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Heat of Vaporization Lab

Heat of Vaporization Lab. We want to solve for H v : Fill in variables from data table; H v will be the unknown. Percent error:. To calculate percent error: Where accepted is 2.26x10 6 J/ kgC. Do Now (3/8/12):. What does the word “fluid” mean to you? List 5 examples of fluids

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Heat of Vaporization Lab

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  1. Heat of Vaporization Lab We want to solve for Hv: Fill in variables from data table; Hv will be the unknown

  2. Percent error: • To calculate percent error: • Where accepted is 2.26x106 J/kgC

  3. Do Now (3/8/12): • What does the word “fluid” mean to you? • List 5 examples of fluids • What does the word “pressure” mean to you?

  4. Do Now (5/31/12): • What principle describes the buoyant force? • What is a fluid? • What principle describes pressure in a fluid?

  5. Exam Review: • Please use the rest of class to work on your review packet. • Not working on your packet will result in a loss of 2 points for today!!! • If you have any questions or need any slides, please ask.

  6. Fluids and Pressure

  7. Fluids Fluid: materials that flow and have no definite shape of their own

  8. Pressure: the force on a surface F=force A=area Measured in Pascals (Pa)

  9. Brainstorm: • What animal do you think exerts the greatest pressure on the earth?

  10. A pig!!!

  11. Example #1: • A child weighing 364 N stands on the ground. His feet take up an area of 0.2 m2. What pressure does he exert on the ground?

  12. Example #2: • A child of mass 45 kg sits on a 5 kg 3 legged stool whose legs take up an area of 20 cm2. • What is the pressure exerted by the child and the stool? • If the child leans on two legs, what is the new pressure?

  13. Practice: • Use the rest of class to work on your homework: Density and Pascal’s Principle. It is due on Monday!

  14. Practice: • Use the rest of class to work on practice problems 1-2 on page 303 of your classroom textbook • If you finish, work on your lab • A-Course: Problems 1-5 on p. 344 of home textbook • B-Course: Problems 1,2,3,5 on p. 344 of home textbook – due Wed 3/16

  15. Review: Pressure • Strategies:

  16. Review: Density • Density: the amount of mass per unit volume • ρ=(rho) density • m=mass • V=volume

  17. Example: • The density of brass is 8.4 g/cm3. What is the approximate volume of a 800-g brass monkey?

  18. Do Now (3/9/12): HAPPY FRIDAY!!! A child exerts 4000 Pa of pressure on the ground. His feet take up an area of 0.2 m2. • What is his weight? • What is his mass?

  19. Atmospheric Pressure • The air pressure exerted on Earth at sea level; 1 atm = 105 Pa or 100 kPA

  20. Pascal’s Principle • Any change in pressure applied at any point on a confined fluid is transmitted undiminished throughout the entire fluid • Think of squeezing toothpaste out of a tube!

  21. Hydraulic Lift a hydraulic apparatus used to lift or move objects using the force created when pressure is exerted on liquid in a piston

  22. Hydraulic Lift • Pascal’s Principle: • Force exerted by a hydraulic lift:

  23. Example: • In a machine shop, a hydraulic lift is used to raise heavy equipment for repairs. The system has a small piston with a cross sectional area of 0.01 m2 and a large piston with cross sectional area of 0.20 m2. How much load can be lifted by the large piston if 150 N of force is exerted into the small piston?

  24. Practice: • Please use the rest of class to finish your homework. • If you finish your homework, please meet with your mousetrap car group!! • Mousetrap cars need to be built by MONDAY MARCH 19

  25. Do Now (3/12/12): • The input piston of a hydraulic lift is 0.2 m in diameter, and the output piston is 0.1 m in diameter. How much output force will an input force of 4 N produce?

