Recognizing Chemical Reactions

Vocabulary flashcards focusing on key terms, definitions, and visual indicators of chemical reactions.

Visual Clues of a Chemical Reaction

The four observable indicators that a chemical reaction is likely occurring: a change in color, production of a gas, formation of a precipitate, and a transfer of energy.

Precipitate

A solid product that forms from a chemical reaction and settles out of a liquid solution.

Mercury (II) oxide

A red solid reactant that decomposes upon heating into silver liquid mercury metal and oxygen gas.

Mercury metal

A silver liquid element formed, along with oxygen gas, when red mercury (II) oxide is heated.

Zinc and Hydrochloric Acid Reaction

A chemical reaction that bubbles vigorously as hydrogen gas is produced and releases energy, causing the container to become warm.

Lead (II) iodide Precipitate

A yellow solid precipitate formed instantly when a colorless solution of lead (II) nitrate is mixed with a colorless solution of potassium iodide.

Composition Testing

The only certain method to confirm a chemical reaction has occurred by verifying that the composition of the final substances is different from the starting materials.

Energy Transfer in Physical Changes

Energy transfers that occur without changing chemical composition, such as energy absorption during melting or energy release during condensation.

Pizza Cooking Indicators

Observable signs that cooking is occurring, such as the crust turning light brown, dough becoming rigid, and cheese melting.