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Puddles disappear overtime, where does the water go?
Rain falls from the sky, how does it get there?
Water evaporates, turns from a liquid to a gas. This happens rapidly at waters boiling point 100oC, but it also happens at lower temperatures, just not so quickly.
Evaporation occurs when the top layer of the liquid gains enough energy to escape as a gas into the air. Evaporation of water does not need as much heat energy as is needed to boil water
OC2 separate mixtures using evaporation
Apparatus
Method
- Find the mass of an empty clean evaporation dish
- Find the mass of an evaporation dish with water in it
- Place a beaker of hot water on a gause on a tripod
- Set up the evaporation dish on a beaker of hot water
- Heat the beaker using a Bunsen burner
- When the Evaporation dish goes dry stop and allow cool
- Remeasure the mass of the dish.
Calculations
If we have a sample of water that has other substances dissolved in it we can see how much of these substances are dissolved if we evaporate off the water. This separates the water from the substances but the water is not collected
Results
Find the mass of an evaporating dish = _______ g (a)
Add a sample of water of which you want to know the dissolved solids in
Measure the mass of a sample of water + evaporating dish = _______ g (b)
Find the mass of the water added = _______ g (c) = (b) - (a)
evaporate the water
measure the mass of the dish now, the dish should be more massive than before
Mass of Evaporating dish and dissolved solids = ______ g (d)
calculate the mass of the dissolved solids (last mass - 1st mass) = _______ g (e) = (d) - (a)
Calculate the percentage dissolved solids in the sample
to do this we need to fill in and use the following formula
(e) / (c) x 100 %
Calculations
mass of suspended solids.
Suspended solids % = ────────────────── × 100%
mass of water
Now allow the sample to evaporate off all the water.
Percentage Dissolved Solids =
mass of suspended solids.
Suspended solids % = ────────────────── × 100%
mass of water
Conclusion
We can use Evaporation to separate a Soluble Solid from a Solvent. A substance that is dissolved in a liquid, like salt in water.
How do you think we could speed up this process?
Gas fire
cooker hob
microvave
Separating a dissolved Solution by Evaporation
Distillation is the recondensing of evapourated water, to purify it
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