01 Chemical Changes Lesson Objectives

Knowledge and skills

 Knowledge – At the end of this unit, students must understand that:

·         A chemical change is a process that produces a new substance. The particles of the substance are broken apart and the atoms are rearranged into new particles, forming a new substance.

·         Chemical changes are accompanied by a change in energy. When energy is given off during the reaction, the temperature increases. When energy is absorbed during the reaction, the temperature decreases.

·         Chemical changes may result in observations such as colour change, effervescence and/or formation of precipitate.

·         Acids turn blue litmus red, has a sour taste and a pH of less than 7.

·         Alkalis (soluble bases) turn red litmus blue, has a bitter taste and a pH of more than 7.

·         Bases are metal oxides and hydroxides. Alkalis are soluble bases.

Skills – At the end of this unit, students must be able to:

·         Identify different types of chemical changes. These include combination, combustion, decomposition, acids and base reactions and some biological reactions (photosynthesis and respiration).

·         Predict that products of a chemical reaction, given the reactants, and vice versa. Example: zinc + hydrochloric acid à zinc chloride + hydrogen gas.

·         Distinguish between physical and chemical changes.

·         Test for gases such as carbon dioxide, ammonia, hydrogen and oxygen.

·         Describe the test for carbon dioxide, ammonia, oxygen and hydrogen. For example, carbon dioxide is tested using limewater, where a white precipitate in limewater indicates the presence of carbon dioxide.

·         Describe chemical changes using word equations.