1. Unit 3 lec 7- Density and Convection
Image credit:
Wikimedia Commons; (CC BY-SA 3.0)

2. Density is a measure of how tightly packed the molecules of a substance are. Imagine that each  is a molecule. Label the following boxes in order from least dense (1) to most dense (3)

3. One thing that we know about density is that substances,
that are less dense will float in substances that are more dense.
What can you tell us about the density of water, alcohol, & ice cubes?
Ice is (more/less) dense than liquid water? (circle one)
Ice is (more/less) dense than rubbing alcohol (circle one)
Liquid water is (more/less) dense that rubbing alcohol? (circle one)
Place in order of increasing density:
______________ < _________________ < ________________

4. Density is a derived unit (from mass and volume)
To measure density we use an equation
Density = Mass
Volume
D = g/ml or D = g/cm3
Density is a derived unit (from mass and volume)
Density is an intensive property (independent of amount)

5. Examples:
An object has a mass of 5.0 g and occupies a volume of 15ml, what is its density?
D= m v
D = 5g
15ml
D= 1 g/ml 3
D= .33 g/ml

6. 2. Are gases more or less dense than liquids/solids at room temperature? Based on your everyday experiences, how do you know?

7. Conduction Review Exchange of heat by direct contact
Air warmed on the pavement
Making popcorn on the stove
Meat on a frying pan
The teacher will state that the picture represents conduction: the pancakes are receiving direct heat from the skillet.
Image credit:
Alyss, Flickr; (CC BY-NC-SA 2.0)

8. Convection
Convection: Transfer of heat in fluids (liquids and gases) through rising and falling currents
Warm air rises causing cold air to come in= wind
Water molecules rising and falling when water boils in a pot
The teacher can show this slide to assist the students will completing the chart in slide 7.

9. Convection- model convection in a lava lamp https://www. youtube
The teacher will explain the mobility of the particles in the transfer of heat. Hot water rises and cold water sinks—or in the case of lava lamps, the hot “lava” rises from the bottom and falls from the top as it cools.
Image Credit:
PacoScott, Flickr; (CC BY-NC 2.0)

10. Lava Lamp

11. How do they make lava lamps (start at 1:50)

14. Explore Activity
Can you explain what happened in the explore activity now?