transmission of thermal energy

Question 1

heat (4)

Answer 1

• energy in transit
• flows from hotter body to colder
• symbol: Q
• S.I. unit: Joule, calorie

Question 2

temperature (5)

Answer 2

• measurement of amount of energy possessed by the molecules of a substance
• a degree of hotness
• can be used to predict direction of heat transfer
• symbol: T
• S.I. unit: Celsius, Kelvin

Question 3

ways of heat transfer (3)

Answer 3

• conduction
• convection
• radiation

Question 4

conduction (3)

Answer 4

direct thermal transfer (through atomic excitation??)

• occurs best in solids
• continues to be transferred until thermal equilibrium (same temp.)

Question 5

convection (4)

Answer 5

heat rises and thermal energy is carried by moving particles (in gas and liquid) in convection currents

• caused by density changes
• wind is caused by the cold air replacing rising hot air
• cooking appliances are heated from the bottom to make it heat the sinking cold fluid more efficiently

Question 6

radiation (3)

Answer 6

photons (light) carry energy and collide with other material

• dark and dull objects absorb more light than light and shiny objects
• works through the vacuum of space

Question 7

insulators (1)

Answer 7

slow transfer of heat (due to air pockets)

Question 8

conductors (1)

Answer 8

easily allow heat transfer (e.g: metal)

Question 9

thermos bottle (2)

Answer 9

• has double glass wall with vacuum between (prevents heat loss by conduction and convection)
• inside is lined with silver to reflect light (energy) and prevent heat loss

Question 10

greenhouse effect (4)

Answer 10

visible light passes through
→objects absorb light
→emit heat energy
→heat energy gets trapped