1. Density

2. What is density? Density is a comparison of how much matter there is in a certain amount of space.

3. What is density? Density is a comparison of how much matter there is in a certain amount of space. This definition combines 2 previously- learned definitions. “How much matter an object contains” is the definition of _________.

4. What is density? Density is a comparison of how much matter there is in a certain amount of space. “How much matter an object contains” is the definition of mass. “The amount of space an object takes up” is the definition of ________.

5. What is density? Density is a comparison of how much matter there is in a certain amount of space. “How much matter an object contains” is the definition of mass. “The amount of space an object takes up” is the definition of volume. So density combines the ideas of mass & volume.

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

7. Which one is more dense? Demonstration: People in a square How about this: Which square is more dense? Both have the same volume, but the one on the right has more mass. *

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

9. Which one is more dense? Now which one is more dense? * Both have the same mass, but the box on the left packs the mass in a smaller volume.

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

11. What is density? Density = mass OR mass ÷ volume. volume fsdgijolp[lp;jkrtersrtyup[;’,mn rtea546eszf89puhb jp[] Units for density: g. or g. cm 3 mL Why are these the units for density? If D= m and m is measured in grams, then g is on top. v If v is on the bottom & v is measured in cm 3, then cm 3 goes on bottom. ALWAYS REMEMBER UNITS!

12. 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? First step: Write the formula. Density= mass or simply D = m volume v

13. 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? First step: Write the formula. Density= mass or simply D = m volume v Second step: Plug in the numbers. D = 9g. 3cm 3

14. 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? First step: Write the formula. Density= mass or simply D = m volume v Second step: Plug in the numbers. D = 9g. 3cm 3 Third step: Do the math. 9÷ 3 = 3.

15. Let’s try a density problem together Dave has a paper clip. It has a mass of 9g and a volume of 3cm 3. What is its density? First step: Write the formula. Density= mass or simply D = m volume v Second step: Plug in the numbers. D = 9g. 3cm 3 Third step: Do the math. 9÷ 3 = 3. Fourth step: Write the correct units. 3 g/cm 3

16. Let’s try a density problem together Ernestine has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density?

17. Let’s try a density problem together Ernestine has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density? D = m v

18. Let’s try a density problem together Ernestine has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density? D = m = 3g v 1cm 3

19. Let’s try a density problem together Ernestine has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density? D = m = 3g = 3 g/cm 3 v 1cm 3

20. Work on these problems with your neighbor. 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 pen?

21. Work on these problems with your neighbor. 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 pen? D = m = 8g = 4g/cm 3 v 2cm 3

22. 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?

23. 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? D = m = 6g = 2g/cm 3 v 3cm 3

24. Now, try these on your own. Alicia has a watch. It has a mass of 4g and a volume of 2cm 3. What is the density of the watch? Mr. Barrett has a wallet. It has a mass of 15g and a volume of 5cm 3. What is the density of the wallet?

25. Now, try these on your own. Alicia has a watch. It has a mass of 4g and a volume of 2cm 3. What is the density of the watch? D = m = 4g = 2g/cm 3 v 2cm 3 Mr. Barrett has a wallet. It has a mass of 15g and a volume of 5cm 3. What is the density of the wallet?

26. Now, try these on your own. Alicia has a watch. It has a mass of 4g and a volume of 2cm 3. What is the density of the watch? D = m = 4g = 2g/cm 3 v 2cm 3 Mr. Barrett has a wallet. It has a mass of 15g and a volume of 5cm 3. What is the density of the wallet? D = m = 15g = 3g/cm 3 v 5 cm 3

27. Instead of telling you the volume, a question might show you some information and you will have to come up with the correct volume on your own. You would then use that volume to calculate the density. There are 3 ways to find the volume of a sub- stance depending on if it is a liquid, a regular solid, or an irregular solid.

28. If the substance is a liquid, you must read the meniscus of a graduated cylinder. Example: The mass of the liquid in this graduated cylinder is 219 g. What is its density?

29. If the substance is a liquid, you must read the meniscus of a graduated cylinder. Example: The mass of the liquid in this graduated cylinder is 219 g. What is its density? First write equation: D= m/v. Then plug in data: m = 219g and diagram shows v = 73ml. Then do the math. 219g ÷ 73ml = 3g/ml.

