Liquid Density Lab - Sink or Swim
Lesson 6 of 6
Objective: Students will be able to test the density of different objects in water, vegetable oil, and corn syrup.
This lesson is based on California's Middle School Integrated Model of NGSS.
MS-PS1: Matter and Its Interactions
PE: MS-PS1-2 - Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. This lesson is specifically designed to assess the property of density of a substance.
DCI: PS1.A: Structure and Properties of Matter - Each pure substance has characteristic physical and chemical properties.
SP3: Planning and Carrying out Investigations - Students will investigate if their predictions are accurate. They will first predict which objects will float, sink, or flink, in three different fluids. After they have made their predictions they will gather experimental data of what actually occurs and compare their results.
CCC: Patterns - densities are properties of matter. Pure substances have predictable densities that can be determined by their mass and volume. If any two of these values are know the third can be calculated. This predictable pattern can be used in science to determine the make-up of substance through observation alone, i.e. if you can estimate the mass and volume of an asteroid you can make a reasonable guess to its density, which can be compared to know densities to determine what material is in the asteroid.
This lab is often run as part of two other labs:
For this activity, students test and observe how objects of different densities behave in different liquids.
Tested objects (any small objects can be tested - use your imagination)
- Small cork
- Small paperclip
- Fishing weight
Test liquids (over the years I have collected enough glass baby food jars to store these liquids in, so I now have a class set)
- Vegetable oil
- Corn syrup
- Baby food jar - corn syrup
- Baby food jar – vegetable oil
- Baby food jar – water
- Raisins or grape
- Paper clip
- Small cork
- Fishing weight
- Record your predictions about what will happen when you place a raisin, paper clip, small cork, penny, and a marble in three different liquids.
- Gently place a raisin, paper clip, small cork, penny, marble, and a fishing weight in water and record if the items sinks, flinks, or floats.
- Gently place a raisin, paper clip, small cork, penny, marble, and a fishing weight in vegetable oil and record if the items sinks, flinks, or floats.
- Gently place a raisin, paper clip, small cork, penny, marble, and a fishing weight in corn syrup and record if the items sinks, flinks, or floats.
Before the students perform any testing they must first make a prediction of how the different objects will behave in the three liquids. They may predict that the objects will float, sink, or flink. Flink in a made up word we use in my classroom to describe an object that is neutrally buoyant, it is a combination of the words float and sink (float + sink = link). See Flink Lab activity.
After students have made their predictions, they are ready to make the actual tests. To assist the students in retrieving the objects I have several spoons (purchased from a thrift store) that the students can use.
Lab (Student Activity)
Pass out Liquid Density Lab - Sink or Swim to each student. This document contains needed materials, directions, prediction chart, data chart, and review questions.
Before my students can actually test which objects will float and sink they must make predictions FIRST. I often have groups that ignore this step and start right with the actual test.
I tell my students to first lay down a length of paper towels to make cleanup easier (corn syrup is sticky).
The students carefully drop each item into tap water,
and finally corn syrup.
They identify each object as floating, sinking, or flinking (made up word to describe neutral buoyancy).
- Which predictions were right? Explain.
- Did some items float in certain liquids but not others? Why?
- Explain density in your own words.
- Explain buoyancy in your own words.
Student Work Sample