Name: Date: Student Exploration: Boyle’s Law and Charles’s Law Vocabulary: absolute zero, Boyle’s law, Charles’s law, Gay-Lussac’s law, Kelvin
... [Show More] scale, pressure Prior Knowle dge Question (Do this BEFORE using the Gizmo.) A small helium tank measures about two feet (60 cm) high. Yet it can fill over 50 balloons! How can such a small tank contain enough helium to fill so many balloons? The pressure inside the tank is being compressed until the little lever is opened that’s when it will be able to fill up with helium and air. Gizmo W arm -up The Boyle’s Law and Charles ’s Law Gizmo shows a container of gas. Inside , small purple spheres represent gas molecules. 1. Observe the particles. Are the y all moving at the same speed? Looks like they are going at the same speed. How do the particles interact with the walls and lid of the container? They bounce right off the lid and walls and continue to move around. These interactions contribute to the pressure on the walls of the container. Pressure is defined as force per unit area. The SI units of pressure are newtons per square meter (N/m2), or pascals (Pa). 2. Slowly drag the temperature (T) slider back and forth. (Note: In this Gizmo, the Kelvin scale is used to measure temperature. On the Kelvin scale, 0 degrees is absolute zero, the coldest possible temperature. Absolute zero is equal to -273.15 °C or -459.67 °F) A. How does the change in temperature affect the speed of the molecules? The colder it gets the slower the molecules move. B. How does the change in temperature affect the volume of the container? The change in temperature causes the volume to decrease 2018 Question: How does pressure affect the volume of a gas? 1. Form hypothesis: In this experiment, you will pile weights on the lid of the container of gas. What do you think will happen as more weight is added to the lid? The more weight that is added then the smaller the volume gets. 2. Notice: Look at the DESCRIPTION pane. What is the mass of the lid? How much pressure does the lid exert on the gas? 245.25n/m^2 3. Collect data: With the temperature held constant at 300 K, use the Select mass slider to place weights on the lid. Record the pressure and volume of the gas for each added mass. Added mass on the lid Total mass (lid + added mass) Pressure* Volume 0 kg 10 kg 98.1n/m^2 2.54m^3 10 kg 20 kg 196.2n/m^2 1.27m^3 20 kg 30 kg 294.3n/m^2 0.85m^3 30 kg 40 kg 392.4n/m^2 0.64m^3 *This model does not include atmospheric pressure, which is 101,325 N/m2. (continued from previous page) the gas? It slowly decreases as the temperature increases. This relationship is called Boyle’s law. 5. Calculate: Compare the pressure and volume values in your data table. A. How did doubling the pressure change the gas volume? It made it decrease some. B. How did tripling the pressure change the gas volume? Made the volume decrease even more. C. How did quadrupling the pressure change the gas volume? It made it decrease the most. (Activity A continued Activity A 6. Predict: If the added mass on the lid was 50 kg, a total mass of 60 kg would exert pressure on the gas inside the container. What will be the volume of the gas? It would be small, and the molecules would be moving quicker. The volume will be small and will decrease as more weight is placed. 7. Test: Test your prediction using the Gizmo. What is the volume of the gas? 0.42m^3 Was your prediction correct? Yes 8. Create a graph: On the GRAPH tab, select V vs. P. Set m to 0 kg, and click Record to plot a point on the graph. Plot a point for each possible mass to create a graph showing the relationship between pressure and volume. When your graph is completed, click the camera ( ) icon to take a snapshot. Right-click the image, and click Copy Image. Paste the image into a blank word-processing document, and label the graph “Volume vs. Pressure.” A. What is the shape of the graph? The graph is increasing so does the other. B. How does this graph illustrate Boyle’s law? When one increases so does the other. C. How do you think the graph might change if the higher temperature, say 400 K? The graph might be longer but the volume would also increase along with the temperature. 9. Apply: Think about a small helium tank that can fill 50 balloons. What must be true about the helium in the tank compared to the helium in the balloons? Helium is contained in a metal container so that means it compresses more when it is in a flexible balloon. Activity B: Charles’s law Get the Gizmo ready: □ On the SIMULATION pane, set T to 100 K and m to 0 kg. Question: How does temperature affect the volume of a gas? 1. Form hypothesis: How do you think the volume of a gas will change as the temperature rises and falls? I think that the temperature and volume is going to increase. 2. Collect data: Without changing the mass on the lid, record the pressure and volume of the gas at each of the given temperatures. Temperature Pressure* Volume 100 K 98.1n/m^2 0.85m^3 200 K 98.1n/m^2 1.7m^3 300 K 98.1n/m^2 2.54m^3 400 K 98.1n/m^2 3.39m^3 500 K 98.1n/m^2 4.24m^3 *This model does not include atmospheric pressure, which is 101,325 N/m2. 