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 Measurements Observations

Mass of graduated cylinder

Mass of cup of salt at start (remeasure each day)

1. Weigh ½ full condiment cup of salt

2. Weigh the empty graduated cylinder

3. Add 50.0 ml of water

4. Add a spoon full of beads

5. Remove floating beads

6. Pour sample of water into graduated cylinder

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).

b. If beads don’t float, then add a little more salt to dissolve. Repeat until most of one type begin to float.

Item Measurements Observations

Mass of cup of salt

Mass of salt water

Volume of salt water

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 Errora. 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 WaterX – 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.