Chemical changes are occurring around us all the time Food cooking Fuel being burned in a car s engine Oxygen being used in the human body
The starting materials are called reactants The ending materials are called products
To describe the reaction that creates fire at the bunsen burner in lab Methane gas reacts quickly with oxygen gas to produce fire, carbon dioxide, and water vapor That s a lot to write!
We can simplify the description of our reaction by using a word equation Methane gas + oxygen gas fire + carbon dioxide gas + water vapor Still a lot to write!
There is an even simpler way to express a chemical reaction We use formula equations to show the reaction Methane gas + oxygen gas fire + carbon dioxide gas + water vapor CH 4 + O 2 CO 2 + H 2 O + represents and represents yields
Methane gas + oxygen gas fire + carbon dioxide gas + water vapor CH 4 + O 2 CO 2 + H 2 O However there is some information that is not shown in the formula equation State of matter Fire/ Energy
We can show state of matter using the following symbols (s) solid (l) liquid (g) gas (aq) aqueous solution (substance is dissolved in water) Methane gas + oxygen gas fire + carbon dioxide gas + water vapor CH 4 (g)+ O 2 (g) CO 2 (g) + H 2 O (g)
We can indicate if energy was present in the reaction Reactions that have energy as a reactant are called endothermic They require energy for the reaction to occur Heat Also sometimes represented as or Reactions that have energy as a product are called exothermic Energy happens as a result of the reaction
Methane gas + oxygen gas fire + carbon dioxide gas + water vapor CH 4 (g)+ O 2 (g) CO 2 (g) + H 2 O (g) + energy
Hydrogen plus oxygen yields water. Nitrogen plus hydrogen yields ammonia. Aluminum bromide plus chlorine yields aluminum chloride and bromine.
Hydrochloric acid plus sodium hydroxide yields sodium chloride plus water. Iron plus lead (II) sulfate react forming iron (II) sulfate and lead. Potassium chlorate when heated produces potassium chloride plus oxygen gas.
Sulfuric acid decomposes to form sulfur trioxide gas plus water. Sodium oxide combines with water to make sodium hydroxide. Potassium iodide reacts with bromine forming potassium bromide plus iodine.
Sodium phosphate reacts with calcium nitrate to produce sodium nitrate and calcium phosphate. Zinc reacts with iron (III) chloride yielding zinc chloride plus iron precipitate. Ammonium carbonate and magnesium sulfate react to yield ammonium sulfate plus magnesium carbonate.
Phosphoric acid plus calcium hydroxide react forming solid calcium phosphate plus water. Aluminum plus oxygen form aluminum oxide under certain conditions. Nitrogen plus oxygen gas react and form dinitrogen pentoxide.
The five general types of reactions: Synthesis Decomposition Single-replacement Double-replacement Combustion
A synthesis reaction is a chemical change in which two or more substances react to form a single new substance. A + B AB 2Mg + O 2 2 MgO
A decomposition reaction is a chemical change in which a single compound breaks down into two or more simpler products AB A + B 2NaN 3 2Na + 3N 2
A single-replacement reaction is one in which one element replaces a second element in a compound AB + C AC + B 2NaCl + Br 2 2NaBr + Cl 2 or C + AB A + CB Zn + Cu(NO 3 ) 2 Cu + Zn(NO 3 ) 2
A double-replacement reaction which is a chemical change involving an exchange of positive ions between two compounds. AB + CD AD + CB 2NaNO 3 + CuBr 2 2NaBr +Cu(NO 3 ) 2
A combustion reaction is a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light. CH 4 + 2O 2 CO 2 + 2H 2 O