Salt Water Density

3.7 based on 36 ratings

Updated on May 15, 2013


Physical Science


K – 2nd grades

Difficulty of Project

Less than $5.00

Safety Issues

To prevent drowning, young children should not be left unattended around water

Material Availability

Readily available or easily purchased at a grocery store

Approximate Time Required to Complete the Project

Less than 30 minutes to collect the data; one day to prepare the science fair display.

To investigate the density of salt water

  • Large, clear jar
  • Egg
  • Water
  • Salt
  • Measuring spoons

Prior to starting this investigation, review the concepts of sink and float. Two factors affect an object’s ability to sink or float: density and buoyancy. An object sinks because it is denser or heavier than the water. Adding salt to the water causes the water to become denser.

In this investigation, the egg floats in the salt water because the salt water is denser than the egg.


density: how heavy something is for its size

buoyancy: the force that causes something to float


Salt water is denser than fresh water. Because of its density, things float more easily in salt water.

Research Questions
  • Why do some things float and some things sink?
  • Is it possible to make an egg float?

  1. Gather the necessary materials.
  2. Fill the jar with about ¾ full with water.
  3. Carefully place the egg in the water. Observe and record results.
  4. Remove the egg from the water.Add one tablespoon of salt to the jar of water.
  5. Carefully place the egg in the water.Observe and record the results.
  6. Continue to repeat steps 4 and 5 each time adding an additional tablespoon of salt until there is a noticeable change.Observe and record the results after each addition of salt.


“Density and Buoyancy: Making Eggs Float” at

“Principle of Buoyancy” at

“Buoyancy Basics” at

“Float, Sink or Swim” by Anne Hance at, 1994

Nancy Rogers Bosse has been involved in education for over forty years â first as a student, then as a teacher, and currently as a curriculum developer. For the last fifteen years she has combined a career in freelance curriculum development with parenthood â another important facet of education and probably the most challenging. Nancy lives in Henderson, Nevada with husband and their three teenagers.