Changes in States of Matter Involving
Carbon Dioxide
8th Grade
Vanderbilt Student Volunteers for Science
Training Presentation
Fall 2013
Important!!!
• Please use this resource to reinforce your
understanding of the lesson! Make sure you
have read and understand the entire lesson prior
to picking up the kit!
• We recommend that you work through the kit
with your team prior to going into the classroom.
• This presentation does not contain the entire
lesson—only selected experiments that may be
difficult to visualize and/or understand.
Before you begin…
• Give each group two instruction sheets (contains
thermometer diagram back to back with instruction
sheet). You will still need to guide them through the
procedures, and making sure they are completing the
observation sheet.
• SAFETY NOTE: Students should not hold
pieces of dry ice. The temperature of dry ice
is -78° C, and students could get frostbite
burns if their skin is in contact with dry ice
for more than a few seconds.
• Students should use tongs to put dry ice into
cups etc.
I. Introduction
• Please refer to manual for detailed
explanations and descriptions.
A. Discuss the states of matter –
solids, liquids and gases.
• There are 5 processes involved in
changes of state (freezing,
melting, vaporization,
condensation and sublimation.
• Have students name the physical
changes that lead to changes of
state.
B. What is CO2?
• Discussion of cold temperature of
dry ice
I. Introduction (Cont.)
Demonstration: Freezing water
with dry ice
• Pour some dry ice into the
insulated container (wear gloves).
• Pour water to about 1 cm depth.
• Place cup in insulated container
with dry ice and wait until the end
of the lesson to show students the
cup of water, which has now been
changed into ice
II. Comparing Dry Ice to Water Ice
• Give a plate, bags, tongs, ice and dry
ice to PAIRS. Remind students that
they should not touch the dry ice.
• Tell students to use their tongs to put a
piece of dry ice into a ziploc bag and
regular (water) ice into the other bag
and close the ziploc fastener.
• Ask the students to describe the
appearance of the two types of ice and
to observe both pieces of ice in the for
a few minutes.
• Have students describe what happens
and record their observations on the
observation chart. What changes in
states occurred?
The dry ice ziploc bag will inflate
because of the CO2 gas being given
off by the solid.
II. Comparing Dry Ice to Water Ice
•
Tell students to open the ziploc
bags and carefully empty the
pieces of dry ice and ice onto the
aluminum pan.
•
Tell students to leave the two
pieces of ice on the aluminum
pan, do not move them, but
observe them periodically to see
what happens over time.
•
Compare the dry ice with the H2O
ice and record observations .
–
–
Water ice leaves a puddle, dry ice
sublimes to a gas.
“Smoke” comes off dry ice (water vapor
in the air condenses around dry ice).
III. Observing Changes of State
Using Dry Ice
•
•
•
•
•
Give each pair a clear plastic cup that is about onethird full of “ocean” water.
Show the students the universal indicator and tell them
that it is used to measure the acidity of liquids. Have
them look at the Universal Indicator chart.
Tell students to:
– add a squirt of universal indicator to the water
and observe the color.
– add regular ice to the cup and ask them whether
it sinks or floats.
– use their tongs and place a piece of dry ice into
the water. Does it sink? Start observing and
record the color changes as soon as the dry ice is
added to the cup.
– Record everything they observe and to record all
the phase changes.
Ask the students to share something they observed.
Draw a picture of the cup (shown below) on the board
and record the different observations from the
students.
Have the students identify the changes in the states.
III. Observing Changes of State
Using Dry Ice (cont’d)
• Observations (see manual for
explanations)
• Dry ice gives off bubbles when it
is added to water.
• A white fog appears over the
water in the top of the glass.
• The white fog stays in the top of
the glass and any white fog that
leaves the glass goes down along
the side of the glass rather than up
into the air.
• Fog that goes down along the
glass disappears near the bottom
of the glass.
• Universal Indicator turns red.
• Dry ice sinks, regular ice floats.
IV. Discussion on the Effect of
CO2 in Oceans
• Write on the board: carbon dioxide sink, acidification
• Ask the students what they know about the effect of carbon dioxide on the
atmosphere? See manual.
• Ask the students what they know about the effect of carbon dioxide on the
oceans? See manual.
• Write the following equation on the board:
CO2
+
Carbon dioxide
H2O
water
→
H2CO3
carbonic acid
• Water in the oceans can remove CO2 directly from the air.
– Oceans are called sinks for CO2.
• Ask students if they can think of consequences of dissolving increasing
amount of carbon dioxide in ocean waters? (Ocean becomes more acidic).
– Acidification could adversely affect marine life. Corals and shells are composed of calcium
carbonates which can dissolve in acidic water.
– CaCO3(s) + CO2(g) + H2O → Ca(HCO3)2 (aq)
V.CO2 as a Fire Extinguisher
•
•
•
•
Make sure there are still a few pieces of
dry ice into each group’s cup.
Demonstrate the procedure.
VSVS team members should light the
candles and stay with the students while
they do the next step. Do NOT leave a lit
candle unattended.
Tell the students to pick up the cup and
pour out the gas (CO2) into the cup over
the candle flame. This should extinguish
the candle. VSVS members should then
move to the next group.
Ask students: Why does CO2 extinguish
the candle? Why could we pour the CO2
into the cup? CO2 is heavier than air so it
will stay in the cup?
VI. Finish Demonstration of Freezing
Water with Dry Ice
• Remove the cup of water
from the container of dry
ice to illustrate how the
dry ice can freeze water.
• Have the students note
the phase changes.
Liquid water freezes to
solid ice water.
• Tell the students to look
at their thermometer
diagram to see that the
temperature of dry ice is
much colder that regular
ice.
VII. Review
• Review the changes of state and ask the students to
give examples from today’s experiments.
• What does sublime mean? A solid goes directly to a gas
without becoming a liquid.
• What is dry ice? Solid carbon dioxide.
• How cold is dry ice? -78°C. Refer to the thermometer
diagram.
• What happens when dry ice is dropped into water?
Bubble of carbon dioxide are given off, a cloud forms
above the water, the cloud stays in the container instead
of floating in the air, if any of the cloud falls out of the
container it floats down and disappears.