The density of a piece of plastic from a broken car window was determined. The sample weighed 211 g and occupies a volume of 179 cm3.

1. The density of this plastic is
[ Select ]
0.85
2.11
1.18
1.79
3.78
g/cm3.

2. Based on the list of polymers below, the plastic is most likely made of
[ Select ]
PP
LDPE
HDPE
PS
PAN
PMMA
PLA
PET
PVC
PTFE
.

Polymer Abbreviation

Polymer Name

Density (g/cm3)

PP

polypropylene

0.900 – 0.910

LDPE

low density polyethylene

0.917 – 0.940

HDPE

high density polyethylene

0.940 – 0.970

PS

polystyrene

1.040 – 1.050

PAN

polyacrylonitrile

1.110 – 1.150

PMMA

polymethylmethacrylate/acrylic

1.170 – 1.200

PLA

polylactide

1.230 – 1.250

PET

polyethylene terephthalate

1.300 – 1.400

PVC

polyvinylchloride plasticized

1.350 – 1.700

PTFE

polytetrafluoroethylene

2.100 – 2.200

Question

The density of a piece of plastic from a broken car window was determined.  The sample weighed 211 g and occupies a volume of 179 cm3.

1.  The density of this plastic is 
[ Select ]
0.85
2.11
1.18
1.79
3.78
 g/cm3.

2. Based on the list of polymers below, the plastic is most likely made of 
[ Select ]
PP
LDPE
HDPE
PS
PAN
PMMA
PLA
PET
PVC
PTFE
 .

Polymer Abbreviation

Polymer Name

Density (g/cm3)

PP

polypropylene

0.900 – 0.910

LDPE

low density polyethylene

0.917 – 0.940

HDPE

high density polyethylene

0.940 – 0.970

PS

polystyrene

1.040 – 1.050

PAN

polyacrylonitrile

1.110 – 1.150

PMMA

polymethylmethacrylate/acrylic

1.170 – 1.200

PLA

polylactide

1.230 – 1.250

PET

polyethylene terephthalate

1.300 – 1.400

PVC

polyvinylchloride plasticized

1.350 – 1.700

PTFE

polytetrafluoroethylene

2.100 – 2.200

BlackTom AI · Accepted Answer

To tackle this problem, I’ll break down both parts step by step and compare each option.
First, determine the density from the given mass and volume: density = mass / volume = 211 g / 179 cm3.
Dividing 211 by 179 gives approximately 1.1799 g/cm3, which rounds to 1.18 g/cm3. This matches the provided correct density value of 1.18, so the density choice is 1.18.
Next, identify which polymer a density of about 1.18 g/cm3 points to among the listed polymers by comparing typical density ranges:
- PP (polypropylene): about 0.900–0.910 g/cm3. This is well below 1.18, so it’s not a match.
- LDPE (low-density polyethylene): about 0.917–0.940 g/cm3. Also too low.
- HDPE (high-density polyethylene): about 0.940–0.970 g/cm3. Still too low for our sample.
- PS (polystyrene): about 1.040–1.050 g/cm3. This is closer, but still significantly below 1.18.
- PAN (polyacrylonitrile): about 1.110–1.150 g/cm3. Close to 1.18, but typically a bit lower than PMMA, and our value sits at the upper end.
- PMMA (polymethylmethacrylate): about 1.170–1.200 g/cm3. This range encompasses 1.18 g/cm3, making PMMA a strong match.
- PLA (polylactide): about 1.230–1.250 g/cm3. Higher than our value, so less likely.
- PET (polyethylene terephthalate): about 1.300–1.400 g/cm3. Too dense compared to 1.18.
- PVC (polyvinyl chloride): about 1.350–1.700 g/cm3. Also too dense.
- PTFE (polytetrafluoroethylene): about 2.100–2.200 g/cm3. Much too dense.

Given the density of 1.18 g/cm3, the most consistent polymer is PMMA, and the closest range in the provided table is 1.170–1.200 g/cm3.

Why other options are not correct for the polymer identification:
- If you select PP, LDPE, or HDPE, you’d be choosing densities around 0.9–1.0 g/cm3, which clearly underestimates the measured density and would imply a lighter material than the sample.
- Choosing PS or PAN would be more plausible only if the measured density were around ~1.04–1.15 g/cm3; at 1.18, PMMA fits best.
- Selecting PLA, PET, PVC, or PTFE would imply densities significantly higher than 1.18 g/cm3 (or much higher in the case of PTFE), which contradicts the measured value.

In summary, the density calculation yields 1.18 g/cm3, and PMMA best matches the measured density within the listed density ranges, making both selections 1.18 and PMMA the most consistent choices.

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