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. Investigating DensityWorkbook

NAME..... CLASS .

INVESTIGATIONS IN SCIENCE

STUDENT WORKSHEETS

INVEStiGATING DENSITY

John M. Rogan Ph.D.Westl1rD Montana College

CONTENTS

Investiga tion

1. Why do objects float or sink?

Flow chart of the problem to be investigated

2. Does mass alone explain why objects float or sink?

3. Does volume alone explain why objects float of sink?

Information sheet - The concept of density

4. Measuring density

5. The density of an irregular solid

6. The density of water

7. Does density explain why objects float or sink?

8. Density and mass-volume graphs

lllustrations by Susan Arthur

Published by:REDC0 Science

11 Robinson Lane,

Oxford, CT 06483

COPYRIGHT 1986 John M. Rogan

Page

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1 WHY DO OBJECTS FLOAT OR SINK?

PROBLEMWhy do different objects float or sink when put into water?

MATERIALS

Plastic bowl Nail

Wooden block Pin

Plexiglass block Stone

Plastic cube Cork

Glass marble

PROCEDURE

1. Drop each of the objects shown in the diagram into the waterin the bowl. Does the object float or sink? See Q 1.

Ql. Complete the following table.

-Object Does it float or sink?

Q2. Why does an object float or sink? Check one of the folJowing.

It is because of the mass of the object.---

It is because of the volume of the object.---

It is because of some other reason.---

Q3. We are trying to develop a theory which will explain why objects either float or. sink in water. Try to explain the reasoning behind your choice in Q2 in words.

. . . . . . . . . . . . . . . . . . . . . . . . . '1: .

Q4. Outline how you would test your theory to find out whether it is a good one.

2. We will be testing a number of theories about why objects either float or sink inthe worksheets that follow. The sequence is summarized in the chart given on thenext page. Study the chart now. and refer back to it during the next lessons.

VOCABULARY

Theory A theory is a set of ideas put forward to explain certain observations. butwhich have not yet been proved by experimentation.

EXTENSION

Test whether the same objects shown in the diagram on the previous page will sink orfloat in another liquid such as mineral oil or rubbing alcohol.

FLOW CHART OF THE PROBLEM TO BE INVESTIGATED

We are going to do three investigations to find out why.objects float or sink whenplaced in water. Here is a flow chart of the problem.

Why do objects float or sink when put in water?

1. Does mass alone explain whyobjects float or sink whenplaced in water?

We found that ...

(a) Mass alone explainsfloating and sinking.

(b) Mass alone does notexplain floating andsinking.

Circle the correct answer.

What is density?

t

2. Does volume alone explain whyobjects float or sink whenplaced in water?

We found that ...

(a) Volume alone explainsfloating and sinking.

(b) Volume alone does notexplain floating and

sinking.

Circle the correct answer.

What is the density of different materials?

What is the density of water?

t3. Does density explain why objects

float or sink when placed in water?

We found that ...

(a) Density explains floatingand sinking.

(b) Density does not explainfloating and sinking.

Circle the correct answer.