Gas Laws Gas Laws: Gases and pressures affect our lives every day. From the weather we experience to the air we breathe, it all has to do with gases and pressures. Why do we have wind? Why do we have the weather systems we do? How come we are not crushed by the weight of the atmosphere pushing down on us? How are we able to drink through a straw? All of these questions and more can be answered by taking a close look at the gas laws. Weather systems and air constantly want to move from an area of higher concentration to an area of lower concentration. With this knowledge, we can evaluate our ability to drink through straws. It is NOT a sucking action that draws the fluid up the straw; it is a change in pressure. Throughout this unit we will look at the various gas laws that are responsible for many of the natural occurrences that happen in our lives. We will also make calculations to predict how much gas may or may not be present. We will conclude with the ideal gas law that allows us to tie stoichiometry into the gases as well. Ideal Made of small particles that have MASS Gases are mostly empty space Low density Gas particles are in constant, random straight line motion There are NO attractive or repulsive forces between particles Particles have NO volume Collisions are ELASTIC (no loss in total kinetic energy) Ideal vs. Real Gases Real Same as Ideal Same as Ideal Same as ideal Same as ideal There are VERY SMALL attractive and repulsive forces between particles Particles have a very small volume Collisions are inelastic (NOT elastic) (When gas particles collide they will lose energy) All the videos will be posted on YouTube and can be accessed using multiple sources. The videos have been formatted to work on iphones, ipads, Android phones, Kindles, and Nooks. Titles of the videos to search are listed below, and the creator of the videos should be NRHSChemistry. Lesson Target(s) for Each Video: Video 1 Got Gas? I can distinguish between an ideal and a real gas. I can apply the kinetic theory to the movement of gas molecules. Video 2 Boyle s Law I can apply Boyle s Law to the behavior of gases. Video 3 Charles Law I can apply Charles Law to the behavior of gases. Video 4 Gay-Lussac s Law I can apply Gay-Lussac s Law to the behavior of gases. Video 5 Combined Gas Law I can apply the combined gas law to calculations involving gases. Video 6 Dalton s Law of Partial Pressure I can calculate the partial pressure of gases. Video 7 Ideal Gas Law I can apply PV=nRT to a gas and calculate the number of moles, liters, pressure, or temperature of said gas. Essential Learning Outcomes: 1. Change can be measured. 2. Changes can occur within a substance that alters its identity.
Required activities: Due dates are in parentheses Gas Laws P.S. 1-9 (4/27) o Video 1 Got Gas? (4/24) Gas Laws P.S. 10-18 (5/2) o Video 2 Boyle s Law (4/25) o Video 3 Charles Law (4/25) o Video 4 Gay-Lussac s Law (4/25) Gas Laws P.S. 19-23 (5/3) o Video 5 Combined Gas Law (4/26) o Video 6 Dalton s Law of P. P. (4/27) Gas Laws P.S. 24-28 (5/4) o Video 7 Ideal Gas Law (5/1) The Crushing Can Lab (4/25 to 4/28) o Peer Review of Report (5/1) o Lab Report (5/4) Gas Law Unit Quest (5/5) Boyle s Law Important Vocabulary Charles s Law Combined gas law Dalton s law of partial pressure Gay-Lussac s Law Ideal gas law Kinetic theory Partial pressure Additional Resources: iphone and ipad apps: None that I could find.if you find one and feel it is useful, please let me know!!!
Chemistry Name: Problems and Questions Gas Laws Hour: Directions: Answer the following questions using complete sentences when necessary. On numerical problems, show all work, circle your answers, and follow all rules of significant figures for full credit. 1. How can you raise the average kinetic energy of a glass of water? 2. Thoroughly explain the assumptions of the kinetic theory of gases. 3. Convert the following measurements: a) 345 mmhg to atmospheres b) 986 kpa to atmospheres c) 675 kpa to mmhg d) 34.5 o C to K e) 456 K to o C 4. Explain how liquids differ from gases in (a) physical state and (b) compressibility. 5. How can you get water to boil at around room temperature (23 C)? Explain why this happens. 6. In Torricelli's barometer, the barometer with mercury in the dish, why doesn't the mercury fall back down the tube into the dish? 7. Why does a liquid rise in the straw when your drink a soda? Be very specific. 8. Explain the difference between a real gas and an ideal gas. 9. If a liquid only half as dense as mercury were used in a barometer, how high would its level be on a day of normal atmospheric pressure? Explain. 10. 1.42L of oxygen gas is at a pressure of 235 kpa. When the pressure is changed to 345 kpa, what will happen to the volume of the gas if the temperature stays constant? 11. A 425 ml sample of O 2 gas was collected at 742.3 mmhg. What would be the pressure in mmhg if this gas was allowed to expand to 975 ml at constant temperature? 12. What happens to the volume of a balloon filled with 0.357 L of hydrogen gas collected at 741.3 mmhg when the atmospheric pressure increases to 758.1 mmhg? 13. What is the volume of a scuba tank if it takes 2000. L of air collected at 1.00 atm to fill the tank to a pressure of 150. atm? 14. A gas is compressed at constant pressure at 34.5 C from 27.0 L to 3.00 L. What will happen to the temperature of the gas? 15. 6.78L of a gas is kept under a constant pressure. Its temperature is increased from 40.0 C to 140. C. What will be the change in volume? 16. A 5.00 L balloon has a temperature change from 23.3 C to -124 C, what will be the new volume of the balloon. 17. The temperature of 15,250mL of a gas is decreased from 25.0 C to -25.0 C. What will be the change on the volume of the gas if the pressure of the gas remains the same? 18. Explain how Charles' experiments with gases indicated the possible location of an absolute zero. 19. A gas under a pressure of 3.54 atm is heated form 0.00 C to 95.0 C. What will the new pressure be?
