Summary

In this teacher led demonstration, students will compare their observations when unopened cans of diet and regular soda are placed in a large container of water. They will use their observations to help differentiate between several fundamental chemistry concepts: mass, volume, and density.

Grade Level

Elementary School

NGSS Alignment

This demonstration will help prepare your students to meet the performance expectations in the following standards:

• 5-PS1-3: Make observation and measurements to identify materials based on their properties.
• Scientific and Engineering Practices:
  • Analyzing and Interpreting Data

Objectives

By the end of this demonstration, students should be able to

• Differentiate between the concepts of mass, volume, and density.
• Explain why some items float and other items sink.
• Predict whether or not an item will sink or float given density information.

Chemistry Topics

This demonstration supports students’ understanding of

• Density
• Mass
• Volume
• Measurement

Time

Teacher Preparation:15 minutes

Lesson: 45 minutes

Materials

• 1 large sheet of chart/poster paper
• Post it notes, 3 post it notes for each pair of students (optional)
• Large transparent container of water (ex: aquarium, clear plastic tub, etc.)
• 1 can of regular coke, unopened
• 1 can of diet coke, unopened
• Scale

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• This demonstration was designed for use in grades 3-5, however it can be modified to be used in additional grade levels.
• The teacher should begin by briefly reviewing background information with use of a chart on large poster paper/white board. Divide the paper into 3 columns labeled mass, volume, and density.
• After reviewing background information with students, have them work with a partner to come up with one fact for each column on post-it notes. Have students share some of their facts and place the post it notes on the chart paper. (If chart paper and post its are not available, each student can get a copy of the 3 column chart included on the student lesson)
• Background Information:
  • Mass: the amount of matter that makes up an object. To find the mass of an item, you can use a balance. Objects with the same volume do not always have the same mass.(Often measured in grams- one paperclip is about 1g).
  • It is important to note that mass and weight are not the same thing. Weight is the measure of the amount of pull or gravity on an object.
  • Volume: the amount of space a substance takes up. Volume can be measure in solids, liquids or gases. To find the volume of a liquid, you can use a beaker or measuring cup.Finding the volume of a solid is more difficult. You need to place a solid in water and find the volume with and without the item in it. The difference is the solid’s volume. This is called water displacement method.
  • Density: the amount of matter in a given space. To find Density, you divide the Mass by the Volume. Density determines if something will float or sink. Objects will float if they are less dense than the liquid it is in. Objects will sink if they are denser than the liquid they are place in.
  • The density of water is 1g/cm³ or 1g/ml. If an object has a density less than this, it will float in water. If the density is greater than that, it will sink in water.
• Engage students: Ask students if they float in water? Ask for students to offer examples some items that can’t float and allow time for students to share some ideas.
• In the front of the class, teacher will have a large clear container (aquarium, large plastic tub, etc.) filled with room temperature water. The teacher will also have an unopened can of regular coke and a can of diet coke next to the container.
• Show students the cans. Ask them to examine the cans and describe how they are the same and if there are any differences. Ask students to turn to a partner and predict whether or not the cans will float or sink. Ask students to explain the reasoning for their prediction.(Possible answers can include: The cans are made of the same material, both cans are the same volume (12 oz.), the cans are the same shape).

• Teacher will place the unopened can of regular coke in the water and then ask students if their prediction was correct. (The regular can of coke will sink).
• Leaving the regular coke can in the container, the teacher will then also place the unopened can of diet coke in the water and ask students to try to explain their observations. (The diet coke can will float).
• Teacher should explain that diet coke is less dense than the water so it floats. Remove the can from the water and allows students to examine both cans. Lead students to wondering about the possible difference in mass of the diet and regular coke. Using the balance, measure the mass of each can.
• Although both drinks have the same volume and are both composed mostly of water, due to the differences in the amount of high fructose corn syrup (in the regular coke) versus the amount of aspartame (in the diet coke), the mass of the cans are slightly different. In turn the density values of each are different, diet coke has a density ~1g/ml, while regular coke has a density of ~1.03g/ml. For more information, you may find this article helpful.