5.18

5.17 Demo

02 November 2011

19:56

Cloud formation

·         Place a little water in the bottom of a 1½ litre plastic bottle

·         Squeeze a few times

·         Introduce a small amount of smoke

·         Squeeze and release several times

·         When you squeeze, the cloud disappears; when you release, the cloud reforms

 

 

Explanation

·         When the pressure increases the temperature increases and vica versa

·         The smoke particles are nucleating sites on which the water can condense

 

 

 

5.18 Gay-lussac's law

28 October 2011

11:11

·         5.18 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume:

                p₁ / T₁ = p₂ / T₂

p₁ = Pressure at the beginning [kPa, bar or atm ]

T₁ = Absolute temperature at the beginning [K]

p₂ = Pressure at the end [kPa, bar or atm]

T₂ = Absolute temperature at the end [K]

(Note: the units of temperature must be Kelvin, not ^oC!  The units of pressure can be any, as long as the same at the beginning and the end)

 

 

5.18 Ideal graph and conclusion

09 November 2011

15:15

 

 

5.18 Question

07 November 2011

15:08

Collins, p.116

a.If we cool the gas in a rigid, sealed tin can, what happens to the pressure inside the can? (1 mark)

P1/T1 = P2/T2  

20+273= 293=    55+273=328

3/293 = P2/328

P2= (3 x 328) / 293 = 3.36 Bar

b.               Explain your answer to part a. by using the Kinetic Theory (4 marks)

When the temperature decrease, the kinetic energy decrease making the particles moving slower and colliding less, hitting the walls less frequently  therefore have less pressure.