1. Is the buoyant force greater than,
less than, or equal to, the weight of
the objects below?
Fig. 1
Fig. 2
Fig. 3Less Than
Greater Than
Equal To

2. ReviewReview
 Density
 Buoyancy

Liquids

Gases

3. Density AnomalyDensity Anomaly
 Hydrogen bond - when
the (+) side of an H2O
molecule attracts the (-)
side of another H2O
molecule

4. Liquid HLiquid H22OO Hydrogen
bond

5. Density AnomalyDensity Anomaly
 As H2O cools off, the
hydrogen bonds become
stronger
 “ice” crystals form
Regular
repeating
arrangement
of atoms

6. Solid
H2O
“ice”

7. Water Ice

9. Density AnomalyDensity Anomaly
 As ice forms, its volume
increases
 But its mass stays the
same

10. Density AnomalyDensity Anomaly
 When the volume goes up,
but the mass stays the
same, the density goes
down

11. Why does ice float?Why does ice float?
 Solid H2O (ice) is less
dense than liquid H2O
(water)
 Ice = .9 g/cm3
 Water = 1 g/cm3

18. Lake Superior
froze over
completely in 1996