Recycling Plastics Lab
Recycling Plastics Lab (1/8)
How can we separate plastics efficiently using the
differing densities of different types of plastics?
How do the 4 types of plastic in our sample rank in
terms of density?
What minimum concentration of salt water is
required to make each type of plastic float?
What is the density of the minimum concentrations
of salt water?
What is the density of each type of plastic based on
the minimum concentrations of salt water?
Initial Observations
Fill plastic cup ½ full with water.
Pour container of beads into water.
Use spoon to get all beads into water. (Rinse
container in sink to clean)
Stir beads in water with spoon.
Let 4 types of beads settle in cup.
Record appearance & behavior of all 4 types of
beads.
Recycling Plastics Lab (2/8)
• Hypothesis: If, then, because…
• If the concentration of salt water is increased,
then the density of salt water will ______,
because _____
• Materials: ziploc bag, plastic beads (4 kinds),
spoon, 50 ml graduated cylinder, plastic drink
cup, stir bar, electronic balance, plastic
condiment cup, plastic pipet
Recycling Plastics Lab (3/8)
General Directions:
Prepare a data table as follows:
1. Measure & record the mass of an empty graduated cylinder.
2. Fill the condiment cup ½ way with salt and record the total
mass of cup & salt.
Item
Mass of graduated cylinder
Mass of cup of salt at start
(remeasure each day)
Measurements
Observations
2. Weigh the empty
graduated cylinder
1. Weigh ½ full
condiment cup
of salt
3. Add 50.0
ml of water
6. Pour sample
of water into
graduated
cylinder
4. Add a spoon
full of beads
5. Remove
floating
beads
7. Record volume
& mass of sample
8. Return sample
liquid to plastic cup
9. Slowly add
salt until next
beads float
11. Record volume
& mass of sample
10. Pour sample
of water into
graduated
cylinder
12. Return sample
liquid to plastic cup
Recycling Plastics Lab (4/8)
3. Measure out carefully 50.0ml of tap water and
pour into the drinking cup.
4. Pour a spoonful of plastic beads into the water and
record how they behave.
5. Add small amounts of salt with the spoon and stir
until all dissolves and none settles to the bottom.
6. Observe & record the plastic beads to see if any have
begun to float without bubbles aiding them.
Recycling Plastics Lab (5/8)
8. a. If most of one type of bead is floating,
without bubbles, then record the 3
measurements below to allow you to
determine the concentration (slide 7) &
density (slide 8).
Item
Measurements
Observations
Mass of cup of salt
Mass of salt water
Volume of salt water
b. If beads don’t float, then add a little more
salt to dissolve. Repeat until most of one
type begin to float.
Recycling Plastics Lab (6/8)
9. Use a spoon and strainer to remove the floating type
of beads off of the top without removing water.
10. Continue to dissolve more salt until the amount of
salt needed to float each type of plastic is
determined.
11. Clean up by straining out the beads and rinsing them
with fresh tap water before returning them to the
capped jar.
12. Make sure each item from your kit is returned to the
ziploc bag at your table for the next class to use.
Recycling Plastics Lab (7/8)
Determine the concentrations of salt water that
floated each type of plastic by:
a. Record the mass of the condiment cup of salt to
see how much salt was used.
b. To determine the mass of salt used, subtract the
cup mass after floating from the starting mass of
the cup of salt.
c. Divide the mass of salt by the 50.0ml of water to
find a ratio of salt to water
Recycling Plastics Lab (8/8)
Determine the density of each floating ratio of
salt water.
1. When a type of plastic is mostly floating,
then strain out the beads from the top as you
fill the graduated cylinder at least half full.
2. Record the volume of the liquid in the
graduated cylinder.
3. Record the mass of the liquid in the
graduated cylinder.
4. Divide the mass by the volume for the liquid.
5. Return the liquid and the beads to the cup.
Recycling Plastics Lab Report (1/)
•
•
•
•
Title
Purpose (Relate the 5 questions to the title)
Materials
Variables – manipulated (C), responding (2),
controlled
• Hypothesis: If, then, because…
• If the concentration of salt water is increased,
then the density of salt water will ______,
because _____
Recycling Plastics Lab Report (2/)
Procedure:
Since the general procedures are provided for
you, summarize them in a paragraph making
sure you hit all the major parts.
Data & Observations:
Item / Step
Measurements
Observations
Break up into Day 1,
Day 2, Day 3. Be
specific about what you
are measuring or
observing.
Include units like grams
& milliliters. Make sure
your measurements are
all as precise as possible
as taught in class.
Describe what you saw
or noticed during the
lab – especially sources
of error.
Recycling Plastics Lab Report (3/)
Analysis – Calculations, Graphs, Sources of Error
a. Calculations:
Item
Formula
Work
Answer
Identify
specifically what
you are
calculating
Write a formula
with words or
variables how to
find the answer.
Show your
numbers and
units used in
calculating the
actual result.
Record your
answer with units
and appropriate
significant
figures.
Recycling Plastics Lab Report (4/)
Item
Formula
Work
Answer
Mass of salt for
___ plastic beads
Cup of salt at
start – cup of salt
when floated
35.63g – 32.15g
3.48g
Concentration of
salt water for
floating ___
beads
Mass of Salt
divided by
volume of water
3.48g / 50.0ml
0.696 g/ml
Mass of salt
water able to
float ____ beads
(Salt water +
graduated
cylinder) –
(graduated
cylinder
76.25g – 55.89g
20.36g
Density of salt
water able to
float ___ beads
Density = mass/
volume
20.36g / 19.8ml
1.03 g/ml
Recycling Plastics Lab Report (5/)
Analysis:
Graph Density vs Concentration of Salt Water
X – axis = Concentration (calculated answers)
Y-axis = Density (calculated answers)
3 Data Points expected from this lab.
Sources of Error:
Describe 2 or more certain issues which prevent
you from getting perfect results. How do they
affect your results – higher or lower values?
Recycling Plastics Lab Report (6/)
Conclusions:
1. Restate your hypothesis.
2. Evaluate your hypothesis and use calculated
values as evidence.
3. Answer the 5 questions from the beginning
of the lab.
4. Propose a process of separating recycled
plastics that you could patent based on your
findings.