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Rate of evaporation of different liquids

 

Evaporation Rate of Different Liquids: We know that all liquids can evaporate at room temperature and normal air pressure. Evaporation means the process of transformation in liquid from its liquid state to gaseous phase. Evaporation is not the same as boiling point.

A Liquid and its molecules in a liquid state gain sufficient energy to penetrate the gaseous state.

The thermal motion of a particle must be enough to overcome the surface tension of the liquid for it to evaporate, that is, its kinetic energy must exceed the work function of cohesion at the surface.

Evaporation occurs more instantly at a higher temperature and in liquids with lower surface tension. Since just a small proportion of the molecules are situated close to the surface and are moving the correct way to escape at any given moment, the rate of evaporation is limited. Quick moving molecules will survive, and remaining particles got bring down average kinetic energy, it might raise temperature decrease.

If the Evaporation process takes place in a closed vessel, the escaping electrons accumulate as a vapour above the liquid. Many of the particles return to the liquid, with returning fragments becoming more frequent as the density and pressure of the vapour increases. At the point when the procedure of escape and return achieves balance, the vapor is said to be “saturated,” and no further change in either vapor pressure and density or liquid temperature will occur.

 

Factors Influencing Rate Of Evaporation:-

Concentration of other substances in the air-
The strength of the content is evaporating in the air. If the wind already has a high level of the material fading, then the given substance will disappear more slowly.

The concentration of other substances in the air. If the wind is already saturated with other elements, it can have a lower capacity for the material evaporates.

The temperature of the substance – If the material is hotter, then evaporation will be faster.

The flow rate of air-This is in part related to the concentration points above. If fresh air is moving over the substance all the time, then the concentration of the material in the atmosphere is less likely to go up with time, thus encouraging faster evaporation. When the molecules are in motion, get more energy than out of rest. Due to which when the flow of air is stronger, the higher the evaporating power of the air molecules.

Inter-molecular forces-If there is an Inter molecular force in Liquid may raise stronger troops retaining the molecules together in the liquid or solid state the more energy that must be input to evaporate them.

 

The rate of evaporation may also depend on Vapour Pressure.
Vapour pressure is the pressure used by vapours in equilibrium with its liquid at a delivered temperature in a closed system.

Different liquids have a different vapour pressure. A substance with high vapour pressure is a more volatile while with less vapour pressure is less volatile.

A substance having a more significant force of attraction between molecules are less volatile due to strong bonding in between the particles and therefore have a low vapour pressure.

So all it depends on vapour pressure and force of attraction.

 

Why do different liquids have a different rate of evaporation?

Evaporation means Conversion from liquid to gaseous state
-which means distance from one molecules to another increases
-which means it depends on inter molecular force of attraction in liquid.
it means they have different type(distance and type of attraction etc.) of inter molecular force of attraction.
Different types of force require different amount of energy or at same energy they will have a different rate of evaporation.

Experiment – 1

The rate of evaporation of water, Diethyl Ether, acetone by comparing them.

Item Required for Experiment:- Pipette, Beaker, China dish, Weighing balance Measuring flask, Acetone, Distilled water, Diethyl ether, Watch glass.

PROCEDURE:

1. Take three china dishes.
2. Pipette out 10 ml of each sample.
3. Dish A-Acetone
Dish B-Water
Dish C-Diethyl ether
4. Record the weights before beginning the experiment.
5. Leave the three dishes undisturbed for ½ an hour and wait patiently.
6. Record the masses of the samples after the given time.
7. Compare the prior and present observations.

Observation Table

Water (gms)
Acetone (gms)
Diethyl Ether (gms)
Weight of dish
50
50
50
Weight of (dish + substance) before evaporation
60
57.85
57
Weight of (dish + substance) after evaporation
59.8
55.55
54.33
Weight of substance evaporated
0.2
2.3
2.67

Inference And Conclusion: –
The rate of evaporation of the given three liquids is in order:-
Diethyl Ether>Acetone>Water
Reason: –
Water has extensive hydrogen bonding in between oxygen atom of one molecule and hydrogen atom of another molecule. But this is absent in the case of acetone.

Experiment – 2

The surface area affected by the rate of evaporation of Diethyl ether.

Observation Table

Petridish Mark
Diameter of petridish
Time taken for complete evaporation
A
2.5 cm
11min 45sec
B
5.0 cm
8min 45sec
C
7.5 cm
6min 30sec

 

Requirement
10 ml pipette and stopwatch, three Petri dishes of diameter 2.5 cm,5 cm, and 10 cm with covers,

Procedure
1. Clean and dry the Petri dishes and mark them as A, B, C.
2. Pipette out 10 ml of Diethyl ether in each of the Petri dishes a, band C covers them immediately.
3. Uncover all the three Petri dishes simultaneously
And start the stopwatch.
4. Note the time when diethyl ether evaporates entirely from each Petri dish.

Result
It observed that maximum evaporation occurs in Petri dish with the most massive diameter followed by smaller
And the smallest Petri dish. It is, therefore, concluded that rate of evaporation increases with increase in surface area.

 

CONCLUSION

In this experiment, the evaporation trends were more consistent with all liquids and they seemed to make a big jump from day 2 to 3.

The jump in evaporation levels from day 2 to day 3 in the heated experiment is due to the liquids becoming warmer causing the molecules to move around faster which helps the liquids turn into a vapor quicker. The consistencies of the evaporation levels in the first experiment (natural) were most likely due to the liquids’ densities.

The water was evaporating faster at the higher temperature.

 

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