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Unit 2 Changes in Matter

Unit 2 Changes in Matter. Section 1 Solid, Liquid, Gases Page 30 to 32 of binder Pull pages 32 to 37. Defined. Undefined. Undefined. Defined. Defined. Undefined. How does kinetic energy change from state to state?. Unit 2 Changes in Matter. Section 2 Behavior of Gases Pages 32 to 37.

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Unit 2 Changes in Matter

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  1. Unit 2 Changes in Matter Section 1Solid, Liquid, Gases Page 30 to 32 of binder Pull pages 32 to 37

  2. Defined Undefined Undefined Defined Defined Undefined How does kinetic energy change from state to state?

  3. Unit 2 Changes in Matter Section 2Behavior of Gases Pages 32 to 37

  4. Gas is everywhere Question What are the three properties of a gas that can be measured? Temperature, Pressure and Volume

  5. Under Pressure Gases are mostly empty space with molecules of the gas traveling in a fast random motion (high Kinetic Energy). These molecules collide with each other and any other matter in their path. It is the collision of these gas molecules that exert a force and allow us to feel pressure.

  6. What is Pressure? Pressure is defined as the measure of a force that is applied to a given area. The force the atmosphere exerts on an object at sea level is equal to 1 atmosphere and is equal to 14.7 pounds of force per square inch.

  7. Boyle’s Law At a constant temperature, the volume of a gas varies inversely with the pressure. BoylePlays Volleyball Question What does inversely mean? Inversely means to respond in an opposite way. If one variable goes up, the other variable goes down.

  8. By keeping the temperature constant in his experiments, Boyle found that when he doubled the pressure, the volume decreased by one-half. When he tripled the pressure, the volume decreased to one-third of its original value. Pressure * Volume = a constant value Demonstration 1 1/2 2 3

  9. For a gas at a constant temperature, what is the relationship between volume and pressure? If volume increases, pressure ___________. If volume decreases, pressure __________. This is a (n) _________________ relationship. This relationship produces a ________ sloped line.

  10. The Mathematical Application of Boyle's Law Chlorine gas has a volume of 5.00 liters at a pressure of 3.20 atmospheres. (3.20 times normal) Without changing the amount of gas or temperature (these values are constant), what would the pressure be if we decreased the volume to 1.50 liters? Using Boyle’s Law, if volume decreases, pressure should __________________.

  11. Step 1- Formula Since the product of the volume times the pressure for the initial conditions (represented as V before and P before) has to be equal to the product of the volume times pressure for the final conditions (represented as V after and P after), the equation is written as: Before = After Volume before * Pressure before = Volume after * Pressure after

  12. Step 2- Plug info into formula Plug in the numbers that are known. The initial volume is 5.0 liters The initial pressure is 3.20 atmospheres. The final volume is 1.5 liters. The final pressure is unknown Volume before * Pressure before = Volume after * Pressure after (5.00 L) * (3.20 atmospheres) = (1.50 L) * Pressure after (5.00 L)(3.20 atmospheres) = Pressure after (1.50 L) 10.67 atmospheres = Pressure after

  13. If we plot the volume of a gas vs. the pressure of a gas at a constant temperature, what type of slope would be produced?

  14. Real Life Application of Boyle’s Law Perhaps the most obvious consequence of Boyle's Law is the way a passenger's ears "pop" when taking off in an airplane. The fixed volume of air inside the ear canal expands as air pressure in the plane's cabin decreases on takeoff, causing the sensation of pressure inside the ear. At higher altitudes, the cabin is "pressurized," so that pressure within and out of the ear are equal. Dignitaries had gathered to celebrate the completion of a tunnel under the Thames River by drinking a little bubbly on location. No matter that the champagne seemed lifeless and flat: They drank their fill anyway. But upon their return aboveground to reduced atmospheric pressure, the drink began to release its gas-- fast. "The wine popped in their stomachs, distended their vests, and all but frothed from their ears," said the "Journal of Chemical Education." "One dignitary had to be rushed back into the depths to undergo champagne recompression." When World War II pilots began complaining of severe bouts of intestinal gas, it became clear that a few beans eaten on the ground can feel like a lot more in the relative depressurized environment of high-altitude flight

