Lab 3: classifying chemical reactions

objective

To perform and observe chemical reactions; to interpret the observations as evidence of a chemical reaction; to write balanced chemical equations for the reactions; to classify each reaction as one of four general types; to learn the proper use of a Bunsen burner

safety

HCl, NaOH, and CuSO4 are caustic, corrosive, irritants, and/or toxic. Heat test tubes using a test tube clamp. Reaction I will produce a flammable gas and must be performed in a separate location from the reactions that involve a Bunsen burner. Reaction VI will produce a gas that is toxic and an irritant. It must be performed in the hood.

evidence of a chemical reaction

• odor

• color change

• formation of a precipitate

• formation of a gas (bubbles)

• change in temp

endothermic

absorb heat from surroundings and feel cold

exothermic

release heat to surroundings and feel hot

synthesis reaction

two substances are combined to form a new compound

decomposition reaction

one compound decomposes into two or more products

displacement reaction

one element replaces another element in a compound

exchange

two ionic compounds switch to form two new ionic compounds

hottest part of oxidizing flame

found at the tip of the inner cone

should be an inch below surface being heated

reaction 1

• Magnesium reacts with HCl in a test tube

• bubbled, hydrogen gas produced

• single displacement reaction

reaction 2

• Copper sulfate is mixed with sodium hydroxide in a test tube

• color change, precipitate formation (Cu(OH)2), cold to touch

• double displacement

reaction 3 & 4

• Copper sulfate pentahydrate is heated to observe changes, then water is added

• Reaction 3: turned white w condensation after heating, decomposition reaction

• Reaction 4: changed back to blue after adding water, synthesis reaction

reaction 5

• Steel wool is placed in copper sulfate solution

• temperature change, wool rusted, solution turned cloudy and brownish

• single displacement reaction

reaction 6

• Ammonium carbonate is heated

• litmus paper turned blue indicating basic

• produced chemical scent (ammonia gas), evaporated, condensation

• thermal decomposition reaction