Transcript Activity 8 Title: Measuring Volume Read A-32 Problem: How do you measure volume of a solid object? Hypothesis/Initial Thoughts:

Activity 8
Title: Measuring Volume
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
Volume
The amount of space a material takes up
mL or cm3
1 mL = 1 cm3
Unit A Vocabulary
Water Displacement
The 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 Measure
copy this into your notebook
Common Metric Unit
Basic Unit in SI
Length
centimeter (cm)
meter (m) = 100 cm
kilometer (km) = 1000 m
meter
Mass
gram (g)
kilogram (kg) = 1000 g
kilogram
Volume
milliliter (mL) (1 mL = 1 cm3)
liter (L) = 1000 mL
cubic centimeter (cm3)
cubic meter (m3)
cubic meter
• Base Unit
Reading a Graduated Cylinder
1. 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.
2.
3.
4.
5.
D
D
C
B
Using the ruler
provided:
a) 15 cm
b) 0.1 cm
c) 0.1 cm
6. The length of the
pencil is:
a)
b)
c)
d)
e)
10.5 cm
14.1 cm
10.0 cm
10.9 cm
9.2 cm
Measuring Volume Worksheet
1.
2.
3.
4.
5.
C
C
A
A
For the 50-mL
graduated cylinder:
a) 50 mL
b) 4 mL
c) 0.5 mL
6. The amount of
liquid in the
containers is:
a)
b)
c)
d)
e)
15 mL
18 mL
21 mL
31 mL
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)
v=lwh
or s3
v = l wh
v = πr2h
r=½d
Your calculated value cannot be more
precise than the least precise measurement
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
v = l wh
h = 2.5 cm
Appropriate formula
v = 2.5 cm x 2.5 cm x 2.5 cm
v = 15.625 cm3
v = 15.6 cm3
tenths
Most precise
measurement is
tenths
Object
Method
Used
Meas.
Formula & Calc.
Volume
Light gray bar
Meas.
Displ.
Dark gray bar
Your
choice
Light gray
cube
Meas.
L = 2.5 cm v = 2.5 cm x 2.5 cm x 2.5 cm
w = 2.5 cm
h = 2.5 cm
v = 15.6 cm3
Dark gray
cube
Meas.
L = 2.5 cm v = 2.5 cm x 2.5 cm x 2.5 cm
w = 2.5 cm
h = 2.5 cm
v = 15.6 cm3
Light gray
cylinder
Meas.
Displ.
Dark gray
cylinder
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 ,
vf = 37.5 mL
v = 37.5 mL – 30 mL
v = 7.5 mL
Object
Method
Used
Meas.
Formula & Calc.
Volume
vi = 30 mL
vf = 37.5 mL
v = 37.5 mL – 30 mL
v = 7.5 mL
Light
Meas.
gray bar
Displ.
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