How much has the weight of plastic bottles changed?

Grade level: 3rd – 5th grades

Skills: Division 

Related environmental issues: Reduce /  Reuse / Recycle

The average weight of  plastic beverage bottles has changed over time. In 1980, five empty 2-liter PET bottles weighed 340 grams.  Now, nine 3-liter PET bottles weigh 378 grams.

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  1. Which weighs more, a plastic bottle in 1980 or now? And how much?
  2. Why do you think has the weight of plastic bottles changed? Explain.

Sources: PET Resin Association, Little-Known Facts about PET Plastic

 

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Answer keys

  1. 1980 bottle: 340 ÷ 5 = 68 (g)   Now: 378 ÷ 9 = 42 (g)    68 – 42 = 22 (g)     A plastic bottle now is 22 g lighter than that in 1980.
  2. Answers may vary: Hint 1) Lightweight plastic bottles reduce the use of plastic and raw materials  2) Lightweight plastic bottles reduce overall weight of the item and reduce energy consumed and CO2 emitted in the process of manufacturing and transporting the item. 3) Lightweight plastic bottles reduce plastic (and raw materials) use, so does the amount of plastic that has to be recycled.

 

SOLAR ENERGY IN THE US

Grade level: 3rd – 5th grades

Skills: Addition & Subtraction (Decimal numbers)

Related environmental issues: Energy /  Renewable Energy

The table below shows shows how much new solar power was installed the United States each year between 2008 and 2017. Solar power means electricity generated by solar panels.

1 Gigawatt = 100,000,000 kilowatts (With 1 gigawatt of solar power, we can power 190,000 homes!)

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1. Which year has the largest number?

2. What is the difference between the numbers of the years 2014 and 2015?

3. Is the amount of solar panels installed in 2011 more than those installed in 2009 and 2010 combined or less?

4. What is the difference between the largest number and the smallest number?

5. Which year has the number 4.4 larger than  0.38?

6. Which two numbers make the largest value when added?

Sources:

 

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Answer keys

  1. 2016
  2. 7.5 – 6.24 = 1.26
  3. More : 1.92 > (0.38 + 0.85)
  4. 15.13 – 0.3 = 14.83
  5. 2013
  6. 15.13 and 10.61