1. Density A quantitative physical property of matter A quantitative physical property of matter Which is heavier: a 12 inch bar of gold or a pillow full of feathers? Which is heavier: a 12 inch bar of gold or a pillow full of feathers?

2. A 12 inch bar of gold weighs more than a pillow full of feathers even though the pillow takes up more space? Why? A 12 inch bar of gold weighs more than a pillow full of feathers even though the pillow takes up more space? Why? Gold is more dense. It has more matter per unit volume. Gold is more dense. It has more matter per unit volume.

3. is the amount of matter per unit volume of that matter. Density is the amount of matter per unit volume of that matter. Density (D) = Mass (m) / Volume (V ) If you know any two of the three variables (D, m, V), you can solve for the third. If you know any two of the three variables (D, m, V), you can solve for the third. m = DVV = m / D

4. Sample density question #1 If a rock has a mass of 49 g and occupies a volume of 7 cm 3, what is the density? If a rock has a mass of 49 g and occupies a volume of 7 cm 3, what is the density? D = m / V = 49 g / 7 cm 3 = 49 g / 7 cm 3 = 7.0 g/ cm 3 = 7.0 g/ cm 3

5. Solve these sample density questions 1. An object has a mass of 250 g and occupies a volume of 14.5 cm 3, what is the density? 2. A piece of wood occupies a volume of 46 cm 3 and it has a mass of 100 g. What is the density of the wood? 3. An unknown metal has a density of 2.6g/cm 3 and a mass of 15 g. How much volume does this piece of meal occupy. 4. A sample of a particular liquid has a density of 6.85 kg/L and it occupies a volume of 3.4 L. How much does this particular sample weigh?

6. Approximate Densities of Some Common Materials SubstanceDensity Kg/m 3 g/cm 3 Gold 19 300 19.3 Silver 10 500 10.5 Aluminum 2 700 2.7 Ice920.92 Wood (birch) 660.66 Distilled Water 1 000 1.0

7. Water is denser than ice! Why is this so important? Why is this so important? It means that ice floats in water instead of sinking. Think of the poor fish if this was not the case. It means that ice floats in water instead of sinking. Think of the poor fish if this was not the case. Why is ice less dense than water? Why is ice less dense than water? When water freezes, it expands which means that the same mass of water is spread over a greater volume. When water freezes, it expands which means that the same mass of water is spread over a greater volume.