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Unit 2 Worksheet 1

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Unit 2 Worksheet 1
1. You decide to boil water to cook noodles. You place the pan of water on the stove
and turn on the burner.
a. How does the behavior of the water molecules change as the pan of water is
heated?
As the water is heated, the water molecules move faster and farther apart.
b. What about your answer to (a) would change if there were more water in the
pan?
The same phenomenon would occur but it would take longer because there are more
particles.
2. What property of matter best describes the way a typical alcohol thermometer
works? Explain (in terms of energy transfer) why the alcohol level in the
thermometer rises (or falls) when you place the thermometer in contact with both
warmer (or colder) objects.
Matter expands and contracts with changes in temperature because a change in thermal
energy causes the molecules to speed up (or slow down). When in contact with warmer
objects, energy from the surroundings is transferred to the alcohol molecules in the bulb of
the thermometer; as a result, they begin to move faster and father apart. This causes the
alcohol to expand and rise in the capillary. When the bulb is placed in contact with cooler
objects, energy is transferred from the alcohol to the surroundings; the molecules move
slower and closer together. The resulting contraction causes the level to fall in the
capillary.
3. If you feel feverish, why can't you take your own temperature with your hand?
In theory, all parts of your body are at roughly the same temperature; you can only really
detect differences in temperature.
Modeling Chemistry
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4. Your older brother announces that the lid to a jar of pickles from the refrigerator is
“impossible” to loosen. You take the jar, hold the lid under the hot water from your
sink’s faucet for a few seconds, and calmly open the jar. Your brother, when faced
with this blow to his pride, claims that he loosened it for you. What knowledge of
materials have you applied in this situation that really explains how you were able
to open the lid?
Heating the lid caused the molecules in the metal to move faster and move farther apart.
Thus, the lid became “larger” so it could be more easily removed from the jar.
5. Describe how Anders Celsius devised the temperature scale that bears his name.
Celsius used a tube of mercury, marking the height of the mercury column when he placed
the tube in an ice bath as 0В°C. When he placed the tube in a boiling water bath, he marked
the mercury column and called that 100В°C. He marked it linearly between 0 and 100В°.
6. Which would feel warmer to the touch - a bucket of water at 50ЛљC or a bathtub filled
with water at 25ЛљC? Which of these contains more energy? Account for any
differences in your answers to these questions.
The bucket of water will feel warmer because the average kinetic energy of the particles is
greater than those in the bathtub. However, since there are many more particles in the
bathtub, this water stores more energy.
Modeling Chemistry
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U2 ws 1 v3.0
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