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Leather or Synthetic? Soccer Balls for a Rainy Season

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Leather or Synthetic? Soccer Balls for a Rainy Season

Trace ball materials to natural resources and weigh their effects on society.

What a soccer ball is made of

Read the passage. Then answer the questions.

Heavy Balls on Rainy Saturdays

1The Lakeside youth soccer league plays every Saturday from September to November, rain or shine. Seventh graders Oskar Halloran and Adwoa Boateng volunteer in the league's equipment shed with Coach Imelda Barrientos. Last fall, many players complained that on rainy days some of the old match balls felt heavy and stung when they were kicked. Coach Barrientos asked Oskar and Adwoa to find out which kind of ball the league should buy next.

2A soccer ball has two main parts: an outer cover and an inner bladder that holds the air. About a hundred years ago, most balls had a leather cover, made from cowhide, stitched around a bladder of natural rubber. Natural rubber comes from latex, a milky sap collected from rubber trees. Today, most match balls have a cover of polyurethane (PU), a synthetic leather, or of polyvinyl chloride (PVC). Many bladders are now made of butyl rubber, a synthetic rubber.

3Synthetic materials are made when substances taken from natural resources react to form new substances. To make PU, small molecules made from crude oil or natural gas react and link into long chains. PVC is made from natural gas or crude oil and from ordinary salt, which supplies its chlorine atoms. Butyl rubber is made from small molecules that come from crude oil or natural gas.

4Synthetic balls have changed the game in many places. They often cost less than leather balls, so schools and leagues around the world can afford more of them, and they keep about the same weight in the rain. Synthetic materials also have costs. Crude oil and natural gas cannot be replaced once they are used up. Worn-out synthetic balls usually end up in landfills, where the plastics break down very slowly. Making and burning PVC must be done with care, because it can release harmful gases.

5For their test, Oskar and Adwoa took one ball of each kind from the shed. They pumped each ball to the same pressure and weighed it dry. They soaked each ball in a tub of water for 30 minutes, wiped it with the same towel and weighed it again. After the balls dried, the students pumped them to the same pressure once more, left them on a shelf for 7 days and measured how much of the pressure was left (Table 1).

1.
Use paragraphs 2 and 3. Match each ball part to the natural resource it is made from.
2.
Adwoa says, "PVC should count as a natural material, because salt is dug out of the ground." Which reply fits paragraph 3 best?
Question 2 options

The soak and air test

Use paragraph 5 and Table 1 to answer the questions.

Table 1. One Ball of Each Kind (air pressure left after 7 days)
BallCoverBladderDry mass (g)Mass after soak (g)Air pressure left (%)
1LeatherNatural rubber43050570
2PUButyl rubber42543195
3PVCButyl rubber42042396
4PUNatural rubber42543272
3.
Use Table 1.

During the soak, Ball 1 gained g of water, and Ball 3 gained g of water.

4.
Use Table 1. Round to the nearest whole percent.

The water Ball 1 gained was about % of its dry mass.

5.
Which two balls best show that the leather cover, and not the bladder, made a ball soak up more water?
Question 5 options
6.
Which conclusion about holding air does Table 1 support best?
Question 6 options
7.
Oskar and Adwoa tested only one ball of each kind. Which change would make their conclusions more trustworthy?
Question 7 options

Weighing the choices

Use paragraph 4, Table 1 and Table 2 to answer the questions.

Table 2. Supplier Information for Each Kind of Ball
BallPrice per ballLasts about
1 (leather, natural rubber)$602 seasons
2 (PU, butyl rubber)$303 seasons
3 (PVC, butyl rubber)$121 season
4 (PU, natural rubber)$283 seasons
8.
The league needs 40 balls. It buys a full new set of 40 balls each time a set wears out. Plan for 6 seasons.

Buying Ball 3 for 6 seasons would cost $. Buying Ball 2 for 6 seasons would cost $.

9.
Underline each statement that describes an effect of synthetic balls on society or the environment.

10.
Which ball should the league buy for its rainy fall Saturdays? Write a claim. Use data from Table 1 and Table 2 as evidence. In your reasoning, name the natural resources your ball is made from and describe one benefit and one cost of that choice for society or the environment.