  26. Linear Expansion • Absorption of heat causes an increase in length; release of heat causes a decrease

  27. Linear Expansion • L= length • ΔL=change in length • ΔT= change in temperature • αL= coefficient of linear expansion

  28. Coefficient of Linear Expansion • The degree of expansion divided by the change in temperature for each material

  29. Example: • A copper pipe is 100 meters long at 5oC. The pipe is heated to 105oC. The coefficient of linear expansion for copper is 2.0 x 10-5 / oC. What is the change in length of the copper pipe? 

  30. Pre-Lab • You have the rest of class to work on your pre-labs. They are due at the end of class!!! • Once you finish, get together with your group and work on your mousetrap car. It is due NEXT Monday, 3/19!!!

  31. Accepted Linear Expansion Values of Common Materials Material a(x10-5 °C-1) Glass (ordinary) 0.09 Glass (Pyrex) 0.32 Concrete 1.20 Steel 1.24 Copper 1.76 Aluminum 2.34 Lead 2.90

  32. Do Now (3/13/12): • What is a Bunsen burner? • How does it work? • What are some good safety guidelines to keep in mind when working with Bunsen burners?

  33. Do Now: The Forth railway bridge has an overall length of 2,529 m (about 1½ miles). It is made of steel (coefficient of linear expansion = 0.000012 per °C). If the greatest difference in temperature between the coldest and hottest days is 35°C what is greatest the length the bridge can change by?

  34. Do Now: • What is the pressure on the ground of a 4 kg brick whose bottom is 0.3 m long and 0.2 m wide? • Turn in homework and Do Now’s

  35. Mousetrap cars • Should be completely DESIGNED by Monday!!! If you have already built yours, then you are ahead of the game 

  36. Archimedes Boat • Get together with a group of 3-4 people to design a boat based on the specifications on your paper. Your drawing should include specific designs and measurements!!! When you are finished, check in with me.

  37. Do Now (3/15/12): Take out your boat design. Discuss your reasoning with your neighbor and list two reasons for your boat’s shape.

  38. Do Now: • What is Archimedes Principle? • How did it relate to yesterday’s lab?

  39. Do Now (3/16/12): • How well did your boat do yesterday? What design decisions do you think caused your success or lack thereof?

  40. Archimedes’ Principle • An object immersed in a fluid has an upward force on it equal to the weight of the fluid displaced by the object • ρfluid=density of the fluid • V=volume of object • g=9.8

  41. Example • A cubic decimeter (1x10-3m3) of a granite building block is submerged in water. The density of granite is 2.7x103kg/m3. the density of water is 1000 kg/m^3 • What is the buoyant force acting on the block?

  42. Buoyant Force • Less dense materials FLOAT when mixed with more dense materials • More dense materials SINK when mixed with less dense materials

  43. Units • Density: kg/m3 • Mass: kg • Volume: m3 • If your units are not in these, you must convert!!!

  44. Practice: • Use the rest of class to work on the paper Archimedes Principle. It will be due next week!!! • You will also have a test next week!!!

  45. Do Now (3/19/12): • Think back to our unit on energy. What type of energy do you think a mousetrap has before it is sprung? • What is the area of the trapezoid?

  46. Mousetrap Lab: • The area under the curve of a Force-distance graph is the potential energy!

  47. Mousetrap Lab: • Pass in final car designs and Boat Labs, then head over to room 127.

  48. Do Now (3/20/12): • What is the buoyant force exerted on a steel object with volume 2x10-3 m3 floating in crude oil? The density of crude oil is 900 kg/m3 and the density of steel is 7850 kg/m3.

  49. Practice Problem: A gold crown (density is 19,300 kg/m3) weighs 40 N in air. • What is the volume of the crown? • What is the buoyant force of the crown? • What will it weigh when suspended in crude oil whose density is 900 kg/m3?

  50. Practice: • Use the rest of class to work on the paper Archimedes Principle. It is due tomorrow!!! • Mousetrap labs are due Friday!!! Come in tomorrow with any questions about the lab!!!

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