Pre-Lab Questions: “Foul Water” Lab
Apalachee High School, Chemistry
1. What three water purification techniques will you use?
2. Define “filtration.”
3. Define “filtrate.”
4. What will you use to measure the volume of your foul water sample?
5. How do you support a funnel?
6. Oil and water separate into distinct layers. Which substance will you drain out of the funnel?
7. After separation, what will you do with the oil portion?
8. After separation, what will you do with the water portion?
9. How will you make a sand filter?
10. Why should the sand and gravel be pre-moistened?
11. What is the purpose of charcoal adsorption?
12. If your filtrate has bits of charcoal in it what do you do?
13. What do you do with your purified water?
14. What is the last thing you must do before leaving the lab?
Lab-Foul Water
Apalachee High School, Chemistry
Purpose
Purify a sample of “foul water”
Background
Three purification procedures will be used: (1) oil-water separation, (2) sand filtration, and (3) charcoal
adsorption/filtration. (Filtration is a general term for separating solid particles form a liquid by passing the
mixture through a material that retains the solid particles. The liquid collected after filtration is called the
filtrate.)
Safety Precautions
Do not taste the foul water samples under any circumstances. Wear safety goggles at all times.
Materials:
Ruler
100 mL graduated cylinder
2 beakers (100 mL)
1 Erlenmeyer Flask (250 mL)
Ring Stand w/ Ring
Funnel
Clay triangle
Filter Paper
Paper clip or Pushpin
Paper or Plastic cup
Dropper
Conductivity Tester
Lab Apron (optional)
Procedure
1. Obtain approximately 100 mL of foul water, provided by your teacher. Measure its volume precisely
with a graduated cylinder: record the value (with units) in your data table.
2. Examine the properties of your sample: color, odor, clarity, presence of solids or oily regions. Record
your observations in the “Before treatment” section of your data table.
Oil-Water Separation
Oil and water do not noticeably dissolve in each other. If oil and water are mixed and left undisturbed, two
layers form-the oil floats on top of the water.
1. Place a funnel in a clay triangle supported by a ring clamp and ring stand. Attach a rubber hose to the
funnel tip as shown in Figure 2.
2. Close the rubber tube by nipping it with your fingers (or by using a pinch clamp). Shake or stir the foulwater sample. Then pour about half the sample into the funnel and let it stand for a few seconds until the
liquid layers separate. (Gentle tapping may encourage oil droplets to float free.)
3. Carefully open the tub to release the lower layer into to 150-mL beaker. When the lower layer has
drained out, quickly close the rubber tube.
4. Drain the remaining layer into a second 150-mL beaker.
5. Repeat steps 2-4 using the remainder of your sample, adding each liquid to the correct beaker.
6. Dispose of the top, oily layer as instructed by your instructor. Observe the properties of the remaining
layer and measure its volume. Record your observations and data. Save the water sample for the next
procedure.
7. Wash the funnel with soap and water.
Sand filtration
A sand filter traps solid impurities that are too large to fit between sand grains.
1. Using a straightened paper clip, poke small holes in the bottom a paper cup (Figure 3).
2. Add pre-moistened gravel and sand layers to the cup as shown in Figure 4. (The bottom gravel prevents
the sand from washing through the holes. The top gravel keeps the sand from churning up when the
sample is poured in.)
3. Gently pour the sample to be filtered into the cup. Catch the filtrate (filtered water) in a beaker as it
drains through.
4. Dispose of the used sand and gravel according to your instructors instructions. Do not pour sand or
gravel into the sink!
5. Observe the properties and measure the volume of the water. Record your results. Save the water sample
for the next procedure.
Charcoal Adsorption/Filtration
Charcoal absorbs (attracts and holds on its surface) many substances that could give water a bad tastes, odor, or
cloudy appearance. Fish tanks include charcoal filters for the same purpose.
1. Fold a piece of filter paper as shown in Figure 5.
2. Place the folded filter paper in the funnel. Wet the paper slightly so it adheres to the funnel cone.
3. Place the funnel in a clay triangle supported by a ring clamp (see Figure 2). Lower the the ring clampl so
the funnel stem extends 2-3 cm inside a 150-mL beaker.
4. Place one teaspoon in a 125- or 250-mL Erlenmeyer flask.
5. Pour the water sample into the flask. Shake vigorously. Then gently pour the liquid through the filter
paper. Keep the liquid below the top of the filter paper—no liquid should flow between the filter paper
and the funnel.
6. If the filtrate is darkened by small charcoal particles, refilter the liquid. Use a clean piece of moistened
filter paper.
7. When you are satisfied with the appearance and odor of your purified water sample, pour into a gradated
cylinder. Observe and record the properties and the final volume of the sample.
8. Wash your hands thoroughly before leaving the laboratory.
Data Table
Color
Clarity
Odor
Presence of Oil
Presence of
Solids
Before Treatment
After oil-water
separation
After sand filtration
After charcoal
absorption/filtration
Calculations
Complete the following calculations. Record your work and answers in your notebook.
1. What percent of the original foul-water sample did you recover as “pure” water?
Percent of water purified = (vol. of water purified/vol. of foul-water sample) x 100 %
2. What volume of liquid did you lose during purification?
3. What percent of your original foul-water sample was lost during purification?
4. What does sand filtration remove from a dirty waters ample?
5. What does charcoal adsorption/filtration remove from a dirty water sample?
Volume