Density by Jodye Selco

Transcription

1 Density by Jodye Selco What is density? Examine the objects (cubes) that are in front of your group. 1. How are these objects the same? 2. How are they different? 3. Rank from most dense to least dense 4. What do you think would happen to the mass if the size were doubled? What happens to the density? What happens to the mass if bar is cut in half; what about the density? 1

2 5. Draw pictures of the atoms inside the least dense metal and the most dense metal. Explain why you drew your pictures this way. Least dense Most dense 6. List the factors you think contribute to making one metal more dense than another. 7. Examine the equal mass cubes. How are these the same? Different? Do you believe that their masses are the same? 8. Now examine the equal mass rods. How are these the same? Different? Do you believe that their masses are the same? 9. Describe the ways you can use the equal mass rods and cubes and equal volume cubes to help your students understand fractions. 10. Write an explanation of density for your students that they would understand. 2

3 Density Tower: When two substances are placed in the same container, the more dense substance will sink to the bottom. This is because its weight or mass is more concentrated into a smaller volume. As long as the liquids do not mix, the denser one will displace the less dense liquid. The density of each substance known is different because this physical property depends on both the types of atoms that make up the substance and how they pack together. 1. Cover your work surface with a layer of paper. 2. Pour about 1 inch of water into a cup. Add 1 drop of blue food coloring. Describe what you see and/or the physical properties you observed. 3. Pour about 1 inch of corn syrup into a cup. Describe what you see and/or the physical properties you observed. 4. Pour about 1 inch of oil into another cup. Add 1 drop of yellow food coloring. Stir. Describe what you see and/or the physical properties you observed. 5. Make a prediction: based on your observations of these three liquids, which do you think is the most dense and least dense? Explain your choices. 6. If all three liquids were added to the same cup, do you think they will mix or that layers will form? 7. If layers were to form, which liquid would be on the bottom and which would be on the top? Why? 8. Now add the water to the oil; then add the corn syrup to the same cup. Draw and label a picture representing the liquids in your cup. Did anything mix without stirring? Which parts? 9. What property/properties of oil causes it to be the top layer? 3

4 10. Which liquid do you think is the densest? Why? 11. Obtain several items; write down what they are. Predict the relative density of each item. 12. Predict (by drawing) where they will end up in your density tower. 13. Now, drop the items into your density column. Were your predictions correct? If not, what did happen? 14. What can you say about the densities of these objects relative to the liquids? 15. Equal amounts of Karo syrup (density 1.2 g/ml), colored water (density 1.0 g/ml) and vegetable oil (density 0.8 g/ml) are poured into a tall cylinder. Draw a picture of the result. The objects listed below are then added to the density tower. Show clearly on your drawing where they end up. a) marble (density 2.5 g/ml) b) ice cube (density 0.94 g/ml) c) rubber ball (density 1.1 g/ml) d) wood block (density 0.6 g/ml) 16. If a denser solid is placed on top of a less dense solid, there is no movement. Yet, when a more dense liquid is added to a less dense liquid, it passed through the less dense liquid on its way to the bottom. Which physical property/properties is responsible for this behavior difference between solids and liquids? 4

5 DENSITY Sentence Frames (by Mary Bruno, Kordyak Elementary School, Rialto USD) 1. is denser than. 2. has less density than. 3. is more dense than, but less dense than. 4. has\less density than, but is more dense than. 5. is less dense than, and. 6. has more density than, and. 7. has more density than, because sits below in the density tower. 8. is less dense than because sits above in the density tower. 9. has density than because sits in the density tower. 10. If sits in the middle of a water layer then its density is the density of the water. 11. I know is less/more dense than because. 12. has density than because. 13. The layer is on the, where the layer is, therefore has density than. 5