Download lesson-5-convection

Lesson Starter
1. What is the process called when heat travels through
solids?
2. Describe what happens to the particles during this
process
3. Which solids are the best at this process?
4. Do you THINK that heat can travel through other
states of matter? Why?
Learning Intention
To understand how heat travels
through liquids and gases
Discuss
Explain how radiators heat a room
HINT- think of the particles
Warm air
particles out
into the room
Cold air
particles in
A radiator works by heating up the gases in the air around it.
The gas particles vibrate and start to move further apart making
them less dense.
The less dense gas will now rise and the cooler gas will move in and
take its place.
Convection
• Liquids and gases- poor
conductors
• Transfer energy by convection
• Particle arrangement
• Particles rise and fall
• Can’t take place in solids- why?
• Particles gain energy and spread
out making them less densethey rise
• Lose energy, cools and fall
Convection currents in gases
1. Cut out the spiral and tie on a
piece of thread.
2. Hang it above a Bunsen burner
3. Watch and describe what
happens.
Convection currents in gases
Hot, less dense air rising
catches the paper spiral
and starts to turn it
around.
Convection experiment
1. Place about 300 mls of water into a
beaker and place on a tripod stand.
2. Start to heat the water with a bunsen
burner (blue flame).
3. Carefully drop the coloured crystal
into the beaker so that it is seating at
the bottom of the beaker. Watch
what happens.
Convection experiment
The less dense liquid will now rise and the cooler liquid or will
move in and take its place. As a result of these movements, a
convection current will be set up in the substance.
Convection currents in liquids
Convection currents can
be found when liquids
are heated for cooking.
Convection (copy)
• When substances are heated, the particles vibrate more vigorously,
and as a result, spread out more.
• Because the particles are not so tightly packed anymore, the heated
substance becomes slightly less dense and therefore lighter.
• The less dense liquid or gas will now rise (taking the heat with them)
and the cooler liquid or gas will move in and take its place.
Textbook
• Page 109 in starting science 1 (purple)
• Read the information and answer the
questions at the bottom of the page