Fun with Density – Why is it important?

1. Fun with Density – Why is it important?

2. So what is density? • What is density? • Density is a measure of the amount of matter that occupies a given space. • What controls density of an object? • Mass • Volume • Measured in units of g/mL or g/cm3 • Does weight control density? • No!! • Mass and volume control it iron wood

3. Density of water • Important fact: • Density of water is 1 g/mL or 1 g/cm3 • Which will float in water - wood or iron? • Why? iron wood

4. Why is Density Important? • Density is one of the most important measurements in science. Being able to calculate density makes it possible to identify many unknown substances accurately. • For example, measuring density is how jewelers identify if something is real or fake gold. It makes it possible to determine if a ring is a valuable diamond, or just a cheap imitation. • Density is also used throughout industry as a way of separating materials that are made of different substances. • Differing densities of water, air, and earth materials all create interactions that effect daily life on Earth.

5. Importance of Density • Differences in density control… • Weather

6. Importance of Density • Differences in density control… • Weather • Ocean currents

7. Importance of Density • Differences in density control… • Weather • Ocean currents • Plate tectonics

8. Importance of Density • Differences in density control… • Weather • Ocean currents • Plate tectonics • And most importantly… lava lamps!

9. Density Formula • Density = mass (g) • volume (mL or cm3) • Mass - the amount of matter in an object • Volume - is the amount of space and object takes up

10. How to calculate • If density measured in g/mL or g/cm3 • First measure the…? (hint: find grams!) • Mass • Next, measure the…? • Volume • L x W x H or displacement method – which is? • Finally, divide mass by volume!! • Important! mL and cm3 are the same in the metric system. You can use either and be correct!

11. Examples of different densities • Aluminum 2.70g/mL • Cork 0.2 g/mL • Gold 19.3 g/cm3 • Ice 0.90 g/cm3 • Sugar 1.6 g/mL • Water 1.00 g/mL

12. Comparing densities • Wood in water? (does it matter what type?) • Ice in water? • Soda in water? • Marbles in water? • Oil in water? • What about something that “flinks?” • Does gas have density? Why is it so easy to walk through?

13. m V Density Formula mass D Density Volume

14. m g D V cm3 g cm3

15. Solving for Mass (m) m V V D V

16. Mass Formula V D m m V D

17. m V D g cm3 cm3 g

18. Solving for Volume (V) V D m D D

19. m D Volume Formula V

20. m D g V g cm3 cm3

21. You try one! • What is the density of vegetable oil if a beaker holds 275 mL of and the mass measures 190g? • 1. Write the formula: d = m v 2. Put in the values: d = 190 g 275 mL 3. Do the calculation.

22. Answer to last slide • d = 0.68 g or 0.69 g • mL cm3

23. Try it again! • Gold crowns that kings used to wear on their heads were very heavy. They usually weighed 20,000 grams. If the volume was 1,000 mL what was the density of the gold? • D = 20,000 g 1,000 mL d = 20 g/mL

24. Practice makes Perfect! • Different minerals can be identified by their different densities. What is the density of quartz if 38g put in a graduated cyl. with water at 5ml goes up to 15mL?

25. Last one! • Calculate the mass of alcohol in a jar that has a volume of 500 mL and the density of alcohol is 0.70 g mL D = m m = D x V v m = 0.70 g x 500mL mL

26. Density of Water: Sink or Float? • The density of water is 1 g/ml. This means that one gram of water occupies one milliliter of space. • If a substance has more matter than water in the same amount of space, it will be heavier. Therefore it will sink in water. So if it has a density of 2 g/ml, it sinks. What substances do you think have a density of more than one? • If a substance has less matter than water in the same amount of space, it will be lighter. So a density of .5 g/ml means that this substance with float! What would you predict has a density of less than one?