Chemistry

1. Chemistry Gas Pressure

2. Crush the Can Demo: What Crushed the Can? • A pop can containing a small amount of water is heated until the water boils. • The can is then submerged in a pan of cold water • Crunch – the can is crushed

3. Crush the Can Demo: Energy Transfer Q Ek Ei Ech Ek Ei Ech Ek Ei Ech Water Water Water in Can Before Heating Water Boiling Water in Can in Cold Water Q Liquid Water Water Vapor (Gas) Liquid Water + Q = - Q =

4. Crush the Can Demo: Kinetic Theory of Matter Particles in the Can Water vapor condenses and collects at the bottom of can. No particles occupy the remaining space of the can Water vapor particles fill volume of can pushing air particles out Particles of liquid water are close, but free to flow. Gaseous air particle fill remaining volume of can

5. Crush the Can Demo:Air Pressure Gas particles in the air push down of the can. At first this “air” pressure is balanced by the “air” pressure inside the can. However, when the water vapor condenses, the “air” pressure inside the can is decreased dramatically.

6. Crush the Can Demo: Air Pressure Crushes the Can

7. Pressure (P) • The force of collisions on a certain area. • Pressure = Force Exerted / Area • Variety of units – psi, pascal, torr, mm of Hg, and atmospheres are some common examples. • Pressure can be measured by pressure gages / sensors, barometers, or manometers.

8. Atmospheric (Air) Pressure • Standard pressure at sea level is 760mm of Hg, or 101.3kPa. • Atmospheric pressure varies with weather conditions and altitude.

9. Measuring Pressure • Describe what happen to the water level in the manometer when the container’s pressure is less than atmospheric pressure. Label the area of high pressure and the area of low pressure.

10. Measuring Pressure • Describe what happened to the water level in the manometer when the container’s pressure is increased above atmospheric pressure.

11. Factors that Affect Gas Pressure • Temperature of the Gas • Volume of the Gas • Amount (mass) of the Gas • Altitude • Weather Conditions

12. Factors that Affect Gas Pressure: Altitude and Weather • Altitude and weather are two environmental conditions that would be difficult to test in the classroom. • To reduce the chance these factors might influence our results, we will conduct the investigation on the same day (same weather conditions) and at the same altitude.

13. Factors that Affect Gas Pressure: Mass (Amount of Gas) • Mass or the amount of gas present is also difficult to test in the lab. • During our investigation, the amount of gas (mass) will be kept constant by sealing the system to prevent any gas from escaping.

14. Factors that Affect Gas Pressure: Temperature • The affect of gas temperature on the pressure of a gas can be determined by using a pressure and temperature sensor • How does a change in temperature affect the pressure of a gas?

15. Factors that Affect Gas Pressure: Volume • The affect of gas volume on the pressure of the gas can be determined by using a syringe (marked in cc) and a pressure sensor. • How does a change in volume affect the pressure of a gas?

16. Pressure, Volume, and Temperature Lab • Make a two Vee diagrams for this lab • The first Vee diagram should focus on testing the affect of temperature on pressure • The second Vee diagram should focus on testing the affect of volume on pressure

17. Know Found Focus Question Background Value Claims I.V D.V C. Hypothesis Science Concepts Knowledge Claims Methods

18. Temperature (T) vs. Pressure (P) • Linear Relationship • Pressure is directly proportional to Temperature (constant Volume) • PT Pressure (kpa) Temperature (°C)

19. Volume (V) vs. Pressure (P) • Inverse Relationship • Pressure is Inversely proportional to Volume (constant Temperature) • P1/V Pressure (kpa) Volume (cc)

20. Why do gases behave this way? • Make a whiteboard to explain the results of the lab • Include diagrams of the gas particles and a description of the motion of the particles

21. Volume vs. Pressure Pressure (kpa) Volume (cc)

22. Volume vs. Pressure • Use the inverse relationship to fill in the missing volume and pressure measurements.

23. Volume vs. Pressure • Multiplying the volume by the corresponding pressure results in a constant. Etc…

24. Boyle’s Law • States the pressure of a gas is inversely proportional to the volume of the gas if temperature remains constant • Since both equations equal the same constant, you can set them equal to each other

25. Pressure vs. Temperature • What is the significance of the y-intercept? • To eliminate the y-intercept we must adjust our temperature scale so that zero temperature = zero pressure Pressure (kpa) Temperature (°C)

26. Pressure vs. Temperature • The Kelvin temperature scale sets zero temperature at zero pressure. • 0 K is called absolute zero • 0 °C = 273K Pressure (kpa) Temperature (K)

27. Pressure vs. Temperature Pressure (kpa) Temperature (K)

28. Pressure vs. Temperature • Use the linear relationship to fill in the missing temperature and pressure measurements.

29. Pressure vs. Temperature • Multiplying the initial temperature by the final pressure equals a constant

30. Pressure vs. Temperature • Since both equations equal the same constant, you can set them equal to each other • Volume remains constant

31. Volume vs. Temperature • Solve the first equation for P1 • Solve the second equation for P2

32. Charles's Law • Since the two pressures are equal, you can set the two equations equal to each other • Divide each side by pressure

33. Charles's Law • States the volume of a gas is directly proportional to the temperature of the gas if the pressure remains the same.