Sink or Float Science Experiment

Instructor: Shelby Golden
This physics experiment can be used to learn more about the factors involved with buoyancy. Working on this lab involves determining what causes objects to float or sink.


Research Question: Why do some objects sink while other objects float?
Age: Elementary and up
Time to complete: Approximately 30 mins
Safety Concerns: None
Independent variables:
mass and volume

Dependent variable: density (density = mass/volume)
Controlled variables:
the amount of water used
water's density (1g/mL)

What determines whether an object sinks or floats? Size or weight are easy guesses, but we know that large, heavy boats can successfully float across bodies of water, while smaller, lighter objects like pebbles sink right away.

However, objects have other qualities as well, such as density. Could this feature be responsible for an item's buoyancy? Let's find out by conducting this experiment! If you aren't familiar with the principles of buoyancy yet, you can read this lesson, What is Buoyancy?, to find out more.

I order to determine why some items sink and others float we're going to measure the mass of some common foods and then submerge them in water to observe how they react. We can then use the formula for finding density to determine if an object's density correlates to whether it sinks or floats.

Do Apples Float or Sink?
apples floating in water


You will need to following supplies to conduct this experiment:

  • 4-5 types of fruits or vegetables, try to include an orange or banana
  • Scale
  • Clear beakers marked in mL
  • Water
  • Worksheets such as this one:

Object Mass Volume Hypothesis Outcome Density
1 1 1 1 1 1
2 2 2 2 2 2


1. We're going to weigh each object and record our findings on the worksheet before determining whether we think it will sink or float based on weight. Record predictions under the hypothesis line of the worksheet.

2. Add water to the beakers and then place objects in the water. Record whether they sink or float, as well as the amount of water they displace (this is their volume).

3. Determine the density of each object. Use the equation for finding density (density = mass/volume) and compare the density of the items to the density of water. You can get more tips for completing this calculation with this lesson on how to calculate the density of solids or liquids

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account