Foundational and Learning Objectives

CR1 Observe common chemical reactions in your world

Suggested time: 4-6 hours

Learning Objectives

1. Provide examples of how science and technology are an integral part of our lives and community. (TL)
   
2. Observe and describe chemical reactions that are important in everyday life.
   
3. Perform activities to investigate exothermic and endothermic chemical reactions.
   
4. Identify indicators that provide evidence that a chemical reaction has likely taken place.
   
5. Show concern for safety and accept the need for rules and regulations when conducting scientific investigations.
   
6. Demonstrate knowledge of Workplace Hazardous Materials Information System (WHMIS) standards by selecting and applying proper techniques for handling and disposing of lab materials.
   
7. Show concern for safety and accept the need for rules and regulations. (PSD)
   
8. Use scientific principles to describe the functioning of domestic or industrial technologies.
   
9. Identify examples of technologies or technological processes that were developed based on scientific understanding of chemical reactions. (TL)
   
10. Identify and describe science and technology-based occupations related to chemistry and explore the educational and training requirements of these occupations. (CD 5.3)
    
11. Compare examples of how society supports and influences science and technology in Saskatchewan and Canada .
    

Key Questions

1. What is the difference between physical and chemical changes?
   
2. What indicators might provide evidence that a chemical reaction has occurred?
   
3. What are some common chemical reactions that take place in your life?
   
4. What are some common chemical reactions that take place in Saskatchewan agriculture and industry?
   
5. What is the purpose of the WHMIS?
   
6. What is the purpose of a Material Safety Data Sheet (MSDS)?
   

Key Concepts

• A chemical reaction is a process that involves the formation of new substances with new properties.
  
• Reactants are substances that undergo change in a chemical reaction.
  
• Products are substances that form in a chemical reaction.
  
• Indicators that provide evidence that a chemical reaction might have taken place include: a colour change, an odour change, the formation of a new substance (precipitate), the emission of a gas, and the release or absorption of heat or light.
  
• Energy is lost (released) or gained (absorbed) in every chemical reaction.
  
• In an exothermic chemical reaction, energy is released to the surroundings.
  
• In an endothermic chemical reaction, energy is absorbed from the surroundings.
  
• Observing and describing, using our senses, are basic processes of science.
  
• Inferring is explaining an observation in terms of previous experience.
  
• Scientific knowledge is generated by, and used for, asking questions concerning the natural world.
  

Pre-Instructional Questions

1. Are the students able to identify the physical properties of a substance?
   
2. Do students understand the difference between physical and chemical changes?
   
3. Are the students able to identify characteristics that indicate a physical change might have taken place?
   
4. Are the students able to identify characteristics that indicate a chemical change might have taken place?
   
5. Are the students able to identify the products and reactants when observing chemical reactions?
   
6. Are students aware of the Workplace Hazardous Materials Information System (WHMIS) and similar safety symbols and their meanings?
   
7. Are the students aware of common chemical reactions in Saskatchewan agriculture and industry?
   

Suggested Teaching Strategies and Activities

1. Students should observe a variety of physical and chemical changes among common substances. Examples might include: steel wool placed in copper (II) sulfate solution, oxidation of iron (rusting), ice melting, Alka-Seltzer tablet added to water, combustion of wax, vinegar added to milk, cutting of paper, toasting of bread, vinegar added to baking soda, a match burning, leaves changing colour in the fall, phenolphthalein added to sodium hydroxide, composting of organic waste, decomposition of hydrogen peroxide, etc. Students should describe the properties of each substance before and after the change for each reaction. Students should look for indicators that could provide evidence that a chemical reaction has occurred rather than a physical change. Students should be able to identify the products and reactants of each chemical reaction. Students should demonstrate safe practices throughout the investigations.
   
   
2. Students should describe the function of the Workplace Hazardous Materials Information System (WHMIS). This includes describing WHMIS hazard categories and symbols, and the function of Material Safety Data Sheets (MSDS). Students should also describe the Hazardous Household Product Symbols. Students should discuss why it is necessary to have national standards such as WHMIS and Canadian Standards Association (CSA). (Note: as of October 1, 2001, Health Canada only requires two frames (triangle and octagon) to indicate the degree of hazard of household products. Many current resources show a third frame (diamond) which is no longer in use.) (PSD)
   
   
3. Students could classify a list of chemical reactions as endothermic or exothermic, based on either written descriptions of the reactions or direct observations of the reactions. Students could suggest where or how the reaction releases or absorbs energy (e.g., a firecracker exploding releases energy as sound, light, and heat). (CCT)
   
   
4. Students should investigate common chemical reactions in order to identify which reactions absorb energy (endothermic) and which release energy (exothermic). Examples of materials that are simple and safe to use include: hot packs and cold packs, citric acid and sodium bicarbonate (baking soda), or vinegar and steel wool. (Note: Energy changes are a key concept in the Weather Dynamics unit, but those changes are generally due to changes of state, not chemical reactions.)
   
   
5. Students could generate a list of products that are used during any given day. Students could choose a product, or category of products, and research the manufacturing process, identifying the chemical reactions that occur during the process. Student responses could include an analysis of how their lives would be different without these products. Examples of categories and products for research include: auto products (brake fluid, de-icer, grease, tires), household cleaners (bleach, ammonia, fabric softener, furniture polish, glass cleaner), pesticides, pet care products (flea and tick treatment, kitty litter, fish tank cleaner), personal care products (makeup, shampoo, hair colouring, fragrances, mouthwash, toothpaste), home construction and maintenance products (glue, grout, insulation, paint, putty, stain, caulk), and arts and crafts products (fabric dye, paint thinner, epoxy glue, repositionable glue, wood filler).
   
   
6. Students could identify common chemical reactions that occur in Saskatchewan agriculture and industry. Examples can be found in: potash mining, fertilizer production, gold mining, oil exploration, recycling, welding, pulp and paper production, plastics manufacturing, synthetic textiles, water treatment, waste water treatment, diamond mining. It is not necessary at this point that students understand all of the reactions that take place within any of these processes, but students should recognize that chemical reactions take place throughout the agricultural and industrial sector in Saskatchewan and that these reactions are often complex. The top chemicals produced industrially in Canada are: sulphuric acid, nitrogen, oxygen, ethylene, calcium carbonate, ammonia, sodium hydroxide, propylene, and sodium carbonate.
   
   
7. Students could gather information about chemistry-related occupations in Saskatchewan . Research could focus on a specific sector (agriculture, mining, forestry, and manufacturing) or an occupation (technician, laboratory technologist, scientist, sales manager). Appropriate information to collect might include: the education required for these occupations, job prospects, salaries, types of skills required, job titles, numbers of positions, major employers, and locations. Students might choose to interview members of their community whose occupation requires some knowledge of chemistry. ( SaskNetWork.ca provides information specific to careers in Saskatchewan .) (CD 7.3)