  15. Discussion Questions for Boyle’s Law 1. What happens to the pressure of a given quantity of gas if the gas’s volume is decreased without changing its temperature? Why? 2. Is the oxygen used by scuba divers stored at high pressure or low pressure? Why? As the volume of a gas decreases, the pressure of the volume increases if temperature remains constant. High Pressure- the tank is a small volume of air stored at high pressure

  16. Discussion Questions for Boyle’s Law 3. What does it mean to say that the pressure of a gas varies inversely with volume? 4. If an 8-L container of nitrogen is at a pressure of 1 atmosphere, how much must the volume of this gas be increased to obtain a pressure of 0.5 atmosphere? As pressure decreases, volume increase Volume before * Pressure before = Volume after * Pressure after 8 Liters * 1 atm = Volume after * .5 atm 8/ .5 = Volume after 16 Liters = Volume after

  17. Discussion Questions for Boyle’s Law 5. To exhale does a person need to reduce or expand the volume inside his or her chest cavity? In answering this question, discuss the relationship between the volume and the pressure of a gas. 6. Is the pressure of the carbon dioxide inside a soda bottle greater or less than the pressure of the surrounding air? Explain. As you inhale, you increase the volume of your lungs which reduces the pressure Pressure inside a soda bottle is greater than the pressure of the atmosphere- evidence- soda fizzes when you open it because the volume of the soda increases releasing pressure.

  18. Discussion Questions for Boyle’s Law 7. Which makes better soda bottles — glass or plastic? Why? Plastics better withstand the changes in pressure and volume of the soda.

  19. Charles’ Law Jacques Alexander Charles studied the effect of temperature on the volume of a gas in the late 1780s When a sample of gas is held at a constant pressure, the volume is directly proportional to the temperature on the Kelvin scale. Question: What does directly proportional mean? Directly proportional means to respond in same way. If one variable goes up, the other variable goes up.

  20. When the pressure of the gas is constant, if the temperature of a gas is increased, the volume of that gas must also increase. Conversely, if the temperature is decreased, the volume of that gas has to decrease. Volume = constant Temperature Demonstration 1 2 3 1/2 1/3

  21. With the pressure of the gas held constant: As the temperature of a gas is increased, the volume of that gas must ________________. As the temperature is decreased, the volume of that gas must ________________. This is a _________________ relationship. This relationship produces a ________ sloped line.

  22. Mathematic Application of Charles’ Law For a sample of gas at a specific pressure with a volume of 3.50 L at 298 K (Kelvin = 273 + Celsius), it is possible to calculate the volume of that gas if the temperature were raised to 450 K.

  23. Step 1- Formula Since the product of the volume divided by temperature for the initial conditions (represented as V before and T before) has to be equal to the product of the volume divided by temperature for the final conditions (represented as V after and T after), the equation is written as: Before = After Volumebefore = Volume after Temperature before Temperature after

  24. Step 2- Plug info into formula Plug in the numbers that are known. The initial volume is The initial temperature is 450 Kelvin. The final volume is 3.5 liters The final temperature is 298 Kelvin Volume before = Volume after Temperature before Temperature after

  25. If we plot the volume of a gas vs. the temperature of a gas at a constant pressure, what type of slope would be produced?

  26. Discussion Questions for Charles’ Law 1. What happens to a balloon filled with air if it is put in a freezer? Why? 2. When the temperature of a gas is doubled, and the amount and the pressure of the gas are kept constant, what happens to the volume? 3. If 2 L of oxygen at 20°C are heated to 60°C, what will be the new volume? Assume that the amount of gas and the pressure remain constant. 2 Liters = Volume after (20 +273) (60 + 273) 2 Liter * (60 + 273 K) = Volume after (20 +273 K) 2.3 Liters = Volume after 4. If a balloon filled with gas is heated, what happens to the balloon? Why?

  27. Gas SummaryPressure, Temperature and Volume Indirect Negative K= P*V Boyle Exponential Direct Linear K= T/P Bryce positive K= V/T Direct positive Charles Linear

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