Lesson 2 Reading One – Why Does Conduction Matter? (p. 41-42 - ES2)
1. In the lab where you heated the end of a metal rod and saw that the fat balls fell of the rod in the order of those closest to the source of the heat, what evidence does this provide about the heat transfer? It is evidence that the heat was transferred from one end to the other. You learned that this is called conduction.
2. Explain why is it that if you put a metal pan on the stove, even though the heat is under the pan, the metal handle on the pan can become very hot. By conduction, the heat is transferred from the bottom of the pan to the end of the handle.
Conduction and Your Food
3. Using what you know about conduction, explain how an egg gets hard-boiled. The burner transfers energy to the pan. That is conduction. The thermal energy from the pan is transferred to the water. Because the eggs are in contact with the water, thermal energy is transferred to them by conduction.
4. Draw an illustration of your response in #3 (about how an egg gets hard-boiled by way of conduction). Label all parts of your drawing.
(Answers will vary)
5. Why does an egg that was boiled in hot water form into something solid that you can hold in your hand? When the proteins of a raw, liquid egg come into contact with heat, it causes them to change form. When you increase the temperature of the food, you increase the speed of the molecules in a food. The greater their speed, the more they collide. These collisions between the molecules can lead to changes in molecular structures by creating new molecules. These collisions break apart the protein molecules and create new molecules. These new molecules have different characteristic colors, flavors, and textures from the original molecules. The formation of new molecules is called a chemical reaction.
6. What are proteins? Proteins are molecules that make up a large part of most living things, and it is important for us to eat proteins as part of our diet.
7. How is conduction related to the movement of molecules inside of objects? As the molecules move faster, the object has more thermal energy. Those fast moving molecules bump into others and make them move faster. So that is what happens inside the egg. As the molecules in the egg white start to move faster, some of their energy gets transferred to the yolk. As they all move faster, the thermal energy inside of the egg increases and cooks the egg all the way to the yolk.
8. Use what you know about conduction to draw a diagram that explains what is happening in this image (of the hand holding an ice cube that is melting). The energy moves from where it is warmer to where it is cooler, then your diagram should show the heat being transferred from the hand to the ice cube by conduction. As more thermal energy is transferred from the hand to the ice cube, it melts.
9. How does all of this relate to weather? Air at the surface of the Earth is heated from below by conduction. The energy is transferred to the air and the thermal energy of the air increases.
10. What is temperature? Temperature measures the thermal energy of an object.