Name Date Period HS Chemistry POGIL Activity Topic: Density

What is density?

Why? You’ve no doubt heard about density in science classes or in your everyday life. But what does it really mean for one object to be denser than another?

1. How many dots are in the following cubes?

A1

A2

B1

B2 2. Based upon Model 1, what is mass?

3. What can you infer about how much mass each dot represents?

4. As volume increases on the graph’s X-Axis, what changes about each cube? What evidence from Model 1 supports your thoughts?

B1

B2

A2

A1

Material B

Material A

Mass and VolumeModel 1:

5. Use the following data to calculate the volume for each of the cubes. Remember that the formula for

calculating volume for a cube is length x width x height.

Object Length Width Height Volume A1 2 cm 2 cm 2 cm A2 3.174 cm 3.174 cm 3.174 cm B1 2 cm 2 cm 2 cm B2 3.174 cm 3.174 cm 3.174 cm

6. According to your calculations, what would be the units for volume? Why?

7. With your group members, create your own definition of volume.

8. What is similar about objects A1 and A2?

9. What is similar about objects B1 and B2?

10. Based upon your prior knowledge for density and the ideas you summarized in questions 8 and 9, create a definition for density with your group members.

SUMMARIZING QUESTIONS Instructions: Discuss these questions with your group. Write down your ideas. Leave space to add additional ideas or thoughts you gain from the Summarizing Discussion.

1. Which of the following objects is denser? Which is less dense?

Explain why

2. On the graph below, a line has been added to show the density of water. Based upon its density, explain which objects you think will sink and which will float and why.

3. Oil floats on top of water. Explain why and draw a picture (using dots like in Model 1) to show why this

is the case.

How can you calculate density?

Why? How can you calculate density using the mass and volume of an object?

Model 2: Density Calculations Object Mass Volume Density

Object C

8 grams 5.33 mL 1.5 grams/mL

Object D

20 grams 13.33 mL 1.5 grams/mL

4. Evaluate Model 2. What is the same between Object C and Object D? Why is this (based on their pictures?

Water

5. How is density calculated using the mass and volume values?

6. Come up with a formula for calculating density (based on the numbers in Model 2).

7. Do you think that objects C and D are made out of the same or different material? Explain using evidence from Model 2.

8. Complete the following table using data from the graph presented in Model 1, your volume calculations in question 5, and your inferences from Model 2.

Object Mass Volume Density

9. Calculate density for the following objects: a. A 114 gram box that has the dimensions: length =3 cm, width = 3 cm, height = 7cm

b. A rock which has a mass of 60 grams and a volume of 20 mL

c. An unknown liquid with a mass of 10 grams and a volume of 15 mL

More Practice Density Problems

Solve the following problems showing all your work including equations and units.

1. Calculate the mass of a liquid with a density of 3.2 g/mL and a volume of 25 mL. (answer = 80 g)

2. An irregular object with a mass of 18 kg displaces 2.5 L of water when placed in a large overflow container. Calculate the density of the object. (answer = 7.2 kg/L or 7.2 g/mL or 7.2 g/cm3)

3. A graduated cylinder has a mass of 80 g when empty. When 20 mL of water is added, the graduated cylinder has a mass of 100 g. If a stone is added to the graduated cylinder, the water level rises to 45 mL and the total mass is now 156 g. What is the density of the stone? (answer = 2.24 g/mL or 2.24 g/cm3)

Chemistry: Density Problems similar to those found on the next test.

For each problem below, write the equation and show your work. Always use units and box in your final answer.

1. The density of silver (Ag) is 10.5 g/cm3. Find the mass of Ag that occupies 965 cm3 of space.

2. A 2.75 kg sample of a substance occupies a volume of 250.0 cm3. Find its density in g/cm3.

3. Under certain conditions, oxygen gas (O2) has a density of 0.00134 g/mL. Find the volume occupied by 250.0 g of O2

under the same conditions.

4. Find the volume that 35.2 g of carbon tetrachloride (CCl4) will occupy if it has a density of 1.60 g/mL.

5. The density of ethanol is 0.789 g/mL. Find the mass of a sample of ethanol that has a volume of 150.0 mL.

6. 30.0 g of each of the following acids are needed. Find the volume of each that must be measured out in a graduated cylinder.

A. hydrochloric acid (HCl), density = 1.164 g/mL

B. sulfuric acid (H2SO4), density = 1.834 g/mL

C. nitric acid (HNO3), density = 1.251 g/mL

7. A rectangular block of lead (Pb) measures 20.0 mm X 30.0 mm X 45.0 mm. If the density of Pb is 11.34 g/cm3, calculate the mass of the block.

8. A cube of gold (Au) has a side length of 1.55 cm. If the sample is found to have a mass of 71.9 g, find the density of Au.

9. An irregularly-shaped sample of aluminum (Al) is put on a balance and found to have a mass of 43.6 g. The student decides to use the water-displacement method to find the volume. The initial volume reading is 25.5 mL and, after the Al sample is added, the water level has risen to 41.7 mL. Find the density of the Al sample in g/cm3. (Remember: 1 mL = 1 cm3.)

10. If you are sure that a sample of material is aluminum but have no measuring instruments AND are not allowed to handle the sample, how would you determine the sample’s density?

11. A gas has a mass of 3175 g and takes up enough space to fill a room that is 2.00 m X 2.00 m X 5.00 m. Use the table below, which lists densities in units of g/mL to help you determine what the gas is. (Hint: Change the units on the size of the room.)

Answers: 1. 1.01 x 104 g Ag 6A. 25.8 mL HCl 9. 2.69 g/cm3

2. 11 g/cm3 6B. 16.4 mL H2SO4 11. helium3. 1.87 x 105 mL 6C. 24.0 mL HNO3

4. 22.0 mL 7. 306 g Pb5. 118.35 g ethanol 8. 19.3 g/cm3