? Chemical Reactions

? Observing Chemical Reactions Evidence: 1)The colour changes 2)Bubbles A gas is produced 3)The mixture gets hotter (EXOTHERMIC) or colder (ENDOTHERMIC) 4) A solid (PRECIPITATE) forms from two aqueous solutions

? Observing Chemical Reactions Evidence: 1)The colour changes 2)Bubbles A gas is produced 3)The mixture gets hotter (EXOTHERMIC) or colder (ENDOTHERMIC) 4) A solid (PRECIPITATE) forms from two aqueous solutions Dissolved in water

? Demo’s What evidence is there that a chemical reaction has occurred?

? Representing Chemical Reactions In a chemical reaction, one or more substances change to produce new substances. The starting materials are called REACTANTS and the materials you finish with are called the PRODUCTS. A plus + sign is used between a list of different reactants and products. An arrow  is used between the reactants and products to show that the reactants get turned into the products.

? Word Equations A word equation describes a chemical reaction using the names of the reactants and products. Examples: Hydrogen + Oxygen  water Acetylene + oxygen  carbon dioxide + water

? Word Equations A word equation describes a chemical reaction using the names of the reactants and products. Examples: Hydrogen + Oxygen  water Acetylene + oxygen  carbon dioxide + water Reactants Products

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 1) Aluminum metal combines with chlorine gas to make aluminum chloride.

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 1)Aluminum metal combines with chlorine gas to make aluminum chloride. aluminum + chlorine  aluminum chloride

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 2) Magnesium metal combines with nitrogen gas to make magnesium nitride.

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 2) Magnesium metal combines with nitrogen gas to make magnesium nitride. magnesium + nitrogen  magnesium nitride

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 3) Calcium chloride and sodium sulfide solutions are mixed. A precipitate of calcium sulfide and sodium chloride solution is made.

? Practice Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each. 3)Calcium chloride and sodium sulfide solutions are mixed. A precipitate of calcium sulfide and sodium chloride solution is made. Calcium chloride + sodium sulfide  calcium sulfide + sodium chloride

? Chemical Equations A chemical equation is a short hand way of representing a chemical change in which chemical formulas are used for the reactants and products.

? States for Substances The states for the substances may be included using the following symbols: State SymbolMeaning (s)Solid (l)liquid (g)gas (aq)aqueous

? Examples H 2 (g) + O 2 (g)  H 2 O (l) C 2 H 2 (g)+ O 2 (g)  CO 2 (g) + H 2 O (l)

? Reminders Don’t forget the diatomic elements: Hydrogen H 2 Fluorine F 2 Oxygen O 2 Chlorine Cl 2 Nitrogen N 2 Bromine Br 2 Iodine I 2 Don’t forget to criss-cross the numbers in the ions to make the subscripts in the compounds.

? Examples Translate the following word equations into chemical equations: 1) sodium + chlorine  sodium chloride

? Examples Translate the following word equations into chemical equations: 1)sodium + chlorine  sodium chloride Na + Cl - diatomic

? Examples Translate the following word equations into chemical equations: 1)sodium + chlorine  sodium chloride Na + Cl - Na + Cl 2  NaCl diatomic

? Examples Translate the following word equations into chemical equations: 2) fluorine + calcium bromide  bromine + calcium fluoride

? Examples Translate the following word equations into chemical equations: 2) fluorine + calcium bromide  bromine + calcium fluoride diatomic

? Examples Translate the following word equations into chemical equations: 2) fluorine + calcium bromide  bromine + calcium fluoride diatomic Ca 2+ Br - Ca 2+ F -

? Examples Translate the following word equations into chemical equations: 2) fluorine + calcium bromide  bromine + calcium fluoride F 2 + CaBr 2  Br 2 + CaF 2 diatomic Ca 2+ Br - Ca 2+ F -

? Examples Translate the following word equations into chemical equations: 3) barium sulfide + potassium iodide  barium iodide + potassium sulfide

? Examples Translate the following word equations into chemical equations: 3) barium sulfide + potassium iodide  barium iodide + potassium sulfide Ba 2+ I - K + I - Ba 2+ S 2- K + S 2-

? Examples Translate the following word equations into chemical equations: 3) barium sulfide + potassium iodide  barium iodide + potassium sulfide BaS + KI  BaI 2 + K 2 S Ba 2+ I - K + I - Ba 2+ S 2- K + S 2-