Chemistry Midterm Study Guide

Ozone Layer

Layer of ozone in the stratosphere that absorbs ultraviolet light, protecting Earth’s organisms.

Chemistry

The study of everything around us, including the composition, structure, properties of matter and the changes it undergoes.

Matter

Building blocks of everything in the universe; anything that occupies space and has mass.

Troposphere

The lowest level of the atmosphere made up of the air we breathe.

Stratosphere

The second lowest layer of the atmosphere that contains the protective ozone layer.

Ultraviolet Light

Damages living organisms, including animals and plants.

Ammonia (NH3)

A toxic gas in the form of coolants which escape from refrigerators and harms the ozone layer.

Chlorofluorocarbons (CFCs)

Used as coolants in refrigerators, these are synthetic, stable, and nontoxic compounds made of carbon, fluorine, and chlorine.

Mass

A measurement reflecting the amount of matter; constant and independent of gravity.

Weight

Measure of mass and the force of gravity acting on an object; depends on gravity.

Hypothesis

An educated guess based on observations, typically beginning with "If".

Scientific Method

A systematic process involving repeated steps to support or discard a hypothesis.

Quantitative Data

Data involving numbers followed by their units.

Qualitative Data

Data involving physical characteristics, such as color and shape.

Independent Variable

The variable in an experiment that is manipulated and affects the dependent variable.

Dependent Variable

The variable in an experiment that is measured and may change in response to the independent variable.

Constant

Materials in an experiment that remain unchanged throughout the experiment.

Significant Figures

The digits reported in an answer, reflecting the precision of the measurement.

Accuracy

How close a measured value is to an accepted value or the true value.

Precision

How close a series of measurements are to one another.

Density

A physical property measuring mass per unit volume; derived unit is g/cm3.

Atomic Number

The number of protons in an atom; it defines the element.

Ion

A positively or negatively charged atom caused by the loss or gain of electrons.

Cation

A positively charged ion, formed by the loss of electrons.

Anion

A negatively charged ion, formed by the gain of electrons.

Isotope

Atoms of the same element with different numbers of neutrons, resulting in different atomic masses.

Radioisotope

Isotopes with unstable nuclei that release radiation and are radioactive.

Electromagnetic Radiation

A form of energy exhibiting wave-like behavior as it travels through space.

Wavelength

The distance between a point on a wave and the nearest point just like it.

Frequency

The number of wavelengths that pass a fixed point each second.

Planck’s Constant

6.626 x 10^-34 J x s, a constant used to calculate the energy of photons.

Noble Gas Configuration

A shorter way to represent the electron configuration of an element using the nearest noble gas.

Periodic Table

A chart organizing elements by increasing atomic number and similar properties.

Law of Conservation of Mass

States that mass is neither created nor destroyed in chemical reactions.

Dalton’s Atomic Theory

Proposes that matter is composed of atoms that are indivisible and indestructible.