1. Chapter 11, Section 2 Floating and Sinking

2. What is Density? A comparison of how much matter there is in a certain amount of space (solids, liquids, gases) Density = Mass Volume Measured in g/cm 3 more dense less dense Table Talk: Why are these the units for density? Try It! A sample of liquid has a mass of 24g and a volume of 16 mL. What is its density? See Discovery Education, “Chemistry Basics: Matter,” clip “Density” (2:43) and clip“Calculating Density” (3:04)

3. Why do these layers separate? Which layer has the highest density? The lowest? Imagine their densities to be 3.0 g/cm,.30 g/cm and 30g/cm. Put these in order from greatest to least.

5. Changing Density This can explain why an object floats or sinks You can change the density of water by freezing it As ice, it is less dense, and floats…Why? Table Talk: How do you think submarines and fish sink to the bottom or float?

6. Let’s try some more problems…. Frank has a paper clip with a mass of 9g and a volume of 3 cm 3. What is its density? Which has great density, an eraser with a mass of 3 g and a volume of 1 cm 3, or an eraser with a mass of 2 g and a volume of 2 cm 3 ?

7. Quickwrite: Jake has a book, a ruler, and a balance scale. Write a few sentences on how Jake can find the density of the book with the tools he has.

8. Buoyancy The ability to float Water and other fluids exert an upward force called buoyant force It acts in the direction opposite gravity, so objects feel lighter Table Talk: If an object’s weight is greater than the buoyant force, what will happen?

9. Displacement Archimedes’ Principle The removal of something by something else that takes its place. The buoyant force acting on a submerged object is equal to the weight of the volume of fluid displaced by the object

11. Think about this: Air is a fluid. Why do balloons we blow up with our breath drop to the ground while balloons filled with helium gas float in the air? Why do these balloons, which to not contain helium, float? See BrainPop “Buoyancy” end