Ch 1 Textbook Terms

Conversion factor

A fraction whose numerator and denominator are the same quantity expressed in different units.

Law of constant composition

A law that states that the elemental composition of a compound is always the same; also called the law of definite proportions.

Precision

The closeness of agreement among several measurements of the same quantity.

Law of definite proportions

A law that states that the elemental composition of a substance is always the same; also called the law of constant composition.

Energy

The capacity to do work or to transfer heat.

Celsius scale

A temperature scale on which water freezes at 0° and boils at 100° at sea level.

Changes of state

Physical changes of matter from one state to a different one, for example, from a gas to a liquid.

Kelvin scale

The SI temperature scale; the SI unit for temperature is the kelvin. Zero on the Kelvin scale corresponds to -273.15 °C.

Mixtures

A combination of two or more substances in which each substance retains its own chemical identity.

Property

Any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types.

Accuracy

A measure of how closely individual measurements agree with the correct, or “true,” value.

Kinetic energy

The energy that an object possesses by virtue of its motion.

Scientific law

A statement of what is always observed to happen, to the best of our knowledge.

Chemical change

Processes in which a substance is transformed into a chemically different substance; also called chemical reactions.

Theory

A tested model or explanation that has predictive powers and that accounts for all available observations.

Elements

A substance that cannot be decomposed into simpler substances.

Solid

Matter that has both a definite shape and a definite volume.

Temperature

A measure of the hotness or coldness of an object; a physical property that determines the direction of heat flow.

Extensive properties

A property that depends on the amount of sample considered; for example, mass or volume.

Chemical properties

Properties that describe the way a substance may change, or react, to form other substances.

Physical properties

Properties that can be measured without changing the composition of a substance, for example, color and freezing point.

Chemistry

The scientific discipline that studies matter, its properties, and the changes that matter undergoes.

Heat

The energy that causes the temperature of an object to increase. The flow of energy from a body at higher temperature to one at lower temperature when they are placed in thermal contact.

States of matter

The three forms that matter can assume

Matter

Anything that occupies space and has mass; the physical material of the universe.

Intensive properties

A property that does not depend on the amount of sample being examined, for example, density.

Solutions

A mixture of substances that has a uniform composition; a homogeneous mixture.

Liquid

Matter that has a distinct volume independent of its container.

Calorie

A unit of energy; it is the amount of energy needed to raise the temperature of 1 g of water by 1 °C from 14.5 °C to 15.5 °C. A related unit is the joule

Pure substance

Matter that has a fixed composition and distinct properties.

Mass

A measure of the amount of material in an object. In SI units, mass is measured in kilograms.

Chemical reaction

Processes in which a substance is transformed into a chemically different substance; also called chemical changes.

Absolute zero

The temperature at which all thermal motion ceases

Metric system

A system of measurement used in science and in most countries. The meter and the gram are examples of metric units.

Molecule

A chemical combination of two or more atoms.

Density

The amount of mass in a unit volume of a substance.

Compounds

A substance composed of two or more elements united chemically in definite proportions.

Dimensional analysis

A method of problem solving in which units are multiplied together or divided into each other along with the numerical values. It ensures that the final answer of a calculation has the desired units.

Physical change

Changes in physical appearance (such as a phase change) that occur with no change in chemical composition.

Scientific method

The general process of advancing scientific knowledge by making experimental observations and by formulating hypotheses, theories, and laws.

SI units

The preferred metric units for use in science.

Work

The energy transferred when a force exerted on an object causes a displacement of that object.

Atoms

The smallest representative particle of an element. The almost infinitesimally small building blocks of matter.

Distillation

A separation process that depends on the different boiling points of substances.

Derived unit

An SI unit obtained by multiplication or division of one or more of the SI base units.

Potential energy

The energy that an object possesses as a result of its position with respect to another object.

Significant figures

The digits that indicate the precision with which a measurement is made; all digits of a measured quantity are significant, including the last digit, which is uncertain.

Gas

Matter that has no fixed volume or shape; it uniformly fills its container.

Force

A push or a pull.