ACCEL: PATTERNS OF MASS AND DENSITY IN THE SOLAR SYSTEM Name: Date: Purpose: To investigate the patterns of mass, density, and size of planets in the solar system and compare the terrestrial and giant planets. Background: Mass is a measure of the amount of matter an object contains. The masses of the planets on the Planet Data Table are given in relation to Earth s mass. For example, mercury s mass is given as 0.056, which means that it contains only a small fraction of the matter that Earth contains. On the other hand, the giant planets contain several times more matter than Earth. Density is the amount of matter in a given amount of space, or the mass per unit volume of a substance. The average densities on the Planet Data Table are expressed in grams per cubic centimeter (g/cm 3 ). For density, the density of pure water is approximately 1 g/cm 3. Hypothesis: What relationship do you think you will observe between the mass, density, and size of planets. Procedure: Refer to the Planet Data Table handout to find the information needed to answer the following questions. Answer in complete sentences unless answer is a fill-in. 1. The planet is the most massive planet in the solar system. It is times more massive than Earth. 2. The least massive planet (excluding Pluto) is, which contains only as much mass as Earth. 3. How many times more massive than Mercury is Jupiter? times The gravitational attraction of a planet is directly related to its mass. In other words, as a planet s mass increases, its gravitational attraction increases. Your weight is a function of the gravitational attraction of an object acting on your mass. 4. Which planet exerts the greatest pull of gravity? Explain your answer. 5. On which planet would you weigh the least? Explain your answer. 6. Which of the two groups of planets: terrestrial or giant, would have the greatest ability to hold large quantities of gas as part of their composition? Explain your answer. 7. Write a general statement comparing the masses of the terrestrial planets to the masses of the giant planets.
8. Plot a point on the graph below for each planet (excluding Pluto). The point should be plotted where the planet s diameter intersects its density. Use the diameter measurements in kilometers from the Planet Data Table. Label each point with the planet s name. Use a different color for the terrestrial planets and the giant planets. Give the graph a title and include a key. 150 DIAMETER (km X 0) 50 0 0 1.0 2.0 3.0 4.0 5.0 6.0 DENSITY (g/cm 3 ) 9. What general relationship exists between a planet s diameter and its density? Circle your answers for the next two questions. 10. The densities of the two rock types that form the majority of Earth s surface, the igneous rocks granite and basalt, are each about 3.0 g/cm 3. The average densities of the terrestrial planets are (greater than, less than) the density of Earth s surface rocks. The average densities of the giant planets are (greater than, less than) the density of Earth s surface rocks. 11. The term (rocky/gaseous) best describes the terrestrial planets. 12. The average density of Earth is about 5.5 g/cm 3. Considering that the densities of Earth s surface rocks are much less than Earth s average density, you could infer that the center of the Earth is made of (rock/gas) that is (more than /less than) 5.5g/cm 3. 13. Which of the planets has a density less than water and could therefore float (if you could find a large enough container!)?
14. Explain why it is possible for Jupiter to be such a massive object and yet have such a low density. 15. Write a general statement comparing the densities of the terrestrial planets to the densities of the giant planets. 16. Why are the densities of the terrestrial and giant planets so different? 17. Examine the estimated mass, diameter and density of Pluto. Complete the following statements by circling the correct response. The mass of Pluto is most like the masses of the (terrestrial, giant) planets, while the density is similar to that of the (terrestrial, giant) planets. This suggests that Pluto is a (small, large) body made of (rock, ice and frozen gas). 17. Pluto makes up the Kuiper belt. What do you think the other objects in the Kuiper belt would be like in terms of density and composition (use the data in the chart and the patterns seen to support your statement)? 18. If the material in the asteroid belt (2.8AU) had coalesced to form a planet, what do you think it would have been like in terms of density and compostion? Would it likely have become a terrestrial planet or a Jovian planet? Explain your reasoning OTHER PATTERNS IN THE SOLAR SYSTEM Use the information in the Planet Data Table to explore some of the other relationships between the planets. 19. Describe the relationship between: (a) distance from the sun and a planet s period of revolution (b) distance from the sun and a planet s orbital velocity. 20. Describe the relationship between the number of moons (satellites) a planet has and (a) its mass. (b) its general distance from the sun. 21. How do the patterns you see between inner and outer planets fit in with the Nebular Hypothesis?What accounts for their differences?
PART 2 Density of Moons We know that rocks have an average density of 3.5g/cm 3 and ice has a density of 0.9 g/cm 3. We can calculate the density of a moon by using the following formula: (3.5 x percentage of rock) + (0.9 x percentage of ice) = density Scientists can estimate the mass of something by its gravitational pull and they can estimate its size using techniques like angular size. From this we can determine a density of objects in space. If we wanted to know the percentage that was ice or rock we would need to use the formula above except the problem is that there are now two unknowns (both the % ice AND the % rock). However because the two together must equal %, we can assume that the percentage of 1ce is always equal to minus % rock. So we can rewrite the equation as follows: (3.5 x % rock) + (0.9 x ( - %rock) = density Now you can simply solve for the % rock to figure out the portion of the objects density that is ice versus that which is water. 1. Use this formula to determine the % of rock for Jupiter s moon Callisto, which has a density of 1.8g/cm 3 Show your calculations and circle your answer. 2. What would be the % ice for Callisto? When dealing with lots of moons its is easiest to make a graph since there is a relationship between the % of rock and % ice and the density. Use the formula to complete the chart: (3.5 x percentage of rock) + (0.9 x percentage of ice) = density Percent rock Percent Ice Density of moon g/cm3 0 3.5 80 20 60 40 40 60 20 80 0 Make a line graph on the next page of the density of moon vs. the percent Rock. Give it a title.
DENSITY OF MOON 3.0 2.0 1.0 % ROCK 1. Jupiter s moon Ganymede has a density of 1.9 g/cm3. Based on your graph what percentage of it is rock? 2. Neptune s moon Triton has a density of 2.1 g/cm3 and would therefore be % rock. 3. Jupiter s moon Europa has a density of 3.0g/cm3. What is its % of rock? 4. How do you think the rock and ice is distributed inside the moons? Give the reason for your answer.