Chem (exam)

Pure Substance

A classification of matter characterized by an unchanging or specific composition.

Element

The simplest type of matter that is composed of only one type of atom.

Compound

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

Heterogeneous Mixture

A mixture with components that can be physically identified or distinguished because the parts are not evenly distributed in the sample.

Homogeneous Mixture

A mixture that exists in a single phase, with uniform appearance and the same properties and composition throughout the sample.

Solution

A homogeneous mixture of two or more substances in different combinations.

Solute

The substance that gets dissolved in a solution.

Solvent

The dispersing medium in a solution that does the dissolving.

Atom

The smallest unit of an element that retains the chemical properties of that element.

Solid

A state of matter defined by a definite shape and volume, with tightly packed particles that vibrate in a fixed position.

Liquid

A state of matter with no definite shape but a definite volume, where particles can move past each other and flow freely.

Gas

A state of matter that takes the shape and volume of its container, with particles that are far apart and easily compressed.

Plasma

The fourth state of matter, made up of groups of negatively and positively charged particles.

Bose-Einstein Condensate (BEC)

A state of matter in which a cloud of bosons is cooled to temperatures very close to absolute zero.

Physical Property

A property of matter that can be observed without changing the composition of a substance.

Chemical Property

A characteristic of matter that can be observed with an accompanying change in the chemical composition of a substance.

Extensive Property

Properties such as mass, length, size, and volume that depend on the amount of matter.

Intensive Property

A characteristic of matter that can sometimes be used to distinguish a specific substance from all other substances.

Filtration

The process whereby fluids pass through a filter or a filtering medium.

Centrifugation

A method of separating mixtures by rotating containers of liquids to separate suspended materials with different densities.

Decantation

A method of separating mixtures by allowing a heavy insoluble solid to settle to the bottom of a container, and carefully pouring off the liquid above the solid into another container.

Evaporation

The process of changing state from a liquid to a gas, occurring only from the surface of the liquid.

Distillation

A method used to separate a liquid from a solution through boiling and condensation.

Chromatography

A method used to separate small amounts of chemicals so that they can be analyzed, where different substances or components move at different speeds through a strip of wet paper.

Scientific Notation

A simple way to write and keep track of very large or very small numbers without having to deal with a lot of zeros.

Accuracy

A measure of how close a measurement is to the true or accepted value.

Precision

The closeness of measurements within a set of data to one another.

Significant Figures

The certain digits and the estimated digit of a measurement, used to determine the level of precision in a measurement.

Triple Beam Balance

A weighing balance accurate to one decimal place.

Top Loading Balance

A weighing balance accurate up to two decimal places.

Analytical Balance

A weighing balance accurate up to four decimal places.

Volume

The amount of space occupied by an object.

Meniscus

The curved interface of a liquid in any container, observed to measure a liquid's volume.

Density

The mass per unit volume of a material.

Displacement method

A method of measuring the volume of an irregularly shaped object.

Law of Conservation of Mass

The law stating that mass is neither created nor destroyed in a chemical reaction.

Law of Definite Proportions

The law stating that any sample of a given compound will always be composed of the same elements in the same proportions by mass.

Law of Multiple Proportions

The law stating that for elements that can form different compounds between them, the masses of the second element that can combine with a fixed mass of the first element are in ratio of small whole numbers.

Atomic Theory

The theory proposed by John Dalton stating that matter is made of extremely small indivisible particles called atoms.

Cathode rays

Rays observed in an evacuated tube that can be deflected by a magnetic field, leading to the discovery of electrons by J.J. Thomson.

Plum-pudding model

A model proposed by J.J. Thomson for the atom, where electrons are embedded in a positively charged "pudding" of matter.

Nucleus

The central part of an atom, discovered by Ernest Rutherford, consisting of protons and neutrons.

Proton

A subatomic particle with a positive charge found in the nucleus of an atom.

Neutron

A subatomic particle with no charge found in the nucleus of an atom.

Isotopes

Atoms of the same element with different numbers of neutrons.

Ion

An electrically charged particle formed when a neutral atom gains or loses one or more electrons.

Cation

A positively charged ion formed when a metal loses electrons.

Anion

A negatively charged ion formed when a nonmetal gains electrons.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, converting carbon dioxide and water into glucose and oxygen.