1. Investigation Two: Sink or Swim?

2. Density helps explain why heavy items such as the log or a boat are able to float.

3. Density: Sink or Float (1:43)

4. Density – the ratio of the mass (weight) of a material in proportion to its volume (size).

6. Volume – size, the amount of space occupied in three dimensions.

7. Volume (4:08)

8. Volume = Length x Width x Height
What is the volume for these objects?
1. L = 5 cm W = 5 cm H = 4 cm
2. L = 8 cm W = 3 cm H = 6 cm
3. L = 4 cm W = 9 cm H = 10 cm
4. L = 5 cm W = 8 cm H = 6 cm

9. Mass - the measure of the amount of matter (stuff) in an item, measured in grams.
Mass is similar to weight but different. Mass doesn’t change; weight does.

10. Density = mass/volume

11. Measuring Density (3:19)

12. Density = Mass/Volume What is the density for these objects?
1. M = 24 grams V = 3 cubic cm
2. M = 60 grams V = 15 cubic cm
3. M = 38 grams V = 2 cubic cm
4. M = 120 grams V = 10 cubic cm

13. If an object is less dense than water, it will float in water
If an object is less dense than water, it will float in water. If an object is denser than water, it will sink.

14. "I think as adults, we all know what floats and what doesn't float
"I think as adults, we all know what floats and what doesn't float. We all kinda can guess within a fairly close percentage what's gonna float.“
- David Letterman, February 28, 2002

16. System – a set of objects that are related in some way and can be isolated for study.

17. Large boats can float because they are a system made out of a dense hull and not very dense air which makes it less dense than water.

18. Salt water is denser than regular water therefore objects float better in it.

19. Buoyancy and the Titanic (8:35)

20. “Science in the Bathtub”

21. Archimedes – a Greek scientist, mathematician, and inventor.

22. Archimedes solved the riddle of King Hieron’s crown and the crooked goldsmith because silver is less dense than gold. In order to make the crown’s mass equal to the lump of gold’s mass the goldsmith had to use a larger volume of silver. The crown displaced/spilt a larger amount of water proving that the goldsmith had added silver and that the crown was not made out of pure gold.

24. Dr. Dad: Buoyancy (15:13)

25. Squidy!
How is squidy (a cartesian diver) like a submarine?

28. Review Questions
What is the ratio of mass in proportion to its volume known as?
What is volume?
What is the formula for density?
What will happen if an object is less dense than water?
What will happen is an object is more dense than water?
What is a system?
Why can large boats float?
Why do objects float better in salt water?

29. Review Questions Continued
Who was Archimedes?
How was the riddle of King Hieron’s crown solved?

30. The Way Things Work Video (VHS)

31. The End!

33. Variables Experiments Vocabulary
Capacity – the greatest amount of fluid a container can hold.

34. Buoyancy – the tendency of an object to sink or float in water.
Buoyant Force – the upward push of water on an object.

35. Buoyancy Explorer

36. Solid Density (g/cc) balsa ebony oak pine marble granite aluminum gold
iron
ice
tar
butter
0.125
1.22
0.75
0.425
1.918
2.7
19.3
7.87
0.917
1.02
0.86
Liquid
Density (g/cc)
water
olive oil
ethanol
corn syrup
honey
bromine
sea water
mercury 1
0.918
0.79
1.39
1.43
3.12
1.022
13.55

37. Displacement – the weight or volume of a fluid displaced by a floating object. As an object sinks it pushes water out of the way, displacing it.

41. Splash!

42. Independent Variable – the information you know before the experiment starts which is then charted on the x-axis (horizontal).

43. Dependent Variable – the information you find out by doing the experiment which is then charted on the y-axis (vertical).

44. Identifying Dependent & Independent Variables (3:08)

45. MythBusters Water Displacement