Thermal Energy Examples

Question 1

Holding a marshmallow in a flame is what type of heat transfer?
convection conduction radiation

Answer 1

conduction
why: The marshmallow is INSIDE the flame, directly touching it. This makes it conduction. If it was outside the flame and not touching it, that would be radiation.

Question 2

Heater on 1st floor of a building heating the 2nd floor of a building:
convection conduction radiation

Answer 2

convection
why: the heated air rises through vents, doorsways, and the floor. Heat transferring through moving air is convection.

Question 3

Placing pot on hot stove in order to boil water is example of
convection conduction radiation

Answer 3

conduction
why: While boiling water itself is convection, the heat transferred from the hot stove to the pot is conduction because the pot is touching the stove.

Question 4

a lizard warming its belly on a warm rock
convection conduction radiation

Answer 4

conduction
why: because the belly is directly touching the heat source of the warm stone, direct contact = conduction

Question 5

rising of a hot air balloon
convection conduction radiation

Answer 5

convection
why: air is heated by a flame, that heated air rises while colder air sinks. The cold air heats and rises, and the cycle repeats. Heat being transferred through air is convection.

Question 5

ice melting in your hand
convection conduction radiation

Answer 5

conduction
why: the ice is melting as a direct result of physically touching your warm hand. direct contact = conduction.

Question 6

warming your hands by placing them on a warm cup of tea
convection conduction radiation

Answer 6

conduction
While the originating heat source is the tea, that tea has warmed the cup. Your hands are directly touching the cup itself. Because of the direct contact with a conductive source, it’s conduction.

Question 7

water boiling in a pot on a stove
convection conduction radiation

Answer 7

convection
why: the stovetop is heating the pot by conduction, the act of the water boiling is itself convection (heat transfer moving through liquid)

Question 8

roasting a marshallow over a fire (not inside a flame)
convection conduction radiation

Answer 8

convection and radiation!
why: because the marshallow is not inside the flame directly touching it - it is not conduction. The marshmallow is roasting by radiation from the fire but also by heated air rising from the fire. The amount of heat transfer by convection is largely related to where you are holding the marshmallow (over vs side)

Question 9

warming yourself by a campfire
convection conduction radiation

Answer 9

radiation
why: because you are not in direct contact with the flames (hopefully), and you are not sitting directly over the fire where you are heated by rising air (convection), you are being heated by the radiation from the fire when you sit off to the side.

Question 10

cooking food in a microwave
convection conduction radiation

Answer 10

radiation
why: microwaves cook food by emitting a type of wave through the air to the food by radiation. There is no direct contact with the heat source (conduction), and there is no heated air moving (convection).

Question 11

a snowman melting in the midday sun

Answer 11

radiation
why: because it’s the sun’s rays traveling by radiation heating the snowman causing the snow to melt.