Teacher Portal:

Exploring Density

Investigation 1 – Lab

Back to Investigation 1

BE PREPARED

Supplies and Equipment:

Class Materials:

15 100 ml beakers
1 roll of masking tape 1 marker
500 ml water
625 ml vegetable oil 325 ml rubbing alcohol Red food
coloring
3 liter pitchers
1 glass stir rod
2 ice cube trays

Group Materials:

3 100 ml graduated cylinders 3 100 ml beakers
1 metal cube
3 paper towels
3 ice cubes

Individual Materials:

1 Student Data Record

Teacher Preparation:

1. Using the ice cube trays, make ice the day before the investigation or obtain ice cubes the day of the investigation.

2. Fill five 100 ml beakers with 25 ml of water. Label beakers “A.”

3. Fill five 100 ml beakers with 25 ml of water. Label beakers “B.”

4. Fill five 100 ml beakers with 25 ml of vegetable oil. Label beakers “C.”

5. Fill one liter pitcher with 500 ml of vegetable oil. Label pitcher “vegetable oil.”

6. Fill one liter pitcher with 325 ml of rubbing alcohol. Add 5 drops of red food coloring and stir until completely mixed. Label pitcher “rubbing alcohol.”

7. Fill one liter pitcher with 250 ml of water. Label pitcher “water.”

8. Organize the required materials at a distribution point.

9. Divide students into 5 cooperative groups.

Instruction:

1. Direct each student group to obtain the following necessary materials from the distribution point: three (3) 100 ml graduated cylinders, three (3) 100 ml beakers, one (1) metal cube, three (3) paper towels, three (3) ice cubes, and three (3) beakers labeled A, B, and C.

For Trial 1, instruct students to use the liter pitchers at the distribution center to fill two (2) graduated cylinders each with 25 ml of water and one (1) graduated cylinder with 25 ml of vegetable oil.

For Trial 2, instruct students to use the liter pitchers at the distribution center to fill one (1) 100 ml beaker with 50 ml of rubbing alcohol, one (1) 100 ml beaker with 50 ml of water, and one (1) 100 ml beaker with 50 ml of vegetable oil.

GET FOCUSED

Investigation One introduces students to the relationship between mass, volume, and density.

INVESTIGATE

Ask students: Which liquid do you Predict is going to be more dense? Least dense? Explain your predictions. Student predictions will vary. Encourage students to record their predictions in Problems 2a, 2b, and 2c of their Scientist Data Record.

Trial 1

2. In Trial 1, students will compare how water, rubbing alcohol, and vegetable oil interacts with each other by combining water and rubbing alcohol, water, and vegetable oil, and rubbing alcohol and vegetable oil. Students will then observe which liquid “sinks” and which liquid “floats” in each combination. Students will discover that water has the greatest density of the three liquids and that rubbing alcohol has the lowest density of the three.

As students complete this Trial, ask them to consider the following question: How do the densities of two liquids affect what happens when they are added together?

Trial 2

3. In Trial 2, students will compare how the density of solids and liquids may determine whether a given solid “sinks” or “floats” in a particular liquid. Students will investigate how the density of a metal cube and an ice cube affect their interaction with water, rubbing alcohol, and vegetable oil. Students will discover that the density of the metal cube is greater than the density of all three liquids, and may form the opinion that solids have a greater density than liquids. However, students will discover through experimentation with the ice cube that solids do not always have a greater density than liquids, as the ice cube only “sinks” in the alcohol. Students should consider the following questions: