SNC1D CHEMISTRY ATOMS, ELEMENTS, & COMPOUNDS L Introduction (P.130-133) What makes a chewing gum so good? Is it the taste, the texture, or the size of the bubble you can blow? People have been chewing gum for thousands of years. Stone Age people chewed birch bark tar, which forms when the bark is heated. Native peoples of North America chewed the sap of spruce trees. 1 Today, the chewy, rubbery substance in gum no longer comes form natural sources. Instead, it is a synthetic material made form the chemicals found in oil. The scientists who develop these synthetic gum bases design them for the type of gum that they want to make. For example, the gum bases used for regular chewing gum have different properties than those used in bubble gum, which needs to be more elastic. 2 1
But there are more substances in gum than just the rubbery stuff. Look at the ingredients on the package. Carnauba wax, for example, is an ingredient in many types of chewing gum. It comes from tree leaves, and it gives the gum a dry, shiny coating. Carnauba wax is also found in car wax, shoe polish, and dental floss! Shellac, which comes forma type of insect, is used to give wood furniture a polished finish. It is also used to give many types of chewing gum a shiny appearance. 3 Substances are added for flavouring. For example, sorbic acid and malic acid give gum a sour apple flavour. Chocolateflavoured chewing gum cannot be made because the cocoa butter in chocolate makes the gum too soft to be chewed. 4 UNIT Preview In this unit, you will: 1. assess social, environmental, and economic impacts of the use of common elements and compounds, with reference to their physical and chemical properties; 2. investigate, through inquiry, the physical and chemical properties of common elements and compounds; 3. demonstrate an understanding of the properties of common elements and compounds, and of the organization of elements in the periodic table. 5 2
1. Which states of water are shown in the photo below? 6 2. Describe the differences between a solid and a liquid. 7 3. What are the particles in the liquid doing as the liquid evaporates? 8 3
4. Classify each of the following as either a pure substance or a mixture: (a) hot chocolate (b) distilled water (c) oxygen (d) sugar dissolved in water (e) pizza M P P M M 9 5. Answer the following questions. (a) Which is more viscous, water or ketchup? (b) Which is denser, wood or steel? (c) Which has more mass, one kilogram of lead or one kilogram of wool? (d) Which has a greater volume, a volleyball or a baseball? (a) water (b) steel (c) both have a mass of one kilogram (densities are different) (d) volleyball 10 6. Liquid flowing into the stream in the photo comes from an abandoned farm. What possible environmental effects could this have? Give reasons for your answer. 11 4
7. Batteries contain heavy metals (such as nickel, cadmium, and lead) and are responsible for over 50% of the heavy metals found in landfills. Why should batteries be recycled instead of being discarded? 12 8. The following diagram shows two students performing an experiment in the lab. Find at least five lab safety errors. 13 9. Give reasons for the following safety procedures. (a) Wash your hands after handling chemicals. (b) Close the containers of unused chemicals promptly after use. (c) Read the safety labels of all chemicals you use. (d) Check with your teacher before disposing of chemicals in the sink. (e) Never pour unused chemicals back into the stock bottle. 14 5
10. A block of wood has a density of 0.95 g/cm 3. Will it float or sink when placed in a liquid with a density of: (a) 1.00 g/ml? (b) 0.88 g/ml? Explain your answer. (a) the wood will float since its density is < 1.00 g/ml (b) the wood will sink since its density is > 0.88 g/ml 15 11. You are heating a 500 ml solution in a glass beaker and recording its temperature every 2 min during an experiment. What is your: (a) independent variable? (b) dependent variable? (c) control variable(s)? (a) time (i.e. variable being manipulated or changed) (b) temperature (i.e. variable being observed or measured) (c) volume & container (i.e. variable(s) being controlled) 16 Activity: Plastic World (B1/P.132) ISSUE We use plastics for a multitude of uses. We also use plastic bags to carry groceries, package food, and contain garbage. So why should plastics and plastic bags be of such a concern to us? INSTRUCTIONS A. Read the article B1: Plastic World. B. Answer Q.1-3/P.133 C. As a class/group, discuss/compare your answers. 17 6