Types of Chemical Reactions Chemical Reactions can be classified into 5 main categories. These categories makes it easier to determine the product of the reaction. The 5 categories are: Synthesis Reactions Decomposition Reactions Single Replacement Double Replacement Combustion Reactions

Synthesis Reactions Two or more reactants combine to make 1 new product. AB For example: C(s)+ O 2 (g) → CO 2 (g) So: A + B → H 2 O(l) + SO 3 (g) → H 2 SO 4 (aq)

Decomposition Reactions A single reactant breaks down to form 2 or more products. So: AB→ A + B For example: H 2 CO 3 (aq) →H 2 O(l) + CO 2 (g) CaCO 3 (s) →CaO(s) + CO 2 (g)

Single Replacements A single element replaces a similar element of an adjacent reactant compound. So: AB + C → AC + B For example: Zn(s) + CuSO 4 (aq) →ZnSO 4 (aq) + Cu(s)

Double Replacements Two ionic compounds exchange ions, producing 2 new ionic compounds. So: AB + CD → AD + CB For example: NaCl(aq) + AgNO 3 (aq) → NaNO 3 (aq) + AgCl(s) HCl(aq) + NaOH(aq) →NaCl(aq) + H 2 O(l)

Combustion Reactions A single element or compound combines with oxygen gas releasing energy. This rapid oxidation is called burning. C(s) + O 2 (g) → For example: CO 2 (g) + energy 2Mg(s) + O 2 (g) →2MgO(s) + energy Another type of combustion reaction are those that use Hydrocarbons.

CH 4 (g) +2O 2 (g) →CO 2 (g) + 2H 2 O(l) Hydrocarbons Compounds containing only the elements Carbon and Hydrogen. When these compounds combine with Oxygen they form Carbon dioxide gas and water vapour. For example: Burning Methane Burning Naphthalene C 10 H O 2 →10 CO 2 (g) + 4H 2 O(l)

Read chapter 5.5 Do, ‘Decomposing Powder’ Prac Answer Questions Your Turn: Open Science Quest 10 to chapter 5.5 ‘A World of Reactions’

Rates of Reactions The rates of a reaction depends on 4 things: 1. Temperature 2. Concentration 3. Size of Particles 4. Introduction of a catalyst

Temperature Temperature increases the rate number of collisions When the temperature is increased, the particles all more quicker, this causes more collisions. ColdHot

Concentration Concentration increases the number of collisions If the solution is made more concentrated it means there are more particles to react. More particles that are squashed together is going to cause more collisions Low High

Size of Particles Size of solid particles (or surface area) increases collisions If one of the reactants is a solid, then breaking it up into smaller pieces will increase the surface area. The larger the surface area, the more area the solution has to work on. Low High

Introducing a Catalyst Catalyst increase the number of collisions A catalyst works by helping bonds break more easily, therefore, the reactants need less energy to react. Different catalyst are used for different reactions They can give a surface for the reactants to stick to where they can collide into each other, increasing collision amounts. Draw diagram from Ch. 5.7

Read chapter 5.7 Do, ‘A liver catalyst’ Prac Answer Questions Open Science Quest 10 to chapter 5.7 ‘The need for speed’