GRADE 7

1. HEAT AND
TEMPERATURE
7TH GRADE
AL WILDAN ISLAMIC SCHOOL 3 BSD CITY

2. Consept Map
Temperature
and Heat
Temperature
and Scale
Thermometers
Thermal
Expansion
Measuring
Heat Energy
Heat Transfer

3. Temperature and scales
 Temperature : measure of the degree of hotness
or coldness of an object
 Temperatured is measured in Celsius,
Fahrenheit, Reamur and Kelvin
 Ice point: which is temperature of pure melting
ice at standard atmospheric pressure. The value
is 0 ⁰C
 Steam point: which is temperature of boiling
water change into steam at standard
atmospheric pressure. The value is 100 ⁰C

4. Temperature conversions
C : R : F : K
5 : 4 : 9 (+- 32) : ( C+- 273)

5. Convert this!
 40 ⁰C = …… ⁰R = …… ⁰F= …… ⁰K
 30 ⁰ R= …… ⁰C = …… ⁰F = …… ⁰K

6. Exercise
 64 R= …. F= …. C= …. K
 50 F= …. C= …. R= …. K
 55 C= …. F= …. R= …. K
 318 K= …. C= …. F= …. R
C: R: F
5: 4: 9

7. Thermometers
Mercury thermometers
 Advantages
The expansion is regular
The scale range is long, -40 ⁰C to 350 ⁰ C
The color is shiny like silver so it is easy to see
Do not wet the walls of the thermometer
 Weakness:
Mercury is expensive
Cannot measure very low temperatures (below -40 ⁰ C)
If the tube is broken it will be dangerous, because mercury
is a toxic substance

8. Thermometers
Alcohol thermometer
 Advantages
Cheap alcohol prices
For a small increase in temperature, the alcohol undergoes
a larger volume change so that it can accurately measure
the temperature
Can measure very low temperatures (up to -1300 ⁰C)
 Weakness
Low boiling point (78 ⁰ C) so its use is limited
It is colorless, so it needs to be colored to make it visible
Wet glass walls

9. Thermal Expansion
 Bimetallic strip: two strips of different metals
fixed together.
 Thermostat: controller temperature of
bimetallic strip.

10. Measuring Heat Energy
 Heat capacity: amount of heat energy required
to raise the temperature of substance by 1 ⁰K or
1 ⁰C.

11. Example
 When a piece of copper is heated from 20⁰C to
70 ⁰C, the amount of heat needed is 9000 J. What
is the heat capacity of the piece of copper?

12. Example
When a piece of metal is heated from 30⁰C to 50 ⁰C,
the amount of heat needed is 4000 J. What is the
heat capacity of the piece of metal?

13. Measuring Heat Energy
 Specific heat capacity: amount of heat required
to raise the temperature of 1 kg of subtance by 1
⁰K or 1 ⁰C.

14. Example
 When a water (1 kg mass) is heated from 20⁰C
to 70 ⁰C, the specific heat capacity is 4200
J/kgC. What is amount of heat for each process?

15. Example
 When ethanol (0.5 kg mass) is heated from 20⁰C
to 50 ⁰C, the specific heat capacity is 230 J/kgC.
What is amount of heat for each process?

16. Heat Transfer

17. Heat Transfer
 Conduction: process by which heat is transmitted
through a medium from one partice to another.
Example: a piece of metal heats in a flame
 Convection: process by which heat is transmitted
from one place to another by movement of the
heated particles of gas or liquid. Example: sea
breeze and land breeze
 Radiation: heat transfer that does not require any
medium. Example: heat energy radiated by the sun
to earth