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PhysicsPhysics lesson lesson

9 9 classclass

EVAPORATION AND BOILINGEVAPORATION AND BOILING

Compare the processes on these Compare the processes on these points:points:

Start and final state of the mattersStart and final state of the matters Conditions necessaryConditions necessary for the processfor the process Temperature changesTemperature changes Internal energyInternal energy

SPIRITS EVAPORATIONSPIRITS EVAPORATION

Watch the changing of Watch the changing of the temperature during the temperature during spirits evaporation spirits evaporation

Make an inferenceMake an inference

BOILING OF WATERBOILING OF WATER

How does the How does the temperature change temperature change during the heating of during the heating of the water?the water?

Watch the changes in Watch the changes in the liquid the liquid

1. 1. EVAPORATIONEVAPORATION EVAPORATION-the process of molecule EVAPORATION-the process of molecule

separation from the free liquid surfaceseparation from the free liquid surface Liquid is changing into vapourLiquid is changing into vapour During evaporation the fastest molecules leave the During evaporation the fastest molecules leave the

free surface and the molecules ,that remain in the free surface and the molecules ,that remain in the liquid ,have smaller kinetic energy. This is way the liquid ,have smaller kinetic energy. This is way the liquid cools down.liquid cools down.

2. BOILING2. BOILING

Boiling-the process vaporization from the whole volume of Boiling-the process vaporization from the whole volume of the liquidthe liquid

At constant pressure, while the liquid is boiling, despite the At constant pressure, while the liquid is boiling, despite the heat supply, the temperature remains constant /heat supply, the temperature remains constant /boiling boiling pointpoint//

The boiling point is a quantity characteristic of the deferent The boiling point is a quantity characteristic of the deferent liquidsliquids

The boiling point of a liquid depends on external pressure-The boiling point of a liquid depends on external pressure-when the pressure is higher, the boiling point riseswhen the pressure is higher, the boiling point rises

Latent heat of vaporization/Latent heat of vaporization/rr/-the quantity of heat, needed /-the quantity of heat, needed for a unit mass of a given liquid to be turned into vapor at for a unit mass of a given liquid to be turned into vapor at constant temperatureconstant temperature

r=Q/m r=Q/m

3. CONDENSATION 3. CONDENSATION

Condensation-process Condensation-process of changing vapour of changing vapour into liquidinto liquid

ON-LINE PHYSICS LAB ON-LINE PHYSICS LAB INDIVIDUAL ACTIVITIES INDIVIDUAL ACTIVITIES INDIVIDUAL ACTIVITIES INDIVIDUAL ACTIVITIES

IN INTERACTIVE EXPERIMENTSIN INTERACTIVE EXPERIMENTS

Fit together the Fit together the necessary equipment necessary equipment and examine the and examine the process under process under following conditions:following conditions:– Constant temperatureConstant temperature– Heating Heating – Cooling Cooling

4. PUTTING EVAPORATION AND 4. PUTTING EVAPORATION AND BOILING INTO PRACTICE BOILING INTO PRACTICE

Distillation Distillation Separating compositesSeparating composites Autoclaves Autoclaves Vacuum apparatuses Vacuum apparatuses

EXAMINE YOURSELF EXAMINE YOURSELF

1. 1. You have to watch evaporation at: You have to watch evaporation at:

А) Low temperature

B) High temperature

C) Any temperature

Mistake!Mistake!

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Mistake!Mistake!

NextPrevious question

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Mistake!Mistake!

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CorrectCorrect!!

Previous question

Examine yourselfExamine yourself

2.2.What is the correlation between waters What is the correlation between waters boiling point in open container at see boiling point in open container at see level /Tlevel /T11/ and on the mountain top/T/ and on the mountain top/T22/? /?

А) Т1 = Т2

B) Т1 > Т2

C) Т1 < Т2

Examine yourselfExamine yourself

3. 3. What amount of heat is required for the What amount of heat is required for the complete evaporation of 200 g water at complete evaporation of 200 g water at temp.100 temp.100 °°CC? ( r = 2260 kJ/kg)? ( r = 2260 kJ/kg)

А) 4,52.105 J

B)2,26.105 J

C) 4,52.107 J

THANK YOU FOR YOUR THANK YOU FOR YOUR ATTENTION!ATTENTION!