1. Density

2. Vocabulary Proportional Inversely proportional Ratio

3. TEKS and TAKS The density concept will be tested on your TAKS Test in the Spring.

4. Goals and Expectations What is density? What is the density formula? How is density relevant to chemistry? What are the relationships between density & mass and density & volume and density & temperature? What is specific gravity?

5. Which box weighs more? These boxes are the same size and have the same volume. If each red ball weighs the same, which box weighs more?

6. Density is… The ratio of the mass of an object to its volume A physical property that depends on the composition of a substance, NOT the sample size

7. Density Equation Density (D) = Mass (m) Volume (v)

8. The Density Equation The density equation contains only three variables: density, mass and volume. quantityvariablecommon unit(s) density Dg/mL, g/L, g/cm 3 volume VmL, L, cm 3 mass mg

9. Understanding Density Mass = the amount of matter Volume = the amount of space Density is the relationship between the amount of matter and how much space that matter occupies.

10. Solve these problems Wood has a density of 5.53g/cm 3. What must the volume be of 33.3 g of wood? Sodium has a density of 1.95 g/cm 3. What is the volume of 56.2g of sodium?

11. Density of Liquids If several liquids of different densities are placed in a container, the liquids will be layered in order from smallest to largest going top to bottom.

12. Application Question Using the chart. If the liquids is the chart were placed in a test tube. How would they be layered from top to bottom? Let’s assume that all of the examples are liquids.

13. Which weighs more? One gram of gold One gram of water One gram of lead Trick Question! They all weigh the same!!

14. Density and Mass Density is proportional to the mass of the substance As one increases the other will also increase If two substances have the same volume, the substance with the greater mass will have the greater density.

15. Which substance will be denser? Fe Au volume = 10.00 cm 3 volume = 10.00 cm 3 mass = 78.74 gmass = 193.1g density = 7.874 g/cm 3 density = 19.31 g/cm 3 Fe Au

16. Which has a larger mass? One cm³ of gold (density = 19.3 g/cm³) One cm³ of water (density = 1.00 g/cm³) One cm³ of lead (density = 11.3 g/cm³) Think of the relationship between mass and density.

17. Let’s calculate to see if your predictions were accurate. One cm³ of gold (density = 19.3 g/cm³) One cm³ of water (density = 1.00 g/cm³) One cm³ of lead (density = 11.3 g/cm³) m = D x V m= 19.3 x 1 m = 19.3 g m = D x V m = 1.00 x 1 m = 1.00 g m = D x V m = 11.3 x 1 m = 11.3 g

18. Density and Volume Are inversely proportional As one increases the other will decrease. Therefore, if two substances have the same mass, the substance with the greater volume will have the smaller density. A large density means a small volume. A small density means a large volume.

19. Which has a larger volume? One gram of gold (density = 19.3 g/cm³) One gram of water (density = 1.00 g/cm³) One gram of lead (density = 11.3 g/cm³) Think of the relationship of density and volume.

20. Let’s see if your predictions were correct. One gram of gold (density = 19.3 g/cm³) One gram of water (density = 1.00 g/cm³) One gram of lead (density = 11.3 g/cm³) V = m/D = 1 / 19.3 = 1 / 19.3 = 0.052 cm³ = 0.052 cm³ V = m/D = 1 / 1 = 1 / 1 = 1.00 cm³ = 1.00 cm³ V = m/D = 1 / 11.3 = 1 / 11.3 = 0.0884 cm³ = 0.0884 cm³

21. Density vs. Temperature As the temperature rises, substances expand Expansion = an increase in volume Because of this, density is temperature dependent.

22. Look at the particles in each phase. Ask yourself, what happens to the volume as the temperature is increased? Which phase has the most volume? What is the relationship between volume and temperature Which phase is the most dense?

23. Water is an exception to the rule. Water is most dense at 4°C. Think about what temperature water freezes (0°C). So it is still a liquid at 4°C. In the solid phase of water the molecules are spread further apart than in the liquid phase. Remember: the closer the particles the more dense the phase. THIS IS WHY ICE FLOATS ON WATER

24. Determining the density of different objects. Geometric solid 1.weigh the object and record its mass 2.Measure its length, width, and height and use these measurements to determine the volume. 3.Calculate the density Irregularly shaped object 1.weigh the object and record its mass 2.Use the volume displacement method to determine its volume. 3.Calculate the density

25. Determining the density of different object. Liquid 1.Weigh a 10 mL graduated cylinder and record its mass. 2.Pour approximately 7mL(this is the volume) of the liquid into the graduated cylinder and weigh it. Record its mass. 3.Subtract the weight of the graduated cylinder from the weight of the graduated cylinder and the liquid (this is your mass). 4.Then calculate your density.