pressure.
The upper fixed point is the steam point (100 C). It is the temperature of steam over pure boiling water at normal atmospheric pressure. 10

12. Class Exercise 9.1

13. Class Exercise 9.1
Y < X < Z 13

14. Calculate the temperature when the length of the mercury is 55 cm.
Class Exercise 9.2
The length of mercury in a thermometer is 40 cm at 0C and 60 cm at 100C.
Calculate the temperature when the length of the mercury is 55 cm.
Calculate the length of the mercury when the temperature is 120C. 14

16. Class Exercise 9.3

17. 10 cm 17

18. 10 cm
80 C 18

20. 20

22. 22

23. 9.4 Thermometer (溫度計)
Thermometer is a device for measuring temperature.
Different types of thermometer:
Liquid-in-glass thermometer
Expansion of liquid
Resistance thermometer
Electrical resistance of metal
Thermocouple thermometer
Electric voltage due to temperature different
Infra-red thermometer
Amount of radiation emitted by hot objects 23

25. Liquid-in-glass thermometer Resistance thermometer Infra-red25

26. Mercury-in-glass thermometer Alcohol-in-glass thermometer
can measure high temperature
(up to 357 C)
can measure low temperature
(down to -115 C)
quick response
slow response
mercury is poisonous
alcohol is not poisonous 26

27. Class Exercise 9.4
Describe briefly how you can calibrate (校準) a mercury-in-glass
thermometer in Celsius temperature scale. 27

28.  Then it is put in boiling water (upper fixed point, 100 C).
 The unmarked thermometer is first put in pure melting ice (lower fixed point, 0 C).
 Then it is put in boiling water (upper fixed point, 100 C).
 The liquid level is marked in each case.
 The separation between the two markings is divided into 100 equal divisions.
 Each division represents 1C. 28

29. Class Exercise 9.5 29

30. Class Exercise 9.5 A.
It is because heat can be conducted faster through the thinner glass wall. 30

31. Class Exercise 9.6 31

32. Class Exercise 9.6 Y.
It is because a small change in temperature will give a larger change of length of mercury. 32