Introduction to Chemistry

• Chemistry is the study of matter and its properties, as well as how matter changes.
• Matter is anything that has mass and takes up space.
• Chemistry is concerned with atoms and their interactions with other atoms.

Basic Concepts

• An atom is the smallest unit of an element that retains the chemical properties of that element.
• Elements are substances that cannot be broken down into simpler substances by chemical means; elements are defined by the number of protons they possess.
• A compound is a substance composed of two or more elements chemically combined in a fixed ratio.
• A molecule is the smallest particle of a compound that retains the chemical properties of that compound.
• Chemical bonds are the attractive forces that hold atoms together in molecules and compounds.
• Chemical reactions involve the rearrangement of atoms and molecules to form new substances

States of Matter

• Solid: Has a definite shape and volume; particles are tightly packed.
• Liquid: Has a definite volume but takes the shape of its container; particles are close but can move around.
• Gas: Has no definite shape or volume; particles are widely separated and move freely.
• Plasma: An ionized gas at high temperature.

Chemical Reactions

• Reactants are the starting materials in a chemical reaction.
• Products are the substances formed as a result of a chemical reaction.
• A chemical equation represents a chemical reaction using chemical formulas and symbols.
• Balancing chemical equations ensures that the number of atoms of each element is the same on both sides of the equation, following the law of conservation of mass.

Chemical Equations

• A chemical equation is a symbolic representation of a chemical reaction.
• Reactants are written on the left side of the arrow, and products are written on the right side.
• Coefficients are used to balance the equation, ensuring the number of atoms for each element is the same on both sides.
• States of matter are often indicated in parentheses: (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solution.

The Mole

• Represents a specific number of particles (atoms, molecules, ions, etc.)
• One mole is defined as containing exactly 6.02214076 × 10^23 elementary entities.
• The number is known as Avogadro's number (NA).
• Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).
• The molar mass of an element is numerically equal to its atomic mass in atomic mass units (amu).

Solutions

• A solution is a homogeneous mixture of two or more substances.
• The solute is the substance being dissolved, and the solvent is the substance doing the dissolving.
• Concentration is the amount of solute present in a given amount of solvent or solution.
• Molarity (M) is a common unit of concentration, defined as the number of moles of solute per liter of solution (mol/L).
• Molality (m) is defined as the number of moles of solute per kilogram of solvent (mol/kg).

Acids and Bases

• Acids are substances that produce hydrogen ions (H+) when dissolved in water.
• Bases are substances that produce hydroxide ions (OH-) when dissolved in water.
• The pH scale measures the acidity or basicity of a solution.
• pH ranges from 0 to 14, with 7 being neutral, values less than 7 being acidic, and values greater than 7 being basic.
• Strong acids and bases completely dissociate in water, while weak acids and bases only partially dissociate.
• Neutralization occurs when an acid and a base react to form a salt and water.

Organic Chemistry

• Focuses on compounds containing carbon.
• Carbon can form four covalent bonds, allowing for a wide variety of complex structures.
• Hydrocarbons are compounds containing only carbon and hydrogen.
• Alkanes, alkenes, and alkynes are examples of hydrocarbons with single, double, and triple bonds, respectively.
• Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.