Chemical Reactions Mr. Skirbst Physical Science Topic 16

Chemical Reactions A process that changes the physical and chemical properties of substances to form new substances

Indicators of a Reaction -Gas produced -Color change -Light released -Heat absorbed / released -Change in properties

Chemical Equations -Shorthand for chemical reactions Magnesium metal plus oxygen gas yields magnesium oxide

Law of Conservation of Mass -Matter cannot be created or destroyed, only changed in form

Balancing Equations MUST be done to keep LAW * The # of atoms of each element in the reactants and the products MUST BE equal to one another! * ONLY coefficients may be altered

Steps for Balancing Equations 1.Identify elements in reactants/products

Steps for Balancing Equations 1.Identify elements in reactants/products 2.Count # atoms of each

Steps for Balancing Equations 1.Identify elements in reactants/products 2.Count # atoms of each 3.If not balanced, change coefficients

Steps for Balancing Equations 1.Identify elements in reactants/products 2.Count # atoms of each 3.If not balanced, change coefficients 4.Repeat #’s 2 & 3 until balanced

Steps for Balancing Equations 1.Identify elements in reactants/products 2.Count # atoms of each 3.If not balanced, change coefficients 4.Repeat #’s 2 & 3 until balanced After each, ask “have you broken the law?” It is balanced only when you can answer “no” to each question.

4 Types of Chemical Reactions 1.SYNTHESIS

4 Types of Chemical Reactions 1.SYNTHESIS - two or more simple substances combine to form a new, more complex substance

4 Types of Chemical Reactions 1.SYNTHESIS - general format: A + B  C ie. Na + Cl  NaCl

4 Types of Chemical Reactions 2.DECOMPOSITION - a complex substance breaks down into two or more simpler substances

4 Types of Chemical Reactions 2.DECOMPOSITION - general format: C  A + B ie. H 2 CO 3  H 2 O + CO 2