Title: Measuring Volume

Activity 8

Read A-32

Problem:

How do you measure volume of a solid object?

Hypothesis/Initial Thoughts:

Unit A Vocabulary

Metric System

• The measuring system used by scientists and most countries other than the U.S. and United Kingdom

Unit A Vocabulary

VolumeThe amount of space a material takes upmL or cm3

1 mL = 1 cm3

Unit A Vocabulary

Water DisplacementThe amount or water that is moved

(displaced).This determines the volume of the object

that caused the water to be moved.

How would you arrange these objects from the least to the

greatest volume?

• Discuss with your group.

Units of Measurecopy this into your notebook

Common Metric Unit Basic Unit in SI

Length centimeter (cm)meter (m) = 100 cmkilometer (km) = 1000 m

meter

Mass gram (g)kilogram (kg) = 1000 g

kilogram

Volume milliliter (mL) (1 mL = 1 cm3)liter (L) = 1000 mLcubic centimeter (cm3)cubic meter (m3)

cubic meter

• Base Unit

Reading a Graduated Cylinder1. Make sure it is on a flat

surface

2. Bring your eye down to the same level of the fluid’s surface.

3. Read the lowest point of the meniscus (the liquid’s curve)

4. Estimate the volume in mL if it falls between marks.

Reading a Metric Ruler

1. Find cm and mm lines.

2. Make sure you are starting the measurement on the Zero line.

3. Estimate the length if it falls between marks.

4. Make sure your units are correct (cm or mL).

Significant Figures• Depends on the level of accuracy of the

measuring tool

• Consists of all digits know with certainty, plus one final digit

Measuring Length Worksheet

1. D2. D3. C4. B5. Using the ruler

provided:a) 15 cmb) 0.1 cmc) 0.1 cm

6. The length of the pencil is:a) 10.5 cm

b) 14.1 cm

c) 10.0 cm

d) 10.9 cm

e) 9.2 cm

Measuring Volume Worksheet

1. C2. C3. A4. A5. For the 50-mL

graduated cylinder:a) 50 mLb) 4 mLc) 0.5 mL

6. The amount of liquid in the containers is:a) 15 mL

b) 18 mL

c) 21 mL

d) 31 mL

e) 48 mL

Two Methods to Determine Volume

• There are two methods to determine the volume of a solid object.

• You will learn both methods.

• Then will use your judgment to decide which method is the most appropriate to use for measuring particular objects.

Procedure:1. Remove and observe the six objects from

the cup

2. Predict the order of the objects from least to greatest volume. Record prediction.

3. Watch teacher demonstration of how to measure the volume of an object using two methods:

• Measurement and calculation• Water displacement

Prediction:• Which object has the greatest volume?

• Put a number under each object, ordering them from LEAST (1) to GREATEST (3)

Your calculated value cannot be more precise than the least precise measurement

v = l w h or s3

v = πr2h

r = ½ dv = l wh

Method 1:Measurement and Calculation

•Only works for objects that have regular shapes

•Measure and calculate using the appropriate formula

Example: Measure the dimensions of the lt. gray cube

l = 2.5 cm w = 2.5 cm h = 2.5 cm

v = l wh

v = 2.5 cm x 2.5 cm x 2.5 cm

v = 15.625 cm3

v = 15.6 cm3

Appropriate formula

Most precise measurement is tenthstenths

Object Method Used

Meas. Formula & Calc. Volume

Light gray bar Meas.

Displ.

Dark gray bar

Light gray cube

Meas. L = 2.5 cm

w = 2.5 cm

h = 2.5 cm

v = 2.5 cm x 2.5 cm x 2.5 cm v = 15.6 cm3

Dark gray cube

Meas. L = 2.5 cm

w = 2.5 cm

h = 2.5 cm

v = 2.5 cm x 2.5 cm x 2.5 cm v = 15.6 cm3

Light gray cylinder

Meas.

Displ.

Dark gray cylinder

Your choice

Your choice

Method 2: Water-Displacement• How much do you think the water will rise when the light

gray bar is put in it?

• Use a pipette to add or remove water so you can start with a convenient initial volume.

• Irregular objects cannot be measured, so you must use water-displacement.

• Volume = Final Volume - Initial Volume

v = vf – vi (units are mL)

vi = 30 mL ,

v = 37.5 mL – 30 mL

v = 7.5 mL

vf = 37.5 mL

Object Method Used

Meas. Formula & Calc. Volume

Light gray bar

Meas.

Displ. vi = 30 mL

vf = 37.5 mL

v = 37.5 mL – 30 mL v = 7.5 mL

4. Divide objects into two sets, one dark grey & one light gray. Each pair begins with one set.

5. Determine which method is best for determining the volume. Use both methods for lt. gray cylinder & lt. gray bar.

6. Determine volume of each and record data in your table.

7. Exchange object sets and repeat steps 5 & 6.8. Compare your results with the other pair in

your group. Repeat anything you think is inaccurate.

9. Base on you data, list the objects from least to greatest volume. Record in notebook.

Discussion• Were there any differences in your results

for the volumes of the different objects?• What do you think caused them?

– Error in measurements (reading the ruler or graduated cylinder incorrectly)

– Calculation errors

• Final Rankings• Which was more accurate?

– Measurement and calculation because you did not have to round as closely.

– Water Displacement is best for irregular objects