Signs of a Chemical Reaction

Color Change A change in color is also another characteristic of a chemical reaction taking place. However; sometimes a change in color is simply the mixing of two colors, but no real change in the composition of the substances in question.

Precipitate Forms The formation of a precipitate may be one of the most common signs of a chemical reaction taking place. A precipitate is defined to be a solid that forms inside of a solution or another solid.

Energy Change A chemical reaction involves the breaking of bonds in the reactants and the forming of bonds in the products. It takes energy to break bonds. Energy is released when bonds are formed.

Gas Forms The formation of bubbles (gas) is an indicator of a chemical reaction taking place. When bubbles form, a temperature change could also be taking place. Temperature change and formation of bubbles often occur together.

Change in Properties Pick a property that uniquely characterizes one of the compounds involved in the suspected reaction, and monitor it. If the property really distinguishes that compound from all the others, you'll see it change when a reaction occurs.

Identification Practice MLA heading Title: Identification Practice Number 1-10, skip 3 lines in between For each slide: List the chemical combination Identify each reaction as a chemical reaction or a physical change List your observations that support your inference

1. zinc + hydrochloric acid

2. iron + copper (II) sulfate

3. When a strip of magnesium metal is heated in oxygen, it bursts into an intensely white flame and produces a finely powdered dust of magnesium oxide.

4. sodium carbonate + calcium chloride

5. A blacksmith heats solid iron until it glows bright orange 5. A blacksmith heats solid iron until it glows bright orange. He removes it from the heat and immediately begins to shape it using an anvil.

6. potassium chloride + sodium carbonate

7. If ordinary table sugar (sucrose, C12H22O11) is heated strongly in pure oxygen (O2), it will ignite and burn, producing carbon dioxide and water vapor.

8. potassium hydrogen carbonate + hydrochloric acid

9. A student takes one beaker containing 40mL of pure water, a second beaker containing 40mL of 20 percent salt water. Each system is heated the same way. The beaker containing the salt water will come to a boil first.

10. copper + hydrochloric acid