Chapter 11: Physical and Chemical Changes Vocabulary

Vocabulary flashcards focusing on definitions and core concepts from Chapter 11: Physical and Chemical Changes.

Physical Change

A change in which no new substances are formed, and the change can usually be reversed.

Chemical Change

A change in which one or more new substances are formed through a chemical reaction, and the change is usually not easily reversed.

Reactants

Substances that react with each other in a chemical reaction, positioned on the left-hand side of a word or chemical equation.

Products

The new substances formed in a chemical reaction, positioned on the right-hand side of a word or chemical equation.

Combustion

A chemical reaction in which a substance is heated in the presence of oxygen to form one or more new substances, usually giving out heat and light.

Thermal Decomposition

A reaction in which a substance breaks down into two or more simpler substances upon heating.

Oxidation

A chemical change that occurs when a substance gains oxygen or interacts with oxygen.

Neutralisation

A chemical reaction that occurs when an acid is mixed with an alkali or base to produce a salt and water.

Acid

A substance that dissolves and dissociates in water to produce hydrogen ($H^+$) ions and corresponding negative ions.

Base

A substance, usually a metal oxide or hydroxide, that reacts with an acid to produce a salt and water only.

Alkali

A base that dissolves and dissociates in water to produce hydroxide ($OH^-$) ions and corresponding positive metal ions.

pH Scale

A set of numbers ranging from $0$ to $14$ used to measure how acidic or alkaline a solution is.

Indicators

Substances that change colour depending on whether they are in the presence of an acid or an alkali.

Litmus Paper

An indicator used to test acidity or alkalinity; red litmus paper turns blue in an alkali, and blue litmus paper turns red in an acid.

Salt

A compound formed during an acid reaction that contains a metallic element combined with the negative ion of the acid.

Cation

A positively charged ion formed when a neutral atom loses one or more electrons.

Anion

A negatively charged ion formed when a neutral atom gains one or more electrons.

Law of Conservation of Mass

A fundamental law stating that during a chemical reaction, atoms are neither created nor destroyed; the total number and type of atoms remain conserved.

Polyatomic Ion

An ion composed of two or more covalently bonded atoms that carry an overall positive or negative charge (e.g., $NH_4^+$ or $SO_4^{2-}$).

Acidification of Oceans

The environmental process in which carbon dioxide released into the atmosphere dissolves in seawater to form carbonic acid, decreasing seawater pH and degrading calcium carbonate shells.