Matter and Chemical Change Science 24: Unit A - Section 1

In this Unit you will learn about: Useful Chemistry – pesticides, synthetic fibres and polymers (nylon, plastic), alloys (Section 1) Useful Reactions – combustion, neutralization, exothermic and endothermic reactions (Section 2) Types of Chemical Reactions – word equations, balancing equations, naming compounds (Section 3) Reactions and the Environment - global climate change, air pollution, incomplete combustion, corrosion (rusting) (Section 4)

Chemistry Then and Now THEN NOW Farming Cooking/Baking - Pull weeds and kill insects by hand, - Horse drawn tractors, - Lots of manual labour Pesticides, tractors (gasoline), fertilizers, automatic feeders and barn cleaners Cooking/Baking - Made own soap with ashes from cooking stove and beef fat - Used crude pots and pans which rusted easily - Fire ovens only - Modern soap made with plant oils (Soap has two ends. One dissolves in water and one dissolves in grease) - Stainless steel utensils and pots, non-stick Teflon pots

Chemistry Then and Now THEN NOW Your life (early 1900s) - coloring your hair - color of your clothing - clothing fabrics (nylon, polyester) - food – margarine - cleaning – detergent

Now we will highlight the following four industries in greater detail and see how discoveries in chemistry have changed them: Farming Industry Clothing Industry Metal Industry (cooking and jewellery) Plastics Industry

Farming Practices Pesticides – substances that use chemicals to kill plants or animals Herbicides – chemical that kills particular plants Insecticide – chemical that kills particular insects

Clothing Industry Natural Fibres – cotton, wool, silk, flax i.e. stems of the flax plant were processed into threads that were woven to make linen Synthetic Fibres – nylon, polyester, Gore-tex, Kevlar (man-made fibres) Nylon is made from coal, water and air. Scientists used it as a toy initially to see how far they could stretch it. In 1939, nylon was used to make stockings. Now there are thousands of materials made with nylon. Polyester – doesn’t need ironing because it bounces back into shape quickly. It quickly became a very popular fabric for clothing.

Metal Industry Alloys – 2 or more metals mixed together; looks like one metal Alloys have the properties of the original metals that make up the alloy Examples: Stainless steel utensils – mixture of iron, chromium, nickel and carbon This combination of metal gives the utensils strength and durability but prevents them from rusting Jewellery – silver and copper are mixed in gold jewellery to provide strength; pure gold is very soft and damages easily Brass – is an alloy made of copper and zinc; musical instruments Cars – steel in today’s cars are mixed with chromium. The steel has the strength and durability and the chromium is resistant to rusting

Plastic Industry In one minute – list as many products as you can think of that are made of plastic. Five people with the longest lists will get a prize.

Polymers revolutionized the Plastics Industry Polymer – giant molecule made up of many small and identical sub-molecules

Plastic Industry Polymers - can be both natural or synthetic Natural Polymers – silk in spider webs, or sap from rubber trees Synthetic Polymers – human-made materials such as polystyrene (Styrofoam), neoprene (wetsuits), polyurethane (clothing), polyethylene (milk jugs), nylon, rubber, polyester, Kevlar, Gore-tex

Now let’s make our own polymer What your group of 2 will need: Disposable cup Stirring rod Graduated cylinder (10 mL) 5 mL white glue 5 mL of water 10 mL of Borax

Instructions: 1) Mix 5 mL of water with 5 mL of white glue in a disposable cup 2) Add 10 mL of borax solution to the glue mixture and stir for 2 min. 3) Roll the lump in your hands until it is not sticky anymore 4) Throw away your disposable cup, clean the remainder of your materials and return to the place where you found them 5) Go to pg. 10 and in the yellow box complete the “What Did You Find Out” Questions. You can do these questions together in your group of 2-3. 6) Hand in your questions when finished. Remember to put your names on the sheet.

What did you find out? 1. a) Reshape the putty into at least 3 forms, b) What happens when you try to bounce or stretch the putty? c) What else can you do with it? 2. How have the physical characteristics of the substances changed throughout the activity? 3. This product was around for a long time before anyone thought of using it as anything except a toy. Suggest two or three other uses for it.

Today’s Summary What is the difference between an insecticide and a herbicide? Name 3 types of synthetic fibres. Why do we make and use alloys ? List three examples of a synthetic polymer and explain where each one could be used.