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Ch3.2 and 3.3

Ch3.2 and 3.3. Fluids. What do liquids and gases have in common? States of matter Do not have a fixed shape Ability to flow, particles can move past each other easily. Buoyant Force. Why doesn’t a rubber duck sink to the bottom of a bath tub?

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Ch3.2 and 3.3

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  1. Ch3.2 and 3.3

  2. Fluids • What do liquids and gases have in common? States of matter Do not have a fixed shape Ability to flow, particles can move past each other easily

  3. Buoyant Force • Why doesn’t a rubber duck sink to the bottom of a bath tub? • A force pushes the rubber duck to the top of the water.

  4. Buoyant Force • This force is an upward force that fluids exert on matter. • What keeps the ice floating?

  5. Ice cube floating in water • The pressure exerted on the right is equal to the pressure exerted on the left. Theses forces cancel out.

  6. Ice cube floating in water Pressure increases as depth increases. Pressure increases Net force is upward (buoyant force)

  7. Archimedes’ principle • The buoyant force on an object is an upward force equal to the weight of the fluid that the object displaces.

  8. Change the shape of an object and you can change the density.

  9. A solid brick’s density is 1.9g/cm3. And the density of water is 1.00g/cm3 . How could you get the brick to float?

  10. Where have you heard the word “pressure” in conversation? • Air pressure • Water pressure • Tire pressure • Blood pressure

  11. Pressure • When you pump up a bike tire, what is going on inside the tire?

  12. Pressure

  13. Pressure • Pressure is calculated by using the equation below. pressure = Force area Pressure unit is pascal (Pa). It is equal to 1N/m2

  14. Pascal’s Principle • When you blow a bubble, you blow air in one direction. So why does the bubble get rounder as you blow, instead on longer? Fluid property: Fluids exert pressure evenly in all directions.

  15. Pascal’s Principle • P1 = P2 • So our equation can now look like this: F1 = F2 A1 A2

  16. Pascal’s Principle

  17. What do you observe?

  18. Fluids in motion • Give an example of a moving fluid. air moving as wind water moving through pipes food coloring moving through water

  19. Fluids in motion • Fluids move faster through smaller areas than through larger areas

  20. Viscosity • How are honey and lemonade similar? How are they different? • Viscosity is a liquid’s resistance to flow. It is the attraction between the particles that make it viscous.

  21. Examples • Think of 5 every day items that are viscous. Can you find a way to change their viscosity? Temperature

  22. Ideal Gas • P1V1= P2V2 T1 T2 The three laws we will look at take a variable out of this equation and hold it constant.

  23. Ideal Gas • Boyle’s Law P1V1= P2V2 Temperature stays constant, so we remove it from the combined gas equation. This was the marshmallow experiment.

  24. Ideal Gas • Boyle’s Law – Pressure increases, volume decreases. They are inversely proportional.

  25. Ideal Gas • Charles’ Law V1 = V2 T1 T2 Pressure stays constant Frozen balloon Room temp balloon

  26. Ideal Gas • Charles’ Law

  27. Ideal Gas • Gay-Lussac’s Law • P1= P2 T1 T2 Directly proportional

  28. Ideal Gas

  29. Practice Problems • Charles’ Law If I have 45L of helium in a balloon at 298K and increase the temperature of the balloon to 328K, what will the new volume of the balloon be?

  30. Practice Problem • Charles Law I have 130L of gas in a piston at a temperature of 523K. If I cool the gas until the volume decreases to 85L, what will the temperature of the gas be?

  31. Practice Problem • Gay-Lussac’s Law 10.0 L of a gas is found to exert 97.0 kPa at 298K. What would be the required temperature to change the pressure to 101.325kPa?

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