HESI A2 Chemistry Review Sheet

Comprehensive vocabulary flashcards covering fundamental chemistry topics for the HESI A2 review sheet, including matter, atomic structure, chemical bonds, reactions, acids, bases, and solutions.

Matter

Anything that has mass and takes up space.

Solid

A state of matter characterized by a fixed shape.

Liquid

A state of matter that takes the shape of its container.

Gas

A state of matter that expands to fill its container.

Proton

A subatomic particle located in the nucleus with a positive ($+$) charge.

Neutron

A subatomic particle located in the nucleus with a neutral ($0$) charge.

Electron

A subatomic particle located outside the nucleus with a negative ($-$) charge.

Nucleus (Atomic)

The central core of an atom composed of protons and neutrons.

Atomic Number

The number of protons in an atom (for example, carbon has an atomic number of $6$, meaning it has $6$ protons).

Atomic Mass

Approximately equal to the sum of protons plus neutrons.

Element

A substance that contains only one type of atom (examples include $H$, $O$, $C$, $Na$, and $Cl$).

Compound

A substance composed of two or more elements chemically combined (examples include $H_2O$, $CO_2$, and $NaCl$).

Ionic Bond

A chemical bond in which electrons are transferred; usually occurs between a metal and a nonmetal.

Covalent Bond

A chemical bond in which electrons are shared; usually occurs between a nonmetal and a nonmetal.

Hydrogen Bond

A weak attraction involving hydrogen.

Groups (Periodic Table)

The vertical columns of the periodic table.

Periods (Periodic Table)

The horizontal rows of the periodic table.

Reactants

The starting materials in a chemical reaction that undergo change.

Products

The substances that are produced by a chemical reaction.

Synthesis Reaction

A major reaction type where reactants combine into a product.

Decomposition Reaction

A major reaction type where a compound breaks apart into simpler substances.

Single Replacement Reaction

A reaction type where one element replaces another element in a compound.

Double Replacement Reaction

A reaction type where parts of two compounds switch places.

Acid

A solution with a $pH < 7$ that has more $H^+$ ions.

Neutral Solution

A solution with a $pH = 7$, such as pure water.

Base

A solution with a $pH > 7$ that has more $OH^-$ ions.

pH Scale

A measurement scale from $0$ to $14$ where $0\text{--}6$ is acidic, $7$ is neutral, and $8\text{--}14$ is basic; the lower the $pH$, the stronger the acidity.

Solution

A homogeneous mixture formed by combining a solute and a solvent.

Solute

The component in a solution that gets dissolved (such as salt in saltwater).

Solvent

The component in a solution that does the dissolving (such as water in saltwater).

Concentration

More solute = More concentrated

Less solute = more dilute

Moles

A mole is a counting unit used for particles

Metric Conversions

1 L = 1,000 mL

1 g = 1,000 mg

1 kg = 1,000 g

1 m = 100 cm

1 cm = 10 mm