1. Density

2. Which weighs more? Which one of these weighs more??? A kg of bricks or a kg of feathers? Both of the objects are 1 kg… so they both weight the same. So why do we want to say bricks???? A kg of bricks may not weigh more, but it does have a higher density!!!

3. What is density? Density is the amount of mass an object has per unit of volume. How tightly or loosely packed the molecules in a substance are. All substances have densities, solids liquids and gases.

4. Differences in Densities Two objects with the same volume and different masses will have different densities. Take a look at the picture below and decide which object is more dense.

5. Differences in Densities Which one of these boxes is more dense??? Box B… Why? The same amount of matter (mass) is packed into a smaller space (volume)

6. What about liquids? Differences in densities can be seen in liquids to. When liquids of different densities are mixed together, the denser liquids will sink below the less dense liquids. Oil, least dense. Water. Syrup, most dense.

7. Another Example

8. What about Solids IN Liquids? If a solid is placed in a liquid it will either sink or float. Solids with a higher density than the liquid they’re placed in will sink. Solids with a lower density than the liquid they’re placed in will float.

9. Examples? Wood will float in water, so wood is less dense than water. A block of lead will sink in water, so lead is more dense than water. Cool fact… lead is less dense than mercury. So….

10. Lead will FLOAT in Mercury!

11. Ice in Water? Which has a higher density? Ice or water? Ice floats in water, so water must have the higher density… but why? Water EXPANDS as it freezes!!

12. To calculate Density: Equation: Mass (g): – Triple Beam Balance Volume (cm 3 ): – Measure (L x W x H) – Water Displacement (Graduated Cylinder)

13. Density’s Label Mass is always measured in grams Volume of Liquids and Gases are measured in milliliters Volumes of Solids are measured in cm 3

14. Density’s Label Density of Liquids or Gases: - g/ml Density of Solids: - g/cm 3

15. Example 1 What is the Density of the following Solid Object? L = 4.0 cm W = 2.0 cm H = 2.0 cm MASS 160.0 g

16. Answer (Example #1) Mass = 160.0 g Volume = L x W x H V = (2.0 cm) x (2.0 cm) (4.0 cm) x V = 16.0 cm 3 D = 16.0 cm 3 160.0 g = 10.0 g/cm 3

17. Size and Density How will an object’s density change if it is cut into two or more pieces? Mass = 16.0 g Volume = 4.0 cm 3 Density = ________ = 1g particle = 1cm 3 Mass = 4.0 g Volume = 1.0 cm 3 Density = ________ WHICH HAS A GREATER DENSITY? THEY ARE THE SAME! 4.0 g/cm 3

18. Factors Affecting Density Temperature – When temperature increases, objects expand, causing the density to decrease. Pressure – When pressure increases, objects compress, causing the density to increase.

19. Temperature and Density Heat Added Object Expands Temp Density RELATIONSHIP: As temperature INCREASES, density DECREASES Indirect

20. Pressure and Density Pressure Added Object Compresses Press Density RELATIONSHIP: As pressure INCREASES, density INCREASES Direct