Name Date Pd 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 1 U2 ws 1 v3.0 4. Your older brother announces that the lid to a jar of pickles from the refrigerator is вЂњimpossibleвЂќ to loosen. You take the jar, hold the lid under the hot water from your sinkвЂ™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 вЂњlargerвЂќ 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 2 U2 ws 1 v3.0