3. Analyze: As the temperature increases at constant pressure, what happens to the volume of the gas? The volume of the gas continues to increase. This relationship is called Charles’s law. (continued from previous page) 4. Explain: Based on the motions of the gas molecules, why do you think the volume changed as it did when the temperature was increased? The reason the volume increased is because the lid was lifted with the heat so it made it easier for the gas particles to move around. 5. Think about it: Why do you think the pressure was the same in each test? There was not a change in amount of particles hence the reason why the pressure stayed the same (Activity B continued Activity B 6. Calculate: Compare the pressure and volume values in your data table. A. How did doubling the temperature affect the gas volume? It would make the volume increase double its volume. B. How did tripling the temperature affect the gas volume? It would make it triple the value of the volume, C. How did quadrupling the temperature affect the gas volume? It would make it quadruple the value of the volume. 7. Predict: Suppose the temperature was 50 K. What will be the volume of the gas? The volume of the gas would be increasing at small amount. 8. Test: Test your prediction using the Gizmo. What is the volume of the gas? Was your prediction correct? Yes 9. Create a graph: On the GRAPH tab, select V vs. T. Set T to 50 K, and click Record to plot a point on the graph. Plot a point every 50 degrees to create a graph showing the relationship between temperature and volume. When your graph is complete, click the camera icon to take a snapshot. Paste the image into your document, and label the graph “Volume vs. Temperature.” A. What is the shape of the graph? The graph is increasing B. How does this graph illustrate Charles’s law? The volume is increasing and the temperature increases with it. 10. Apply: Based on what you learned, what would happen to a balloon placed in the freezer? The balloon shrinks. What would happen to a balloon placed in a warm oven? (Assume it doesn’t pop.) The balloon continues to expand in size. 11. Think and discuss: Consider temperature, pressure, and volume. How does the mathematical relationship in Boyle’s law compare to that in Charles’s law? They both work and both of them also go up. Question: How does temperature affect the pressure of a gas when volume is constant? 1. Form hypothesis: If the volume of a gas is held constant, how do you think the pressure will change as temperature increases? The pressure will decrease the hotter it gets. 2. Collect data: Select the TABLE tab. Record the pressure when T = 100 K, 200 K, and so forth up to 500 K. (Note: The volume will remain constant at 1.02 m3.) Temperature Pressure Pressure Temperature 100 K 81.75n/m^2 0.8175 200 K 163.5n/m^2 0.8175 300 K 245.25n/m^2 0.8175 400 K 327n/m^2 0.8175 500 K 408.75n/m^2 0.8175 3. Analyze: Divide the pressure by the temperature to fill in the last column of the table. Since 1 N/m2 is equal to 1 pascal (Pa), write the units of the ratio as Pa/K. A. When the volume is held constant, how does the pressure change as temperature increases? The pressure would increase by 81.75n/m^2 every 100K. B. What do you notice about the ratio of pressure to temperature, when volume is constant? Its consistent and it’s a direct ratio with each other. (continued from previous page) Gay-Lussac’s law states that, at constant volume, the ratio of pressure to temperature is constant. As temperature increases, pressure increases as well. 4. Explain: Based on the motions of the gas molecules, why do you think the pressure changed as it did when the temperature was increased? The pressure increased because the speed of the molecules hit the walls quicker. (Activity C continued Activity C 5. Calculate: Compare the pressure and temperature values in your data table. A. At constant volume, how did doubling the temperature affect the pressure? It increased the pressure by 81.75n/m^2 B. How did tripling the temperature affect the pressure ? It increased the pressure by 81.75n/m^2 times 2 C. How did quadrupling the temp erature affect the gas pressure ? 1. Create a graph: Record the pressure for temperatures of 50 K, 150 K, 250 K, 350 K, and 450 K. On the GRAPH tab, select P vs. T. Click the camera icon to take a snapshot. Paste the image into your document, and label the graph “Pressure vs. Temperature.” A. What is the shape of the graph? Increasing and going upwards B. How does this graph illustrate Gay-Lussac’s law? It doubles the original number. 2. Apply: Based on what you learned, what do you think would happen if you placed a sealed container of gas into a fire? I think it will pop or get bigger. 3. Challenge: Combine Boyle’s law, Charles’s law, and Gay-Lussac’s law into a single proportional relationship between pressure (P), volume (V), and temperature (T). Use the symbol “ ” to represent “is proportional to.” Explain your reasoning. All of the laws have the same variables. Show Less [Show Less]
