1. All objects experience a buoyant force when immersed in a fluid.
Standard 8
Density and Buoyancy
All objects experience a buoyant force when immersed in a fluid.

2. Anticipatory Set
Why do you think these two liquids weigh differently when they are the same amount?

3. Standard 8.8 (a-b) Students know density is mass per unit volume.
Students know how to calculate the density of substances (regular and irregular solids and liquids) from measurements of mass and volume.

4. LANGUAGE OF THE DISCIPLINE
Density: the mass-to-volume ratio of a substance
Volume: is the amount of space occupied by a 3-D object
Graduated Cylinder: container used to measure volume of a liquid.

5. Density
Which grouping is the most dense below?

6. Density Density is a physical property of matter
Density can be used to identify things
Example: No matter what size Aluminum is, or what shape, it will always be the same density
The ratio of mass to volume will always be the same

7. Measuring Volume Type of substance Tool/method Liquid
Graduated cylinder
Regular solid
Length * width * height
Irregular solid
Water displacement test
V (solid)= V (water & solid) – V (water)

8. Water displacement
Example: What is the volume of the dinosaur?
V (solid)= V (water & solid) – V (water)
= 0.8

9. Calculating Density

11. Check for Understanding
If you want to know the density and only know the mass what else do you need to find?
volume
What method should you use to find out the volume of an irregular solid?
Water displacement
How do you figure out the volume of a regular solid?
Length x width x height

12. Practice & HW Guided Practice: Independent Practice: HW:
Read through Guided instruction on page and highlight important information
Complete questions 1-4 on page 64
Raise hand for a stamp
Independent Practice:
Complete questions 1-4 on page 65
HW:
Worksheet

13. Why do some objects sink and some float?
Anticipatory Set
Why do some objects sink and some float?

14. Standard 8.8 (c-d)
Students know the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced.
Students know how to predict whether an object will float or sink.

15. LANGUAGE OF THE DISCIPLINE
Buoyant force: the upward force acting on a submerged object
Hydrometer: tube-like instrument used to determine density of liquid compared to water
Archimedes principal: a substance in a fluid is help up by a force equal to the weight of the displaced fluid
Naturally buoyant: an object that will not sink

16. Buoyant Force
is equal to the weight of the volume of fluid displaced by object.
So BIGGER VOLUME= BIGGER BUOYANT FORCE
Is measured in NEWTONS (since it is a force)
This is why you feel lighter in water

17. Buoyant Force Buoyant force occurs in fluids…
FLUIDS CAN BE GASES OR LIQUIDS
Example: Helium balloons rise because there is a greater buoyant force on it.

18. Archimedes’ principal
Pushed up by a force equal to weight of water displaced

19. Sink or Float
Sinking and floating all has to do with density and buoyant force
Naturally buoyant objects will not sink
This is why oil floats on water- it is less dense!

20. Sink or Float EXCEPTION: sometimes very dense objects can float.
Example: Steel Boats
They can float because of they way they are shaped so they do not displace as much water.
Hydrometer
It will sink deeper in LESS dense liquid
Float higher in MORE dense liquid

21. Check for Understanding
Page 69- Questions 2-5
Answers:
The plate would sink
The weight of the rock is greater than the weight of the water displaced, so the rock will sink
The distance it sinks in hydrometer indicated the density. The lower it sinks the less dense the liquid
A beach ball on top of water (since the beach ball is full of a fluid- AIR)

22. Practice & HW Guided Practice: Independent Practice: HW:
Read through Guided instruction on page and highlight important information
Complete the questions 6-8 on page 70
Raise hand for a stamp
Independent Practice:
Complete questions 1-4 on page 71
HW:
worksheet.