1. Density vs. Buoyancy What is Buoyancy? How is Buoyancy affected by Density? Applications of Buoyancy?

2. Buoyancy/Density Buoyancy and Density are very similar in that they both determine weather objects will sink or float HOWEVER… Buoyancy refers to the upward force that a fluid exerts that pushes against gravity Density refers to the property of matter that deals with it’s mass per unit of volume

3. Buoyancy Definition: Buoyancy is the tendency for objects to sink or float Buoyant force is the upward force exerted on an object that counters the force of gravity An object is said to “Float” when the buoyant force is stronger than the force of gravity

4. Buoyancy vs. Sinking Sinks – Gravity is Floats – Buoyancy is Neutral – Both stronger than the stronger than the forces cancel each force of buoyancy force of gravity so other out so the so the diver sinks the diver floats diver is static

5. Density & Buoyancy Obviously we can see that the density of the object floating is crucial, but what about the fluid exerting the buoyant force? Does it have an impact? What can you tell me about this picture and the densities, forces, and particles of both the fluid and object floating?

6. Class Demo We will take five different liquids from our Densities Centers Exercises a few classes ago… Syrup, Canola oil, Hand Soap, Motor Oil and Water Do you remember which was the most dense? least dense? If we hang a 200 g weight in the air from a spring scale, the spring scale will read 200 g (lets try it now) What will happen if we hang the same weight but this time it will be suspended within one of the three liquids? WHY? Will it be the same for all three liquids? WHY? LETS TRY IT OUT and record our results right now

7. Class Demo Copy this chart into your notes before we do the demo: What are your Predictions? Type of LiquidCalculated DensityWeight taken off of the 200 g Syrup1.36 g/ml Hand Soap1.15 g/ml Water1.00 g/ml Canola Oil0.93 g/ml Motor Oil0.88 g/ml

8. What Did We See? Based on what we just observed… Which Liquid was the most dense? Why? Which Liquid was the least dense? Why? Syrup… Because it took the most weight off when we submerged the 200 g mass in it Motor Oil… Because it took the least weight off when we submerged the 200 g mass

9. Which is More Dense?

10. So what can we say? So what is a simple statement that sums up what we know about the density of a liquid and the buoyant force it exerts on a n object The more dense = The higher the = The more weight the liquid buoyant force off the object exerted The less dense = The smaller the = The less weight the liquid buoyant force off the object exerted

11. The Big Idea!!! The amount of Buoyant force that is exerted by a fluid is dependent on the density… The more dense the fluid, the greater the buoyant force it will exert

12. A Little Chemistry Mercury vs. Gold… Which is more dense?

13. Textbook Reading Read pages 49 - 51 in the Science in Action 8 textbook that deal with the “Plimsoll Line”

14. Plimsoll Line

15. The Plimsoll Line on a cargo ship is put on each vessel to show how heavily it can be loaded in different types of water around the world You will need to explain how this line works on the test… so how does it work? Why are the lines where they are?

16. Your Assignment We are going to work through some questions together on your assignment that deal with the plimsoll line on cargo ships After that, you will have the rest of the period to work on the other questions on that worksheet Be sure to read the questions carefully Tackle the questions that you believe to be the hardest now, while you still have to opportunity to ask questions

17. Textbook Reading Use pages 59 - 69 in the Science Focus 8 Textbook to help you complete the worksheet. Use pages 49 - 51 in the Science in Action 8 Textbook to help you complete the worksheet.