20. A sealed aerosol canister with a pressure of 2.00 atm is thrown into a bonfire. The canister is rated for 15.0 atm of pressure. The temperature of the canister increases from 25.0 C to 550 C. Will the canister burst? Support your answer. 21. A 5.00 L air sample at a temperature of -50.0 C has a pressure of 800. mmhg. What will be the new pressure if the temperature is raised to 100. C and the volume expands to 7.00 L? 22. A 5.00 L air sample at a temperature of -75.0 C has a pressure of 760. mmhg. What will be the new temperature in degrees Celsius if the pressure on the gas is raised to 850. mmhg and the volume is raised to 8.00 L? 23. 23. A gas mixture containing oxygen, nitrogen, and carbon dioxide has a pressure of 250. mmhg. If P O2 = 50.0 mmhg, P N2 = 175 mmhg what is the partial pressure of CO 2? 24. A gas mixture of argon, nitrogen and carbon monoxide gas has a pressure of 3.44 atm. If the partial pressure of argon is 654 mmhg and the partial pressure of nitrogen is 175 kpa, what is partial pressure of carbon monoxide in atmospheres? 25. Calculate the volume of a balloon that could be filled with 1.25 moles of helium that has a pressure of 200. atm at 25.0 C? 26. Calculate the number of liters occupied by each gas at 35.0 C and 1.33atm. a) 2.50 mol N 2 b) 0.600g H 2 c) 12.3g O 2 27. What pressure will be exerted in millimeters of mercury if 12.0g of oxygen gas at 25.0 C and has a volume of 0.650 L? 28. Determine the volume occupied by 32.5g of sulfur dioxide gas at 15.0 C if the pressure is 622 mmhg.
Lab 6: Pressure, Temperature, and Volume of Gases: How Does Changing the Volume or Temperature of a Gas Affect the Pressure of That Gas?? Introduction There are three states of matter: solid, liquid, and gas. Each state of matter has physical properties that distinguish it from the other states; for example, matter in the solid phase has a definite shape, whereas matter in a liquid or gas phase will take on the shape of its container. The physical properties associated with the state of matter allow us to predict how different substances may react under various conditions. Particles in a gas move about more freely than those in a solid or liquid and therefore react to changes in temperature and pressure in a manner that is different than solids or liquids. The volume of a sample of gas, or the amount of space that a sample of gas occupies, is particularly influenced by a variety of factors such as temperature or pressure. Just like the shape of a sample of gas or liquid is determined by its container, the volume of a sample of gas is influenced by its surroundings. A small sample of gas, like air, may be confined to a small container such as a balloon, or if the balloon pops the sample of gas can expand to occupy the entire volume of a classroom. Consider a tank of helium gas used to fill birthday balloons. There is a large amount of gas stored inside the tank, but several birthday balloons filled with a sample of the gas can easily expand to a size much larger than the tank. Understanding the physical properties of gases and how a gas interacts with its surroundings helps to explain this phenomenon. In this investigation you will explore the relationship between volume, temperature, and pressure for a gas within a closed system. Your Task Determine how changes to the volume and the temperature of a gas within a closed system affect the pressure of that gas. Then develop a general mathematical model that can be used to apply and describe these relationships with respect to all gases. The guiding question of this investigation is, How does changing the volume or temperature of a gas affect the pressure of that gas? Materials You may use any of the following materials during your investigation: Consumables Equipment Ice Gas pressure sensor Temperature sensor Sensor interface Syringe Erlenmeyer flask Single hole rubber stopper Rubber tubing Beaker (500 ml) Hot plate Safety Precautions Follow all normal lab safety rules. In addition, take the following safety precautions: Wear indirectly vented chemical-splash goggles Use caution when working with hot plates because they can burn skin. Hot plates also need to be kept away from water and other liquids. Handle all glassware (including thermometers) with care. Wash your hands with soap and water before leaving the laboratory. Investigation Proposal Required? Yes No
Getting Started To determine the relationship between the pressure, the volume, and the temperature of a gas, you will need to set up an apparatus that will allow you to first measure changes in gas pressure when the volume of gas changes. This can be accomplished with the apparatus shown in Figure L6.1. You will then need to be able to measure changes in gas pressure when the temperature of the gas changes. This can be accomplished with the apparatus shown in Figure L6.2. Once you have set up these apparatuses, you must determine what type of data you need to collect, how you will collect the data, and how you will analyze the data. To determine what type of data you need to collect, think about the following questions: o What type of measurements or observations will you need to record during each experiment? o When will you need to make these measurements or observations? To determine how you will collect the data, think about the following questions: o What will serve as your dependent variables? o What will serve as a control (or comparison) condition? o What types of treatment conditions will you need to set up and how will you do it? o How will you make sure that your data are of high quality (i.e., how will you reduce error)? FIGURE L6.1 Apparatus used to measure changes in gas pressure in response to changes in the volume of the gas. FIGURE L6.2 Apparatus use to