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Lesson Two: Iceberg Ahead: How does temperature affect the density of water?

SUBJECT: Comprehensive Science

OVERALL TIME ESTIMATE: 1, 50 minute period

LEARNING STYLES: Visual, auditory, and kinesthetic

VOCABULARY: Density

LESSON SUMMARY: Students will discover how temperature affects water
density through a use of a movie and demonstration, and participation in an inquiry
based lab.

STUDENT LEARNING OBJECTIVES:
1.) The students will be able to define density (SC.A.1.3).
2.) The students will be able to explain why and how temperature affects
density (SC.H.1.3).

MATERIALS:
For Demonstration (1 set needed for instructor each period)
- An ice cube made with blue food coloring added
- 1 beaker of room temperature water with yellow food coloring added
- A copy of the movie “Titanic”
- An overhead of an iceberg from
http://www.grow.arizona.edu/images/water/iceberg.jpg

For Lab (1 set needed for each lab group)
- Labeled beakers with the following:
o 1 beaker half full of cold water with a drop blue food coloring
o 1 beaker half full of hot water (near boiling) with a drop of yellow
o 2 beakers half full of room temperature water - one with yellow
food coloring, the other with blue food coloring
- 1 Straw
- Heat shield gloves or oven mitts
For each student
- Journal to record observations and results

- Make ice the night before by adding blue food coloring to ice tray.
- Before class starts heat water in a large beaker to almost boiling, and
add yellow food coloring. Once it has reached its desired heat divide
between lab groups.
- Add yellow food coloring to one large beaker of room temperature water.
Add blue food coloring to another large beaker of room temperature
water. Divide between lab groups.
- Cue “Titanic the movie to the portion where the ship runs into the
iceberg.
- Prepare overheads described in materials.

PROCEDURE:
Demonstration/Introduction (10 minutes)
- Show students the portion of the “Titanic” movie where the ship sinks. If
you don’t have the movie, instead ask them if they have seen the movie
and if they know what happened to the ship. It sank on its maiden
voyage.
-   What caused the ship to sink? It ran into an iceberg creating a hole
below the water line which caused the ship to sink.
-   Show overhead of the iceberg.
-   Why did the captain of the ship did not see the iceberg? The captain did
not see the iceberg until it was too late because the accident occurred at
night and 90% of an iceberg is below the water line. Tell students that
the iceberg is still floating even though 90% of it is below water due to
the density of ice.
-   To demonstrate, float a blue colored ice cube in the hot water that is
dyed yellow. Notice that the ice cube floats but melts rapidly.
-   Tell students that as the ice melts the cold water begins to move to the
bottom causing mixing to occur which is characterized by the green layer
between the yellow on top and the blue on the bottom. Ask students to
record their observations in their journals.
-   What causes ice to float and why did the melted portion go to the
bottom of the beaker? Do not give an answer. Tell students that you
have prepared a lab that will hopefully help demonstrate what causes this
even to happen.

Lab (30 minutes)
-   Divide students into groups of four or five, with each student assigned a
specific role (recorder, equipment manager, manager, etc.)
-   Once students have settled down in their lab stations, tell them to
proceed with the first part of the lab.
-   Combine the two beakers that contain the room temperature water by
gently pouring one into the other. Record observations in journal. You
will find that it makes a green color in the entirety of the beaker.
-   Using oven mitts, add the contents of one beaker of hot water (yellow) to
the beaker containing the cold water (blue) by gently pouring the hot
water into the cold, and allowing the hot water to flow over cold water.
Record observations in journal. The colors stay separate with the yellow
on top of the blue, and a thin green layer in the middle beginning to
appear over time.
-   Allow all groups to finish the first portion.
-   Why do you think the above phenomena are occurring? After fielding
possible answers, tell them the next experiment may help them
determine what is happening.
-   Proceed with the second portion of the lab.
-   Each lab station has one cold water beaker (blue), one hot water beaker
(yellow) and one straw.
-   Use the straw to pick up water by putting the straw into one of the
beakers, then placing a finger tip over the straw’s opening. When you lift
the straw above the surface, the water should stay in the straw. Put the
straw in the other beaker, along its edge, and slowly release. You will
find that it will go to the bottom and hardly mix with the hot water.
Record observations in journal. If the students put the cold water into
the hot water then the cold water will stay toward the bottom and yellow
should be on top of blue. If the students put the hot water into the cold
water then the hot water will move toward the top causing a mixing
effect resulting in blue on the bottom, green in the middle and small
amount yellow on top, if at all.

Wrap-Up (10 minutes)
- Compare results. Either by group or as a class.
- What is happening? The water is separating out into layers and or mixing.
- Why does this occur? The temperature of the water affects its density.
- Define density. The mass of an object of matter divided by its volume or
how much space it takes up.
-   What form of water is most dense and why? At this point most students
will answer that ice is most dense since it is a solid, but in fact it is one
of the least. If they answer this way, ask students if they have ever put
a coke can in the freezer. Usually you will have a few that have. Ask
them what happened. Most will tell you that it froze and exploded. At
this point tell them that the coke indeed froze, but also expanded, and
thus needed more space than the can had inside of it. Then remind them
of the formula for density, d = m/v. If the volume of something
increases (in this illustration the coke in the freezer), then what happens
to the density? It decreases. Thus since ice expands and takes up more
space, it is less dense than other water. The correct answer is the cold
water (blue) that is not frozen.
-   How does temperature affect the density of water? Remember the
iceberg and what happened when hot mixed with cold water.
-   Think about it overnight and research it online if they want.

ACKNOWLEDGMENTS:
This demonstration was adapted from:
Project Wet Curriculum and Activity Guide
Council for Environmental Education
5555 Morningside, Suite 212
Houston, TX 77005-3216

SUNSHINE STATE STANDARDS:
SC.A.1.3 – The student understands that all mater has observable and measurable
properties

SC.D.1.3 – The student recognizes that processes in the lithosphere, atmosphere,
hydrosphere, and biosphere interact to shape the Earth.

SC.D.2.3 – The student understands the need for protection of the natural systems
on Earth.

SC.G.1.3 – The student understands the competitive, independent, cyclic nature of
living things in the environment

SC.H.1.3 – The student uses the scientific processes and habits of mind to solve
problems.

SC.H.2.3 – The student understands that most natural events occur in
comprehensible, consistent patterns.

SC.H.3.3 – The student understands that science, technology, and society are
interwoven and interdependent.

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