Chemistry Midterm

Atomic Number

The number of protons in an atom, which defines the element.

Mole (mol)

A unit of measurement for amount of substance, it is defined as exactly 6.022 x 10^23 particles.

Significant Figures

The digits in a number that carry meaningful information about its precision.

Hypothesis

An educated guess based on observations that can be tested through experimentation.

Independent Variable

The variable that is manipulated or changed in an experiment.

Dependent Variable

The variable that is measured and affected during the experiment.

Precision

The consistency of repeated measurements or how close they are to each other.

Accuracy

How close a measurement is to the true or accepted value.

Covalent Bonds

A type of chemical bond where two atoms share one or more pairs of valence electrons.

Halogens

Group of elements in Group 17 that are highly reactive and have seven valence electrons.

Noble Gases

Group of elements in Group 18 that are colorless, odorless, and inert due to having a full valence shell.

Kilogram (kg)

The SI base unit of mass, equal to 1000 grams.

Millimeter (mm)

A metric unit of length equal to one thousandth of a meter.

Periodic Table

A tabular arrangement of elements based on increasing atomic number and recurring chemical properties.

Mixture

A combination of two or more substances in which each substance retains its individual properties.

Atom

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

Chemical Change

A process that involves one or more substances changing into new substances, resulting in changes in properties.

Physical Change

A change that affects one or more physical properties of a substance without altering its chemical composition.

Density Formula

Density is calculated using the formula Density = Mass/Volume.

Kinetic Energy

The energy of motion; for an object, it is calculated as KE = ½ mv².

Observations

Data collected through the senses or instrumentation during an experiment.

Electron Affinity

The amount of energy released when an electron is added to a neutral atom in the gaseous phase.

Electronegativity

A measure of how strongly an atom attracts electrons in a chemical bond.

Stoichiometry

The calculation of reactants and products in chemical reactions, based on the conservation of mass.