2-­‐1 Heat, Temperature and Conduction Name: Room temperature spoon placed in hot water. 1. Draw the cup of water and spoon before and after the spoon is placed inside. Draw circles for the molecules and motion lines. Before After 2. Explain, on the molecular level, how energy was transferred from the hot water to the room-­‐
temperature spoon. 3. In the experiments, why did the room-­‐temperature metal washers get warmer in hot water? Why did the water get colder? Hot spoon placed in room-­‐temperature water 4. Draw the cup of water and spoon before and after the spoon is placed inside. Draw circles for the molecules and motion lines. Before After 5. Explain, on the molecular level, how the heat was conducted from the hot spoon to the room-­‐
temperature water. ©2011 American Chemical Society 6. In the experiment, why did hot metal washers get cooler? Why did the water get warmer? Take it Further 7. Temperature is the measure of the average kinetic energy of the atoms of a substance. Does this mean that all of the molecules in a cup of water are moving at the same speed, or at a variety of speeds? Explain. 8. Explain why a substance such as metal feels colder than a substance such as wood, even though they are both at room temperature. 9. If you put a cup of cold water in one room and a cup of hot water in another room. Both rooms are the same temperature. Why does the cold water get warmer, and the hot water get cooler? ©2011 American Chemical Society 2-­‐2 Changing State – Evaporation Name: 1. Define evaporation, and give some examples. 2. Explain, on the molecular level, why room-­‐temperature water evaporates. 2. Explain, on the molecular level, why heating water increases the rate of evaporation. 3. Complete the diagrams of water evaporating. Use circles to represent water molecules, and add motion lines. 4. When water evaporates, do the water molecules themselves break apart, or do whole water molecules separate from each other? ©2011 American Chemical Society 2-­‐3 Changing State – Condensation Name: 1. Define condensation, and give some examples. 2. You saw an animation of water molecules as a gas condensing to form liquid water on the inside of the top cup. Since the water molecules were all separated as a gas, why did they come together to form a liquid? 3. Why do you think the cup with the ice has bigger drops of water on the inside than the cup without ice. 4. When you breathe on a cold window, or outside on a cold day, your breath makes “fog”. Using what you know about condensation, explain why you think the window gets foggy. 5. Using what you know about evaporation and condensation, explain what causes rain. ©2011 American Chemical Society 2-­‐4 Changing State – Freezing Name: 1. Complete the chart below to compare molecules in water and ice. Water Ice Speed of molecules Amount of movement Arrangement of molecules Distance between molecules 2. Write captions under the pictures to explain how the movement and position of molecules changes as the water freezes to become ice. 3. Why do different liquids have different freezing points? 4. Nitrogen is a gas at room temperature. It condenses to a liquid at -­‐196°C and freezes at -­‐210°C. Do you think the attraction between nitrogen molecules is strong or weak? Why? ©2011 American Chemical Society 2-­‐5 Changing State – Melting Name: 1. Where does energy come from to melt a piece of ice on a table? 2. Write a caption under each picture to explain how the motion and arrangement of the water molecules changes as ice melts. 3. In each box, draw molecules in the correct state. Use motion lines as needed. Label state changes with arrows. Solid Liquid Gas 3. How are the state changes of water similar to and different from state changes in most other substances? 4. Do regular ice and dry ice melt in the same way? Explain. 5. Dry ice sublimates very quickly in water. Why does it sublimate even faster in hot water? ©2011 American Chemical Society