Suggest an experiment to prove that the rate of evaporation of a liquid depends on its surface area and the vapor already present in the surrounding air.
Answer (2)
That's two different things it depends on:
-- surface area exposed to the air AND -- vapor already present in the surrounding air.
Here's what I have in mind for an experiment to show those two dependencies:
-- a closed box with a wall down the middle, separating it into two closed sections;
-- a little round hole in the east outer wall, another one in the west outer wall, and another one in the wall between the sections; So that if you wanted to, you could carefully stick a soda straw straight into one side, through one section, through the wall, through the other section, and out the other wall.
-- a tiny fan that blows air through a tube into the hole in one outer wall.
Experiment A:
-- Pour 1 ounce of water into a narrow dish, with a small surface area. -- Set the dish in the second section of the box ... the one the air passes through just before it leaves the box. -- Start the fan. -- Count the amount of time it takes for the 1 ounce of water to completely evaporate.
-- Pour 1 ounce of water into a wide dish, with a large surface area. -- Set the dish in the second section of the box ... the one the air passes through just before it leaves the box. -- Start the fan. -- Count the amount of time it takes for the 1 ounce of water to completely evaporate.
***Show that the 1 ounce of water evaporated faster ***
when it had more surface area.
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Experiment B:
-- Again, pour 1 ounce of water into the wide dish with the large surface area. -- Again, set the dish in the second half of the box ... the one the air passes through just before it leaves the box. -- This time, place another wide dish full of water in the *first section *of the box, so that the air has to pass over it before it gets through the wall to the wide dish in the second section. Now, the air that's evaporating water from the dish in the second section already has vapor in it before it does the job. -- Start the fan. -- Count the amount of time it takes for the 1 ounce of water to completely evaporate.
***Show that it took longer to evaporate when the air ***
blowing over it was already loaded with vapor.
The proposed experiment illustrates the effects of surface area and vapor concentration on evaporation rates. The first experiment compares evaporation from dishes with different surface areas, while the second examines how trapped vapor affects evaporation. By measuring water levels over time, students can see firsthand how these factors influence evaporation rates.
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