30. Second example: The mass of this liquid is 36g. What is its density?

31. Second example: The mass of this liquid is 36g. What is its density? D = m = 36g v 18ml 36 ÷ 18 = 2 Density = 2 g/ml

32. Do this one with a partner. This liquid has a mass of 70g. What is its density?

33. Do this one with a partner. This liquid has a mass of 70g. What is its density? D = m = 70g v 35ml 70 ÷ 35 = 2 Density = 2 g/ml

34. If the substance is a regular solid, you must calculate the volume using V=length * width * height. Then plug that answer into D = m/v.

35. First example: What is the density of the solid below if its mass is 150g?

36. First example: What is the density of the solid below if its mass is 150g? Measurements below are in cm. First calculate volume. 2cm* 5cm* 3cm = 30cm 3.

37. First example: What is the density of the solid below if its mass is 150g? Measurements below are in cm. First calculate volume. 2cm* 5cm* 3cm = 30cm 3. Then plug in the 30cm 3 into the density formula. D= m = 150g v 30cm 3 150 ÷ 30 = 5, so density = 5g/cm 3.

38. Next example: The mass is 48g. What is the density?

39. Next example: The mass is 48g. What is the density? First solve for volume. V = l*w*h V = 2cm * 3cm * 4cm = 24cm 3

40. Next example: The mass is 48g. What is the density? First solve for volume. V = l*w*h V = 2cm * 3cm * 4cm = 24cm 3 Then solve for density. D = 48g ÷ 24 cm 3 = 2g/cm 3

41. Now try this one with your partner. The mass is 72g. What is the density of this box?

42. Now try this one with your partner. The mass is 72g. What is the density of this box? V = 8cm * 1cm *1cm = 8cm 3. D = 72g ÷ 8cm 3 = 9g/cm 3

43. To get the density of an irregular solid, measure the volume of water in a graduated cylinder before and after you drop in the solid. Subtract the 2 measurements to get the solid’s volume. Plug the volume into the formula for density. 23 ml before 30 ml after Rock’s mass = 35g

44. To get the density of an irregular solid, measure the volume of water in a graduated cylinder before and after you drop in the solid. Subtract the 2 measurements to get the solid’s volume. Plug the volume into the formula for density. 23 ml before 30 ml after First get Volume: 30ml - 23ml = 7ml Rock’s mass = 35g

45. To get the density of an irregular solid, measure the volume of water in a graduated cylinder before and after you drop in the solid. Subtract the 2 measurements to get the solid’s volume. Plug the volume into the formula for density. 23 ml before 30 ml after First get Volume: 30ml - 23ml = 7ml Then get density: D = m = 35g = 5g/ml v 7ml Rock’s mass = 35g

46. What is the density if the rock’s mass is 80g? 22 ml before 32 ml after Rock’s mass = 80g

47. What is the density if the rock’s mass is 80g? 22 ml before 32 ml after First get Volume: 32ml - 22ml = 10ml Then get density: D = m = 80g = 8g/ml v 10ml Rock’s mass = 80g

48. What is the density if the rock’s mass is 45g? 27 ml before 32 ml after Rock’s mass = 45g

49. What is the density if the rock’s mass is 45g? 27 ml before 32 ml after First get Volume: 32ml - 27ml = 5ml Then get density: D = m = 45g = 9g/ml v 5ml Rock’s mass = 45g

50. What is the height of an object if the volume is 700 cm 3 ? 10cm H

51. What is the height of an object if the volume is 700 cm 3 ? 10cm H First write formula: V = l * w * h Then plug in: 700cm 3 = 10cm * 10cm * h multiply: 700cm 3 = 100 cm 2 *h Solve for H: 700cm 3 = 100 cm 2 *h 100cm 2 100 cm 2 7 cm = h

52. What is the height of an object if the volume is 720 cm 3 ? 8cm H 9cm

53. What is the height of an object if the volume is 720 cm 3 ? 8cm H 9cm First write formula: V = l * w * h Then plug in: 720cm 3 = 8cm * 9cm * h multiply: 720cm 3 = 72 cm 2 *h Solve for H: 720cm 3 = 72 cm 2 *h 72cm 2 72 cm 2 10 cm = h

54. Do this one with a partner. What is the length of an object if the volume is 240 cm 3 ? L 6 cm 5cm

55. Do this one with a partner. What is the length of an object if the volume is 240 cm 3 ? L 6 cm 5cm First write formula: V = l * w * h Then plug in: 240cm 3 = L * 5cm * 6cm multiply: 240cm 3 = L * 30cm 2 Solve for H: 240cm 3 = 30 cm 2 *L 30cm 2 30 cm 2 8 cm = L

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