Chapter 1 - CHEM

Physical change

A change where the identity of a substance does not change, such as a change of state from liquid to gas.

Chemical change

A change that occurs when the identities of substances change and new substances form.

Observations of chemical change

The evolution of a gas, the formation of a precipitate, the release or absorption of energy, and a color change.

Mass

The quantity of matter contained in an object, which remains constant regardless of location.

Weight

The force produced by gravity acting on an object's mass, which can change depending on gravitational pull.

Accuracy

How close a measurement is to the correct or accepted value of the quantity being measured.

Precision

The degree of exactness of a measurement, regardless of its proximity to the true value.

Reactants

The starting substances in a chemical reaction, located on the left-hand side of a reaction arrow.

Products

The new substances made in a chemical reaction, appearing on the right-hand side of the arrow.

Pure substance

A sample of matter with definite chemical and physical properties.

Element

A pure substance that contains only one kind of matter and cannot be broken down by chemical means.

Compound

A pure substance composed of more than one kind of atom, which can be broken down into its elements.

Mixture

A combination of two or more substances that are not chemically combined.

Homogeneous mixture

A mixture with a uniform structure and composition throughout.

Heterogeneous mixture

A mixture composed of dissimilar components with an uneven distribution.

Density

The ratio of an object's mass to its volume, often expressed in g/cm³ or g/mL.

Diatomic

Elements that exist as two atoms of the same element joined together.

Molecule

The smallest unit of a substance that keeps all of the physical and chemical properties of that substance.

Physical property

A characteristic of a substance that does not involve a chemical change.

Chemical property

A property of matter that describes a substance's ability to participate in chemical reactions.

Chemical reaction

The process by which one or more substances change to produce one or more new substances.

States of matter

The physical forms of matter which are solid, liquid, gas, and plasma.

Significant figures

Those digits in a measurement that are known with certainty plus the first digit that is uncertain.

Volume

The space an object occupies.

Solute

The substance which is dissolved in a solution.

Solvent

The substance in which the solute is dissolved.

Solution

A homogeneous mixture that forms a single phase where one substance cannot be differentiated from another.

Conversion factor

A simple ratio that relates two units that express a measurement of the same quantity.

Liquids

Fixed volume but no fixed shape.

Speed of liquid particles

Move faster than solids (medium level speed).

Gas

No fixed shape nor fixed volume.

Movement of gas particles

Move independently at high speed.

Plasma

The fourth state of matter, an ionized gas forming stars and lightning.

Chemical equation reactants

Substances on the left-hand side that are used up.

Chemical equation products

Substances on the right-hand side that are made by the reactants.

Law of conservation of mass

Atoms are not destroyed or created; mass stays the same during a chemical reaction.

Energy transfer signs

A change in temperature or the giving off of light energy.

Color change in reactions

Look for a different color when two chemicals react.