1. We all know that a ton of bricks has the same mass as a ton of feathers, but How can you tell the difference between the two? Write your answers on the white board.

2. Which one is more dense? Demonstration: People in a square Demonstration: People in a square How about this: Which square is more dense? How about this: Which square is more dense?

3. Which one is more dense? Now which one is more dense? Now which one is more dense?

4. – Density: is the mass of an object or substance compared with its volume – Density is a physical property –Density is calculated using the following formula: **The density of water is 1.0 g/ml. Anything with a density less than 1.0 g/ml will float in water. Anything with a density greater than 1.0 g/ml will sink.

5. What is density? Density = mass OR mass ÷ volume. Density = mass OR mass ÷ volume. volume volume Units for density: g OR g. Units for density: g OR g. cm 3 mL cm 3 mL Why are these the units for density? Why are these the units for density? ALWAYS REMEMBER UNITS!

6. Let’s try a density problem together Frank has a paper clip. It has a mass of 9g and a volume of 3cm 3. What is its density? Frank has a paper clip. It has a mass of 9g and a volume of 3cm 3. What is its density? Frank also has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density? Frank also has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density?

7. Work on these problems with your neighbor. Jack has a rock. The rock has a mass of 6g and a volume of 3cm 3. What is the density of the rock? Jack has a rock. The rock has a mass of 6g and a volume of 3cm 3. What is the density of the rock? Jill has a gel pen. The gel pen has a mass of 8g and a volume of 2cm 3. What is the density of the rock? Jill has a gel pen. The gel pen has a mass of 8g and a volume of 2cm 3. What is the density of the rock?

8. Sink or float? On Whiteboards Water’s density=1.0 g/ml 1. Air Density=.0013 g/cm 3 Density=.0013 g/cm 3 Sink or Float? Sink or Float? 2. Bricks Density= 1.84 g/cm 3 Density= 1.84 g/cm 3 Sink or Float? Sink or Float? 3. Oak wood Density= 0.7 g/cm 3 Density= 0.7 g/cm 3 Sink or Float? Sink or Float? 4. Silver Density= 10.50 g/cm 3 Density= 10.50 g/cm 3 Sink or Float? Sink or Float?

9. Buoyancy Buoyancy: the tendency to float when placed in a fluid Buoyancy: the tendency to float when placed in a fluid Buoyancy depends on the density of an object Buoyancy depends on the density of an object –If the density of an object is more than the density of water than it will sink Buoyancy is the upward force of fluid Buoyancy is the upward force of fluid An object is buoyant if it floats An object is buoyant if it floats Example: boats float Example: boats float rocks sink

10. ExamplesFloats A heavy ship can float on water because it is not solid through out. Instead, the ship has many hollow areas which results in the ship having a large volume. A heavy ship can float on water because it is not solid through out. Instead, the ship has many hollow areas which results in the ship having a large volume.Sinks A rock sinks in water because it is solid throughout. The density of the rock is more than the density of water, so it sinks. A rock sinks in water because it is solid throughout. The density of the rock is more than the density of water, so it sinks.

11. Density and Buoyancy ISN pg 19 Density Density – the amount of matter in a certain volume. – Use the formula: Density=Mass Volume Volume – Density of water=1.0 g/ml – Buoyancy – an object is buoyant if it floats – Buoyancy depends on density – An object is buoyant and will float if its density is less than the density of water (1.0 g/ml) – Examples that float: a cork, boats, and pinewood – Examples that sink: cement block, and iron

12. Tuesday, March 29, 2011 Please take out your Density practice homework from yesterday and pen or pencil to correct Please take out your Density practice homework from yesterday and pen or pencil to correct

13. Super Scientist Question of the Day Jake has a book, a ruler, and a balance. Jake has a book, a ruler, and a balance. How can Jake find the density of the book with the tools he has? How can Jake find the density of the book with the tools he has?