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# Catalyst

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1. Catalyst • If I have a can of coke and I put it in a bowl of water, will it sink or float? What about a can of diet coke? • Convert 3 mL to ounces • A scientist wants to test his hypothesis: If I use fertilizer on my lawn every day then my grass will grow taller because it’s receiving more nutrients • Write a scientific question and identify the independent variable, dependent variable, control and constants

2. Objectives • SWBAT calculate the density of objects by using measured mass and volume • SWBAT compare densities of various objects

3. Agenda • Teacher demos • Density Lecture • Density Essential Lab Activity • Calculate Densities Measured • Precision vs Accuracy • Lab Results and Conclusions

4. Which floats, Coke or diet Coke?

5. Apply it to real life: What makes Coke different from diet Coke? More sugar Less sugar

6. So what can we conclude about density? More dense = sink Less dense = float

7. Definition of Density • Density: the amount of matter per unit of space of an object But what does that really mean?

8. Compare Thing 1 and Thing 2 Which of these has more matter? Which has more space? So which one is the most dense? Thing 1 Thing 2

9. Compare Thing 1 and Thing 2 Matter/ Matter/ Space Space Less dense Thing 1 Thing 2 More dense

10. Definition of Density • Density: the amount of matter per unit of space of an object But what does that really mean? • How compact or packed together the matter is in the space of an object. • This is a property of matter that does not change with the amount of the object

11. Compare Thing 3 and Thing 4 Which of these has more matter? Which has more space? So which one is the most dense? More dense Thing 4 Thing 3 Less dense

12. Liquid Layers – Check it out! • Which liquid has the highest density? • Which liquid has the lowest density? • Which liquid has the middle density? Can you tell the density of something by looking at it?

13. Definition of Density • Density: the amount of matterper unit of space of an object Matter:per:Space: Mass Volume

14. Formula for Density D = m = mass = g or g V volume mL cm3 Tools: scale and ruler/graduated cylinder

15. Density Lab and Sample Calculations • Rotate around the room and visit each of the 5 Stations At each station, you will find instructions on what to do along with some questions. • After taking all necessary measurements and answering the questions at the station, rotate to the next station. • Note: Do not calculate the density, we will do that as a class • Once you have visited every station, return to your seat.

16. Density Lab and Sample Calculations • What is your data obtained for water? • What is your volume? • What is the mass? • What is the density of water?

17. Density Lab and Sample Calculations What is your density for the water?

18. Precision vs Accuracy Precision = how close measurements are to each other Accuracy =how close the measurements are to the “true” value

19. Density Lab and Sample Calculations Now calculate the densities for each of the stations in your lab composition book

20. Density Lab Observation Questions Answer the following questions in your lab notebook: • What is the density determined for your water sample? • What could you do to improve the accuracy of your measurements? • How does the density of the weight compare to the density of water? Which is denser? • Nickel (metal) has a density of 8.91 g/mL. Compare this to the density of the nickel coin you calculated. Is the nickel coin made of pure nickel (metal)?

21. Density Lab Conclusion Questions Answer the following questions in your lab notebook: • When you use the terms heavier or lighter to compare different objects with the same volume, what property of the objects are you actually comparing? • Would you expect the densities of various fruit juices in the same container to all be the same? Explain. • How can the concept of density be used to differentiate between a genuine diamond and an imitation diamond? • The density of aluminum is 2.70 g/cm3. What volume will 13.5 grams of aluminum occupy? HINT, use unit conversion!

22. Homework # 2: Due Next Class Homework can also be downloaded from the class website • What is the density of 10 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 45 mL? • What is the density if 50 g of a metal occupies a volume of 5 cm3? • If you were trying to test whether Advil or Tylenol reduced fevers more, write a problem statement, hypothesis and variables for an experiment you could perform.

23. Problem 1 Osmium is a very dense metal. What is its density if 50.00 g of the metal occupies a volume of 2.22 cm3? lecturePLUS Timberlake

24. Solution D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 = 22.5 g/cm3 lecturePLUS Timberlake

25. Problem What is the density of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 33 mL 25 mL lecturePLUS Timberlake

26. Solution Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL D = mass = 48 g = volume 8 mL = 6 g/mL lecturePLUS Timberlake