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1.1 Matter and Its Properties
1.1.1 Definition of Matter
Matter occupies space and possesses mass. Mass is an intrinsic property of matter. Weight is the force, due to gravity, with which an object is attracted to the earth. Force and mass are related to each other by Newton’s equation (Newton’s Law), F ma, where F force, m mass, and a acceleration. Weight and mass are related by the equation w mg, where w weight, m mass, and g acceleration due to gravity. Note that the terms “mass” and “weight” are often (incorrectly) used interchangeably in most literature.
1.1.2 States of Matter
Matter occurs in three states or phases: solid, liquid, and gas. A solid has both a definite size and shape. A liquid has a definite volume but takes the shape of the container, and a gas has neither definite shape nor definite volume.
1.1.3 Composition of Matter
Matter is divided into two categories: distinct substances and mixtures. Distinct substances are either elements or compounds. An element is made up of only one kind of atom. A compound is composed of two or more kinds of atoms joined together in a definite composition.
Mixtures contain two or more distinct substances more or less intimately jumbled together. A mixture has no unique set of properties: it possesses the properties of the substances of which it is composed.
In a homogeneous mixture, the composition and physical properties are uniform throughout. Only a single phase is present. A homogeneous mixture can be gaseous, liquid, or solid. A heterogeneous mixture, such as oil and water, is not uniform and consists of two or more phases.
1.1.4 Properties of Matter
Extensive properties, such as mass and volume, depend on the size of the sample. Intensive properties, such as melting point, boiling point, and density, are independent of sample size. Physical properties of matter are those properties that can be observed, usually with our senses. Examples of physical properties are physical state, color, and melting point.
Chemical properties of a substance are observed only in chemical reactions involving that substance. Reactivity is a chemical property that refers to the tendency of a substance to undergo a particular chemical reaction.
Conservation of Matter
Chemical changes are those that involve the breaking and/or forming of chemical bonds, as in a chemical reaction. Physical changes do not result in the formation of new substances. Changes in state are physical changes.