Act_7 - Name Section Activity Sheet 7 Applications of the...

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1/23/05 1 Name: ___________________________________ Section: ______________ Activity Sheet 7: Applications of the Laws of Thermodynamics 7.1 Conservation of Energy Your instructor will discuss how changes in internal energy U relate to energy conservation. 1) Internal Energy Your instructor will demonstrate two rolling carts colliding with a barrier. Both carts have the same mass and the same frictional force with the table top. a) Which cart has more kinetic energy after it hits the barrier – the cart that rolls back a shorter distance or a longer distance? ________________________ How do you know? b) Now watch the carts, without their outer covers, collide with the barrier. How can you explain the difference in the kinetic energy of the carts after they hit the barrier? c) Explain how energy was conserved when each cart collided with the barrier. d) How does this demonstration illustrate an increase in the internal energy of an object? 7.2 Pressure, Temperature, Volume and the Ideal Gas Law 2) Crushing Cans Your instructor will illustrate the relationship between pressure and volume by changing the internal energy and the phase of water molecules inside cans. a) What happens to the internal energy and the motion of the water molecules in the can as the water is heated into steam? b) Pressure in the can is caused by the collisions of molecules of steam with the can walls. When the water is heated, what happens to the pressure inside the can?

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1/23/05 2 c) What happens to the motion of the water molecules and the pressure inside the can when the steam is quickly cooled and condenses into liquid water? d) Why do the walls of the can collapse? 3) The Ideal Gas Law Next we consider the relationship among pressure, temperature, volume, and number of molecules of a gas and discuss the Ideal Gas Law. We will find that ratio reasoning is useful and can be based on proportionalities. a) The previous demonstration discussed the relationship between the temperature of a gas and the pressure the gas exerts on the walls of a container. At a fixed volume of gas, pressure and temperature are directly proportional. Write a proportionality to show this relationship. __________________ Write a ratio of the initial pressure of a gas P initial (or P i ) to the final pressure P final (or P f ) and a second ratio of the initial gas temperature T i to the final temperature T f . Based on your proportionality above, relate these two ratios by an equation. b)
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Act_7 - Name Section Activity Sheet 7 Applications of the...

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