measure changes in gas pressure in response to changes in the temperature of the gas. To determine how you will analyze the data, think about the following questions: o How will you determine if there is a difference between the treatment conditions and the control conditions? o What type of calculations will you need to make? o What type of graph could you create to help make sense of your data? Once you have finished collecting your data, your group will need to develop a mathematical model that describes how the pressure of a gas is affected by changes in the volume and temperature. When developing a mathematical model, variables that are inversely related are multiplied and variables that are directly related are divided. Keep these mathematical relationships in mind as you develop your model. The last step in this investigation is to test your model. To accomplish this goal, you can use your model to make predictions about the pressure of a gas in a closed system under different conditions. If you are able to make accurate predictions with your model, then you will be able to generate the evidence you need to convince others that your model is valid.
Connections to Crosscutting Concepts As you work through your investigation, be sure to think about the importance of developing causal explanations for observations, how models are used to help understand natural phenomena, the difference between laws and theories in science, and the difference between data and evidence in science. Initial Argument Once your group has finished collecting and analyzing your data, you will need to develop an initial argument. Your argument must include a claim, which is your answer to the guiding question. Your argument must also include evidence in support of your claim. The evidence is your analysis of the data and your interpretation of what the analysis means. Finally, you must include a justification of the evidence in your argument. You will therefore need to use a scientific concept or principle to explain why the evidence that you decided to use is relevant and important. You will create your initial argument on a whiteboard. Your whiteboard must include all the information shown in Figure L6.3. FIGURE L6.3 Argument presentation on a whiteboard Argumentation Session The argumentation session allows all of the groups to share their arguments. One member of each group stays at the lab station to share that group s argument, while the other members of the group go to the other lab stations one at a time to listen to and critique the arguments developed by their classmates. The goal of the argumentation session is not to convince others that your argument is the best one; rather, the goal is to identify errors or instances of faulty reasoning in the initial arguments so these mistakes can be fixed. You will therefore need to evaluate the content of the claim, the quality of the evidence used to support the claim, and the strength of the justification of the evidence included in each argument that you see. To critique an argument, you might need more information that what is included on the whiteboard. You might, therefore, need to ask the presenter one or more of the following questions, such as: What did your group do to analyze the data, and why did you decide to do it that way? Is that the only way to interpret the results of your group s analysis? How do you know that your interpretation of the analysis is appropriate? Why did your group decide to present your evidence in that manner? What other claims did your group discuss before deciding on that one? Why did you abandon those alternative ideas? How confident are you that your group s claim is valid? What could you do to increase your confidence? Once the argumentation session is complete, you will have a chance to meet with your group and revise your original argument. Your group might need to gather more data or design a way to test one or more alternative claims as part of this process. Remember, your goal at this stage of the investigation is to develop the most valid or acceptable answer to the research/guiding question! Report Once you have completed your research, you will need to prepare an investigation report that consists of three sections that provide answers to the following questions: 1. What question were you trying to answer and why? 2. What did you do during your investigation and why did you conduct your investigation in this way? 3. What is your argument? Your report should answer these questions in four pages or less. The report must be typed and any diagrams, figures, or tables should be embedded into the document. Be sure to write in a persuasive style; you are trying to convince others that your claim is acceptable and valid!
Investigation Timeline Option B Day 1 Stage 1: Identify the task and the guiding question. Hold a tool talk Small groups of students 50 Minutes Stage 2: Design a method Day 2 Groups then Finish Stage 2. Collect data 50 Minutes Groups then Stage 3: Analyze data and develop a tentative argument Day 3 Each group then shares its argument during an 50 Minutes Stage 4: Argumentation session If needed, groups can Collect additional data or reanalyze the collected data The teacher then leads an The teacher then leads an Stage 5: Explicit and reflective discussion Individual students then Homework Stage 6: Write and investigation report Day 4 The report then goes through a Stage 7: Double-blind group peer review 30 Minutes Homework Each student then Stage 8: Revises and submits his or her report
Investigation Proposal C The Guiding Question What data will you collect? How will you collect your data? How will you analyze your data? Your actual data I approve of this investigation. Instructor s Signature Date