Name
1.2 Act 2
Date
Pd
Hot and Cold
1. It has been proposed that water might be made out of very tiny particles that tend
to stick to each other. How are these small particles similar to tiny magnets?
The water particles stick together in a similar way like magnets do. Inone of our
labs we were able to drag a large drop of water through race track showing how
the water molecules stick together. In another lab we placed drops of water on
wax paper and they came together (combined) when dragged close to each
other.
2. Think back to when you touched a water droplet with a soapy toothpick. What
happened?
The water dome broke and the water quickly fell off the penny
Did the water still behave like small magnets?
No
Explain
The soap added to the water decreases the cohesion (attraction) between the
molecules so they do not stick together like they did before the soap is
introduced.
3. How does adding a droplet of food coloring or dye to a cup of water give evidence
that water particles are moving?
Explain.
After the drop of food coloring was added, you can see the color move
through the water. The water must be moving in order for the food coloring
molecules and water molecules to mix and spread.
©American Modeling Teachers Association 2014
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MSS Gr 6 U1.2 Act 2
4. The first frame below shows some food coloring (dye) particles that have just been
added to a cup of water. Fill in the next two diagrams to show what will happen to
the dye as time goes on.
5. Based upon your observations, are particles moving faster in cold water or in hot
water?
Particles are moving slower in cold water.
How do you know?
In the cold water, the colors drifted and slowly swirled and spread a bit but were
in streaks. The colors didn’t mix very much. In the hot water, the colors spread
more quickly and mixed together more than in the cold water.
6. Based on your observations and the animations, fill in the blanks with the words
increases or decreases.
Heating a substance ____increase_____________particle motion.
Cooling a substance _____ decrease___________particle motion.
As particle motion increases, the space between particles______ increase______
As particle motion decreases, the space between particles ______ decrease______
©American Modeling Teachers Association 2014
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MSS Gr 6 U1.2 Act 2
7. Using circles to represent water particles, draw a model of the particles in cold and
hot water.
 Use motion lines to show the speed of the particles.
 Consider the space between particles in each temperature of water.
Molecules in cold water are closer together and have fewer motion lines.
Molecules in hot water are further apart and have more motion lines.
8. Let’s say that you measure exactly 100 milliliters of water in a graduated cylinder.
You heat the water to 100 °C and notice that the volume increases to 104
milliliters.
Using what you know about the space between water particles and the way heating
affects particle motion; explain why the volume of water in the cylinder increases
when it is heated.
The volume of water increases when the water is heated because heating
makes the water molecules move faster. The extra speed of the molecules
competes with their attraction for one another and causes them to move
slightly further apart. Since the molecules move further apart, the same
amount of water takes up more room in the graduated cylinder.
©American Modeling Teachers Association 2014
3
MSS Gr 6 U1.2 Act 2