IDUSCIENCE L07 Convection

Convection

Warm up

Questions from previous lesson

Multiple Choice

...............is a form of energy that transfers from higher temperature object to the lower temperature object.

• Light

• Heat

• Sound

Multiple Choice

Conduction requires

• Electricity

• the electromagnetic spectrum and particles

• air or water flow

• direct contact

Multiple Choice

Which direction is heat flowing in the picture?

• from the hand to the ice
• from the ice to the hand
• heat is not being transferred
• there is no way to tell

Recall that liquids and gases are fluids

Describe convection currents formed by hot or cold objects.

Use ideas about particles to describe how heat is tranferred in fluids.

​Objectives

Keywords

convection

fluid

dense

density

How does heat energy travel
through liquids and gases?

• Liquids and gases are fluids.

• Heat energy does not travel through fluids very well by conduction because of the arrangement of particles.

• It can travel by convection.

​Fluids

• Density is mass per unit volume

• The density of a substance depends on how far apart its particles are.

Density

​Density

• Objects will sink (move downwards) if they are more dense than a
  medium.

• Objects will suspend (stay in place) if they are the same density as the
  medium.

• Objects will float (move up) if they are less dense than the medium.

​What happens if there are density differences in a liquid?

​Convection

Demonstration 2

Hot air rising

• Plays a huge part in the weather.

• Some parts of the earth are warmed more than the others by the sun.

• Warm places on earth heat the air above them, and convection currents form.

• We feel these currents as wind.

​Convection in everyday life

Convection in everday life

Some birds use rising columns of warm air to
keep them in the air.

Convection currents can also form when part of a fluid is colder than its surroundings

​Convection in everyday life

Multiple Choice

Convection can occur in

• Only solids

• Only liquids

• Only gases

• Fluids (Liquids and gases)

Multiple Choice

Which object has a greater density?

• Left

• Middle

• Right

• They are all equal

Multiple Choice

Why is the air over the water sinking?

• It is less dense than the air around it

• It is more dense than the air around it

• The pressure from the atmosphere pushes it

Reorder

Reorder the following

• Air is heated

• Particles move further apart

• It becomes less dense

• It rises

1

2

3

4

• 1
• 2
• 3
• 4