Title: Density

Discipline: Physical Science

Ability: 8th Grade

Time: One 50 Min Class Period

NJ Core Curriculum Content Standards:

Mathematics: 4.1, 4.3, 4.4, 4.5

Science: 5.1, 5.2, 5.5, 5.8, 5.9

Objective: The purpose of this activity is to determine the effects of density on an object by using the scientific method and to determine how to calculate the density of an object.

Pre-activity discussion:

What is density and how do we know about it?

Is the density of different substances different, and how do we know that?

Materials: hard-boiled egg (boiled at least 10 min. and cooled for 20 min.)

graduated beaker of at least 300mL

plastic teaspoon and knife

balance

filter paper to place on the balance

kosher salt

water

metric ruler

Procedure:

1. Place the filter paper on the balance and find its mass. Record it.

(There are pages in the back of the activity where you might

want to record your data.)

2. Carefully so as not to crack the egg shell, place the egg on the

filter paper and find its mass. Be sure to consider the mass of the

filter paper. Record the mass of the egg.

3. Estimate the volume of the egg using the ruler and “Crownian

Thought” i.e., Geoboard technique.

4. On another sheet of filter paper, mass out one level teaspoon of

Salt (use the plastic knife to level the salt). Record the salt’s mass.

5. Fill the graduated beaker with water. Make it at least three-

fourths full. Record the water level.

6. Gently add the egg to the water (there should be about 10 cm/or

10mL of water over the top of the egg – if there isn’t, remove the

egg carefully and add more water and redo steps 5 and 6.

7. Record the water level with the egg in the beaker and note the displacement of water.

8. Gradually add salt to your beaker, add it one level teaspoonful at a time, stir gently to dissolve the salt, then wait, observe, and discuss with your group what you think will happen and why; what is happening and the possible reasons. Record your observation by drawing your set-up. Show where the egg is located and write any information you think will be helpful.

9. Continue to add the salt, stir, wait, observe, and record until a big change occurs in the beaker. Explain the change.

Group Reflections (Conclusions):

Discuss the concept of density as it seems to relate to the hardboiled egg and the water it is in. What role did the salt appear to play in this relationship?

Are there any real-life applications for our new understanding of the effects of salt on the density of water? Have you seen this same relationship anywhere during outdoor summer activities? Can you think of a way this new understanding would be helpful in teaching someone a particular activity?

How can you find the density of the egg?