Fill a large glass with water even to the
rim. Ask students, “Is this glass of water full? How many paper
clips do you think I could add to this glass of water, before the
water overflows?” Students will see that you can add many more
paper clips to the glass than they thought.
Follow this demonstration with another quick
Give a penny, pipette, and a small jar
of water to every fourth student.
Have groups of four (at their desks)
first estimate how many drops of water the surface of the penny will
hold before the water spills over the sides, and then perform the
Have students place the penny on the
desk and begin to place as many drops of water as they can on the
coin until water runs off the surface of the penny.
For an extension, students could try this
same demonstration with isopropyl alcohol or an alkane, such as
hexane, instead of water.
Ask students, “Why do you think you can
add several more paper clips to the already full glass of water? Why
could you add more drops of water to the penny than you could with
alcohol or hexane?” Let students make educated guesses. Some
may offer answers such as, the water is denser or it sticks together
more. Tell them, “All of the substances that we looked have
unique physical properties. The physical property you just explored
is called surface tension, which allowed the water molecules to cling
to the side of the glass and the penny.”
Let this answer guide you into a discussion
of physical properties. Put the definition of physical properties on
the board, overhead or interactive white board. Working with water,
ask students to brainstorm other physical properties of water. On the
board, make a list of their answers. When you feel that they have
exhausted their guesses, circle the ones that are correct and then
add properties that were not yet guessed. Define each. Below is a
list of some physical properties. You may add to or remove from the
list any properties you want.
Viscosity: Viscosity describes a liquid’s resistance to
flow. Greater resistance is higher viscosity.
Density: Density is a physical property that describes how
much mass is in a specific volume. D = m/v.
Conductivity: Describes how well something conducts
Magnetism: Describes how matter responds to a magnetic field.
Boiling/Melting/Freezing Point: The temperature at which a
Thermal Expansion/Contraction: Describes the change in volume
as a substance is heated or cooled.
Malleability: How easily a substance can be molded, bent, and
Ductility: the extent to which a material can be deformed
plastically without fracturing.
Surface Tension: The cohesive forces between liquid
Volatility: A measure of the tendency of a substance to
Demonstrate some of water’s physical
Demonstration 1(Boiling Point)
Set up a distillation apparatus on the front counter. Add tap
water and food coloring to the round bottom flask. Let the water
distill for a few minutes. Explain that distillation “is a
method of physically separating a mixture based on the boiling
points of the components in the mixture. The mixture is made from
water and food coloring. Water has a specific boiling point (at a
given pressure), which is 100ºC. Food coloring has a higher boiling
point than water. You will see the water boil first, vaporize into a
gas, and then condense back into liquid water (because of the cool
water running around the outermost channel). Eventually, you will be
left with just dye in the round bottom flask and pure water in the
beaker.” If you do not have access to a distillation
apparatus, you can show students a distillation animation, such as
Demonstration 2 (Thermal Contraction/Expansion)
Ask students, “Has anyone left a can of soda in the freezer
or in a cold car too long?” Most students have had experience
with this and will acknowledge that the can exploded. Then ask, “Of
what is soda mainly made?” Students might say sugar, bubbles,
and water. Focus on water, which is over 90% of soda’s volume.
“Soda is mainly water, which, unlike most liquids, expands when
it freezes! This is a physical property of water, called thermal
If you have access to liquid nitrogen, you
could fill a balloon with helium and place it in the liquid nitrogen
to see that helium contracts when it is cooled, unlike water. If you
do not have access to liquid nitrogen, you could demonstrate the same
thing by placing the balloon in the freezer for about an hour.
Demonstration 3 (Density)
Introduce this next physical property with a glass of ice water
sitting on the front table. Ask students what they notice about the
glass. Lead them to thinking about why the ice cubes are floating on
the liquid water. Remind them that the solid ice and liquid water
are the same thing, just in different states. Explain, “Solid
water is less dense than liquid water. As water freezes, it expands,
creating more volume. Since density is a function of volume, solid
water is less dense. Less dense substances will float!” Do a
follow up demonstration using isopropyl alcohol (rubbing alcohol).
Fill a graduated cylinder with the alcohol and place ice cubes in
the cylinder. The ice will sink because it has a greater density
than isopropyl alcohol.
In a clear tank (an empty aquarium would
work) place several liters of water. In front of students, place a
can of cola and a can of diet
cola into the tank. Explain, “There is considerably more
mass per unit volume in the regular cola than the diet cola, causing
it to be denser and sink.”
Demonstration 4 (Conductivity)
Place a sample of distilled water that you purchased from the
store (or use the distilled water from Demonstration 1) in a
beaker. Use a conductivity set with a light bulb to show that
distilled water is a poor conductor of electricity. Do the same with
salt water, which will be a better conductor.
Demonstration 5 (Viscosity)
Pour a small amount of honey from a high height (so students can
see) into a jar. Do the same with water. Ask, “which substance
has a higher viscosity, remembering that viscosity is resistance to
- Use the Physical Properties Lab–Teacher Version sheet (S-8-5-1_Physical Properties Lab Teacher Version.doc) to set up the Physical Properties lab and to correct and
assess students’ work when they have finished the lab. Assign
students to teams. Hand out Physical Properties Lab–Student
Version (S-8-5-1_Physical Properties Lab Student Version.doc) to students. In their groups, they should complete
the information tables on the unknown substances and answer the
For students performing above and beyond the standards,
consider discussing fractional distillation, used in the petroleum
industry. For details and an animation of this process, go to:
If you have access to dry ice (CO2), you can place
about 3 cups of it in an aquarium. Let it sublimate for 10 to 15
minutes. Light a candle. Take a beaker and “scoop” out some of
the CO2 vapor. It will look to students as if you are not
removing anything. Quickly pour the vapor over the burning candle.
The flame will extinguish due to the density of CO2.
Relate this to fire extinguishers.