Introduction: Prior to beginning the lesson: (1) Cut out and laminate Vocabulary Cards for display in the classroom; (2) Photocopy How Dense is Salt Water? (1 per student); (3) Prepare a pitcher of salt water and a pitcher of fresh water.


Group Size: Small Groups


Learning Objectives:

Students will be able to:

·          Explain the term density.

·          Use the scientific process to conduct and experiment (hypothesis, procedure, results, conclusion).


Materials: Vocabulary Cards (see attachment), How Dense is Salt Water? (see attachment), clear plastic cups (1 per group), eggs (2 per group), fresh water, salt water, pitchers.



1.       Ask students: What kind of water is in the ocean? Call on a student to answer. Tell students: Today we are going to learn more about salt water.

2.       Display vocabulary card “density”. Call on a student to read the word, and then tell students: Density is how heavy the water is.

3.       Tell students: Today you are going to be scientists again. You are going to perform an experiment to find out if what is denser: salt water or fresh water.

4.       Divide students into small groups of three or four. Distribute a copy of How Dense is Salt Water? to each student.

5.       Tell students: The first step to your experiment is to come up with a hypothesis. Display vocabulary card “hypothesis”. Tell students: A hypothesis is a guess about what will happen. Your hypothesis might say I think the salt water will be denser than the fresh water. Or it might say I think the fresh water will be denser than the salt water. Give students’ time to record their hypotheses.

6.       Distribute one cup and one egg to each group. Fill the cup about three-quarters with fresh water, and instruct students to gently place the egg in the cup.

7.       Tell students to observe the egg in the cup. Display vocabulary card “observation” and remind students: An observation is something you discover by watching or observing.

8.       Instruct students to draw what they observe on their paper.

9.       Repeat the same procedure for salt water.

10.    Ask students: When did the egg sink? When did the egg float? Tell students: What we observe are the results of the experiment. Write down your results for step #3.

11.    Ask students: Why do you think the egg floats in the salt water and sinks in the fresh water? Give students time to share guesses.

12.    Tell students: The egg floats in the salt water because when salt is added to water the water become heavier than the egg. The egg sinks in the fresh water because the water is lighter than the egg. Therefore salt water is denser than fresh water. Give students time to write down their conclusions.

13.    Clean up all supplies and tell students: We will continue to learn more about oceans tomorrow.


Modifications: For students with special needs, provided one-on-one assistance as necessary.


Assessment: Direct students to turn to a classmate and share one thing they learned today.


Benchmark or Standards:

National Science Education Standards

NS.K-4.1 Science as Inquiry – As a result of the activities in Grades K-4, all students should develop:

·          Abilities necessary to do scientific inquiry.

·          Understanding about scientific inquiry.

NS.K-4.4 Earth Science– As a result of the activities in Grades K-4, all students should develop an understanding of:

·          Properties of Earth materials.

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