Properties of Gases and Laws with Computations and Examples

Simplified learning material about Properties of Gases ang Laws for easy understanding.

1. PROPERTIES OF GASES

2. PROPERTIES OF GASES Temperature (T) Pressure (p) Volume (V) Gases are affected by 3 variables Gases have no definite volume Gases are highly compressible Gases are lighter than liquids

3. ATMOSPHERIC PRESSURE Air has weight = 1.225 kilograms per cubic meter or 0.0001225 grams per cubic centimeter (cc) Air is like a fluid that is several miles deep Pressure is Force per Area At sea level, on a standard day, - Air Pressure = 14.7 lb /in2 <- (squared) - Air Pressure = 101.32 kPa

4. ATMOSPHERIC PRESSURE Straw - Air Pressure in the straw is less than the outside air pressure - Outside air pressure forces fluid up the straw

5. AIR PRESSURE Air Pressure decreases as altitude increases - Mountain Climbing - Pressurized airplanes Because there is an amount of oxygen required above certain altitudes.

6. AIR PRESSURE Photo not mine. Credits to the rightful owner.

7. PROPERTIES OF GASES Gauge Pressure: Pressure on a gauge does not account for atmospheric pressure on all sides of the system. Absolute Pressure: Atmospheric pressure plus gauge pressure Absolute Pressure Take note: Gauge Pressure + Atmospheric Pressure = Absolute Pressure

8. PROPERTIES OF GASES Pressure (p) is measured in pounds per square inch ( lb /in.2 or psi) Standard atmospheric pressure equals 14.7 lb /in.2 Absolute Pressure If a gauge reads 120.0 psi, what is the absolute pressure?

9. PROPERTIES OF GASES Absolute Pressure If a gauge reads 120.0 psi, what is the absolute pressure? 120.0 lb /in.2 + 14.7 lb /in.2 = 137.7 lb /in.2

10. PROPERTIES OF GASES Absolute Temperature Absolute Zero = -460 F or -273 C Absolute Temperature is measured in degrees Rankine (R) or Kelvin (K) R = F + 460 K = C + 273 Standard Temperature is 273 K or 492 R If the temperature of the air in a system is 65 F, what is the absolute temperature?

11. PROPERTIES OF GASES Absolute Temperature If the temperature of the air in a system is 65 F, what is the absolute temperature? Answer: 65 F + 460 = 525 R

12. PROPERTIES OF GASES Converting Celsius to Fahrenheit Formula: Tf = (9/5 x Tc) + 32 Converting Fahrenheit to Celsius Formula: Tc = (5/9 x Tf ) - 32

13. PASCAL’S LAW Pressure exerted by confined fluid acts undiminished equally in all directions. Pressure: The force per unit area exerted by a fluid against a surface Formula: p = F/A Photo not mine. Credits to the rightful owner.

14. PASCAL’S LAW How much pressure can be produce with a 3 in. diameter (d) cylinder and 50 lb of force? Formula: A=πr2 <- (squared) A=π(1.5(2)) <- (squared) A=7.1 in.2 <-(squared) p = F/A p = 50 lb/7.1 in.2 p = 7.0 lb/ in.2 Photo not mine. Credits to the rightful owner.

15. PERFECT GAS LAWS The perfect gas laws describe the behavior of pneumatic systems Boyle’s Law Charles’ Law Gay-Lussac’s Law

16. BOYLE’S LAWS The volume of a gas at constant temperature varies inversely with the pressure exerted on it. Formula: p1 (V1) = p2 (V2)

17. BOYLE’S LAWS A cylinder is filled with 40. in.3 of air at a pressure of 60. psi. The cylinder is compressed to 10.in.3. What is the resulting absolute pressure? p1 = 60. lb /in.2 p2= ? V1 = 40. in.3 V2= 10. in.3 Convert p1 to absolute pressure. p1 = 60. lb /in.2 + 14.7 lb /in.2 = 74.7 ln.2

18. BOYLE’S LAWS Formula: p1(V1) = p2(V2) 74.7 lb /in.2 (40.in.3) = p2(10.in.3) 29 88 in.- lb 10 in.3 2 = p2 = p2 298.8 lb / in2 or 300 lb / in2

19. CHARLES’ LAWS Volume of gas increases or decreases as the temperature increases or decreases, provided the amount of gas and pressure remain constant. Formula: V1/T1 = V2/T2 Note: T1 and T2 refer to absolute temperature

20. CHARLES’ LAWS An expandable container is filled with 28 in.3 of air and is sitting in ice water that is 32 F. The container is removed from the icy water and is heated to 200 F. What is the resulting volume? V1 = 28 in.3 V2 = ? T1 = 32 F T2 = 200 F Convert T to absolute temperature T1 = 32 F + 460 F = 492 R T2 = 200 F + 460 F = 660 R

21. CHARLES’ LAWS An expandable container is filled with 28 in.3 of air and is sitting in ice water that is 32 F. The container is removed from the icy water and is heated to 200 F. What is the resulting volume? Formula: V1/T1 = V2/T2 28 in.3 = V2 492 R = 660 R 18480 in3 R 492 R = V2 37.56 in.3 = V2 Final Answer: V2= 37.56 in3 or 38 in3

22. GAY-LUSSAC’S LAWS Absolute pressure of a gas increases or decreases as the temperature increases or decreases, provided the amount of gas and the volume remain constant. Formula: p1/ T1 = p2/ T2 Note: T1 and T2 refer to absolute temperature Note: p1 and p2 refer to absolute pressure

23. GAY-LUSSAC’S LAWS A 300. in.3 sealed air tank is sitting outside. In the morning the temperature inside the tank is 62 F, and the pressure gauge reads 120. lb /in.2. By afternoon the temperature inside the tank is expected to be close to 90. F. What will the absolute pressure be at that point? V = 300. in.3 p1 = 120. lb /in.2 p2 = ? T1 = 62 F T2 = 90 F

24. GAY-LUSSAC’S LAWS V = 300. in.3 p1 = 120. lb /in.2 p2 = ? T1 = 62 F T2 = 90 F Convert p to absolute pressure. p1 = 120. lb /in.2 + 14.7 lb /in.2 = 134.7 lb /in.2 Convert p to absolute temperature. T1 = 62 F + 460 F = 522 R T2 = 90 F + 460 F = 550 R

25. GAY-LUSSAC’S LAWS 134.7 lb /in.2 = p2 522 R 550 R 74085 lb /in.2 R = p2 522 R p2 = 140 lb / in. 2 If the absolute pressure is 141.9 lb /in.2, what is the pressure reading at the gauge? 14 1.9 lb /in.2 - 14.7 lb /in.2 = 12 7.2 lb /in.2 = 130 lb / in. 2

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