Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 3 WS 1

INTRODUCTION

There are a number of important properties that assist in identifying elements and pure compounds. These include density, melting point and boiling point.

The density of a substance is the measure of its compactness and is calculated from the ratio:

density mass (g)

volume (mL)

In this experiment you will:

a measure the mass of several different volumes of water and use these to calculate the density of waterb use a similar procedure to calculate the density of ice.

EXPERIMENT: INVESTIGATING THE DENSITY OF WATER AND ICE

Syllabus reference 8.4.1

WORKSHEET1

EQUIPMENT❍ 100 mL beaker❍ wide diameter measuring cylinder❍ electronic balance❍ distilled water❍ ice cubes (made with distilled water and small enough to fit into the measuring cylinder)❍ 10 mL pipette❍ forceps or glass rod❍ thermometer

Part A: Density of water

PROCEDURE1 Accurately measure the mass of the empty beaker. Record this in the table below.

2 Add a known volume of distilled water (use the pipette) to the beaker and reweigh. Record this in the table.

3 Measure the temperature of the water.

4 Repeat this procedure until you have at least 5 measurements (use 10 mL increments from the starting volume). Record all measurements in the table.

MODULE 3

Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 3 WS 1

RESULTS1 Complete the table.

2 On the grid paper below plot the experimental values for volume in mL (horizontal axis) and mass in g (vertical axis).

3 Use a ruler to draw the ‘line of best fit’ which goes through the origin.

4 The slope of the line is a measure of density. From the graph calculate the slope and hence the density of water.

density _______________

5 Record the results of the other groups in the class.

DENSITY OF WATER AT __________________ºC

TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5

Mass of 100 mL measuring cylinder (g)

Mass of measuring cylinder + water (g)

Mass of water (g)

Volume of water (mL)

Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 3 WS 1

QUESTIONS1 How did your value compare with those of the rest of the class?

2 Suggest possible reasons for variations between groups.

Part B: Density of ice

Design an investigation to calculate the density of ice.

HINT: The volume of solids is often measured using a known mass and submerging it in water (use forceps or a glass rod to keep your ice cube submerged). The rise in the water level is equal to the volume of the solid.

PROCEDURE

1

2

3

RESULTS

TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5

Mass of sample (g)

Volume of sample (mL)

Density (g/mL)

DENSITY OF ICE (g/cm3)

Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 3 WS 1

QUESTIONS1 Calculate the average density from your trials.

2 Did you expect the density of ice to be less than or greater than that of water? How did your experimental results compare with your expectation?

3 How did your value compare with those of other groups in the class?

4 Discuss any difficulties you encountered with this investigation. What errors may have occurred? How could you improve on this investigation?