Objectives
Students will
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define intrinsic and extrinsic properties;
determine if density is an intrinsic property or extrinsic property;
determine the density of various liquids;
record data in a table;
use the following skills: observing and recording data (observations), inferring
from observations.
Motivation for Learning
Discrepant Event
Do two simple demonstrations to illustrate the key concepts studied in the lab exercise.
To differentiate extrinsic properties from intrinsic properties:
Materials
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Two 250 mL beakers
300 mL water
Thermometer
Hot plate
100 mL graduated cylinder
Procedure
1. Mass both beakers separately and record the results on the chalkboard.
2. Place 100 mL of water in one of the 250 mL beakers. Mass and record the results
on the chalkboard.
3. Place 200 mL of water in the other 250 mL beaker. Mass and record the results on
the chalkboard.
4. Determine the mass of the water in each beaker by subtracting the mass of the
beaker from the mass of the beaker and the water. Record the results on the
chalkboard.
5. Place both beakers on the hot plate and bring them to the boiling point.
6. At this point define the terms extrinsic property and intrinsic property and ask the
students which one mass is. (Mass is an extrinsic property.) Also ask them if mass
would be useful in determining that both beakers actually contained water.
Discuss some other examples of extrinsic properties and point out that extrinsic
properties are not useful in determining the identity of a substance.
7. When the beaker containing 100 mL of water begins to boil, measure the
temperature and record it on the chalkboard.
8. When the beaker containing 200 mL of water begins to boil, measure the
temperature with the same thermometer and record it on the chalkboard.
9. Compare the boiling point temperatures. (They should be the same.)
10. At this point ask the students if boiling point is an extrinsic or intrinsic property.
(Boiling point is an intrinsic property.) Also ask them if boiling point would be
useful in determining that both beakers actually contained water. Boiling points
are generally unique for any given substance. Discuss some other examples of
intrinsic properties and point out that intrinsic properties are very useful in
determining the identity of a substance.
To demonstrate that different liquids can have different densities:
Materials
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75 mL cooking oil
225 mL water
Food coloring (any color)
Four 150 mL or 250 mL beakers
100 mL graduated cylinder
Procedure (Part 1)
1. Pour 75 mL of water into a beaker and then add one or two drops of food coloring
to the water and mix.
2. Pour an equal amount (75 mL) of water into another beaker.
3. Explain to the students that you are going to pour the colored water into the clear
water and have them hypothesize what will happen.
4. Gently pour the colored water into the beaker of clear water and observe.
5. Discuss the results. The contents of the beaker will mix and the food coloring will
diffuse throughout the mixture. Eventually, the color will be uniform. You can stir
the mixture to speed up the process of diffusion.
Procedure (Part 2)
1. Pour 75 mL of water into a beaker and then add one or two drops of food coloring
to the water and mix.
2. Pour an equal amount (75 mL) of cooking oil into another beaker.
3. Explain to the students that you are going to pour the colored water into the
cooking oil and have them hypothesize what will happen.
4. Gently pour the colored water into the beaker of cooking oil and observe.
5. Discuss the results. Why does the colored water sink to the bottom? Students will
probably answer that the colored water weighs more. Remind the students that
you used equal amounts of water and proceed with the experiment below. If you
stirred the mixture in part 1, then you should stir the mixture in part 2. It will only
take a minute for the mixture to separate again. In the assessment question
section, students will return to the question - Why did the colored water sink to
the bottom of the beaker of cooking oil? The answer is that the colored water has
a greater density than the cooking oil. At this point in the activity, students should
be able to draw this conclusion utilizing their experimental results. You can
illustrate this concept in a post lab discussion by placing a piece of copper or
similar metal into a beaker or glass of water. The copper will sink to the bottom
because it has a density of 8.96 g/cm3, while water has a density of 1 g/cm3.
Background Information
Density is the ratio of mass of an object to its volume (D = mass/volume) and is generally
reported in grams per cubic centimeter (g/cm3). You may recall that a milliliter (mL) is
the same as a cubic centimeter (cm3). In this lab exercise, students will determine the
density of various amounts of different liquids in order to determine if density is an
extrinsic property (dependent on the amount of matter) or an intrinsic property
(dependent on the type of matter). Examples of extrinsic properties include volume, mass,
weight, and temperature. Examples of intrinsic properties include density, color, texture,
freezing point, and boiling point. This activity allows students to perform several density
calculations or to use a computer spreadsheet to generate the data. Then students
interpret the data to answer the question - Is density an extrinsic or intrinsic property?
This activity will probably require two 50-minute class periods.
Student Activity
Materials
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100 mL of 3 liquids (recommend cooking oil, water, and rubbing alcohol to
maintain continuity with the discrepant events)
3 150 mL or 250 mL beakers, one for each liquid
Triple beam or electronic balance
100 mL graduated cylinder
Procedure
1. Determine the mass of a clean dry graduated cylinder - record in data table.
2. Measure out 50 mL of water- record amount (50 mL) in data table. (Remember always measure from the bottom of the meniscus.)
3. Determine the mass of the graduated cylinder and the liquid together and record it
in the data table.
4. Pour the liquid back into its container for reuse.
5. Subtract the mass of the cylinder from the mass found in step 3. This gives the
mass of the liquid alone. Record it in the data table.
6. Calculate the density of the liquid by dividing the mass by the volume. Record it
in the data table.
7. Repeat steps 1-6 using 75 mL of water.
8. Repeat steps 1-6 using 100 mL of water.
9. Repeat steps 1-8 for the other 2 liquids provided.
Data Sheet
Water
Mass of Graduated Volume
Cylinder (g)
(mL)
Mass
Mass
Density of
GC+Liquid (g) Liquid (g) Liquid (g/mL)
Trial
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Trial
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Trial
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Oil
Mass of Graduated Volume
Cylinder (g)
(mL)
Mass
Mass
Density of
GC+Liquid (g) Liquid (g) Liquid (g/mL)
Trial
1
Trial
2
Trial
3
Alcohol
Mass of Graduated Volume
Cylinder (g)
(mL)
Trial
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Trial
2
Trial
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Mass
Mass
Density of
GC+Liquid (g) Liquid (g) Liquid (g/mL)
Assessment
(Please answer in complete sentences!):
1. As the volume of the liquid increases, what happens to its mass?
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2. As the volume of the liquid increases, what happens to its density?
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3. Based on your experimental results, is density an extrinsic or intrinsic property?
Explain.
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4. From the colored water and cooking oil classroom demonstration, explain why
the colored water sank to the bottom of the beaker. Use data from your
experimental results to support your answer.
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Answers to Assessment
1. If the volume of a liquid is increasing then more of the liquid must be
being added; therefore, the mass of the liquid is increasing.
2. The density of a liquid is constant despite mass and volume.
3. Density is an intrinsic property because it is based on the chemical nature
of the pure liquid or the combined chemical natures of the liquids within a
solution and not the physical properties of the specific matter (i.e.
temperature, mass, and/or volume). These results show that the density
does not change when the extrinsic properties change and therefore is not
related to these.
4. The cooking oil is less dense than the water; thus, due to gravity, the water
(with a higher density) will sink to the bottom. Because the cooking oil is
made up of hydrophobic carbon compounds (which don't like the polar
behavior of water), the two substances stay unmixed.