Basic Concepts of Chemistry

Basic Concepts of Chemistry

• Matter: Anything that has mass and takes up space.
• Element: A pure substance that cannot be broken down into simpler substances. Examples: Hydrogen (H), Oxygen (O).
• Compound: A substance formed when two or more elements chemically bond together. Example: Water (H₂O).
• Mixture: A combination of two or more substances that are not chemically bonded.

States of Matter

1. Solid: Fixed shape and volume; particles tightly packed.
2. Liquid: Fixed volume but no fixed shape; particles are close but can flow.
3. Gas: No fixed shape or volume; particles are far apart and move freely.

Chemical Bonding

• Ionic Bonds: Formed by the transfer of electrons from one atom to another; results in oppositely charged ions.
• Covalent Bonds: Formed by the sharing of electrons between atoms.
• Metallic Bonds: Involves the pooling of electrons among metal atoms.

Chemical Reactions

• Reactants: Substances that undergo a change during a chemical reaction.
• Products: Substances formed as a result of a chemical reaction.
• Types of Reactions:
  • Synthesis: Two or more reactants combine to form a single product.
  • Decomposition: A single compound breaks down into two or more products.
  • Single Replacement: One element replaces another in a compound.
  • Double Replacement: Exchange of ions between two compounds.

The Periodic Table

• Groups (Columns): Elements in the same group have similar chemical properties. Example: Group 1 (Alkali Metals).
• Periods (Rows): Elements in the same period have the same number of electron shells.
• Metals, Nonmetals, Metalloids: Distinct categories based on physical and chemical properties.

Acids and Bases

• Acids: Substances that donate protons (H⁺) and produce hydronium ions (H₃O⁺) in solutions. Example: Hydrochloric acid (HCl).
• Bases: Substances that accept protons or produce hydroxide ions (OH⁻). Example: Sodium hydroxide (NaOH).
• pH Scale: Measures the acidity or basicity of a solution (0-14 range; <7 is acidic, >7 is basic).

Stoichiometry

• Mole: A unit that measures the amount of substance (6.022 x 10²³ particles).
• Molar Mass: The mass of one mole of a substance.
• Balanced Reactions: In chemical equations, the number of atoms must be the same on both sides.

Thermodynamics in Chemistry

• Exothermic Reactions: Release energy (usually as heat) into the surroundings.
• Endothermic Reactions: Absorb energy from the surroundings.
• Enthalpy (ΔH): A measure of heat content during a reaction.

Key Concepts of Organic Chemistry

• Hydrocarbons: Compounds composed only of hydrogen and carbon. Types include:
  • Alkanes: Single bonds (saturated).
  • Alkenes: At least one double bond.
  • Alkynes: At least one triple bond.
• Functional Groups: Specific groups of atoms within molecules that determine the characteristics and chemical reactivity of the compounds. Examples: Hydroxyl (-OH), Carboxyl (-COOH).

Matter and Its Composition

• Anything that has mass and takes up space is considered matter.
• Elements are pure substances that cannot be broken down further. Examples include hydrogen (H) and oxygen (O).
• Compounds are formed when two or more elements chemically bond together, like water (H₂O).
• Mixtures are combinations of substances that are not chemically bonded.

States of Matter

• Solids have a fixed shape and volume with particles tightly packed.
• Liquids maintain a fixed volume but lack a fixed shape, with particles close together and able to flow.
• Gases have no fixed shape or volume, with particles far apart and moving freely.

Chemical Bonding

• Ionic bonds occur when electrons are transferred between atoms, resulting in oppositely charged ions.
• Covalent bonds involve the sharing of electrons between atoms.
• Metallic bonds occur when electrons are pooled between metal atoms.

Chemical Reactions

• Reactants are substances that undergo a change during a chemical reaction.
• Products are substances formed as a result of a chemical reaction.
• Synthesis reactions combine two or more reactants to form a single product.
• Decomposition reactions break down a single compound into two or more products.
• Single replacement reactions involve one element replacing another in a compound.
• Double replacement reactions exchange ions between two compounds.

The Periodic Table

• Groups (columns) on the periodic table contain elements with similar chemical properties. For example, Group 1 contains the Alkali Metals.
• Periods (rows) on the periodic table represent elements with the same number of electron shells.
• Elements are classified as metals, nonmetals, or metalloids based on their physical and chemical properties.

Acids and Bases

• Acids donate protons (H⁺) and produce hydronium ions (H₃O⁺) in solutions. An example is hydrochloric acid (HCl).
• Bases accept protons or produce hydroxide ions (OH⁻). Sodium hydroxide (NaOH) is an example.
• The pH scale measures acidity or basicity of a solution, ranging from 0 to 14, with 7 being neutral.

Stoichiometry

• The mole is a unit that measures the amount of substance, equivalent to 6.022 x 10²³ particles.
• Molar mass represents the mass of one mole of a substance.
• Balanced chemical equations ensure that the number of atoms of each element is the same on both sides of the reaction.

Thermodynamics in Chemistry

• Exothermic reactions release energy (often as heat) into their surroundings.
• Endothermic reactions absorb energy from their surroundings.
• Enthalpy (ΔH) measures the heat content change during a reaction.

Key Concepts of Organic Chemistry

• Hydrocarbons are compounds composed solely of hydrogen and carbon.
• Alkanes contain only single bonds and are considered saturated.
• Alkenes have at least one double bond.
• Alkynes have at least one triple bond.
• Functional groups are specific groups of atoms within molecules that determine the characteristics and chemical reactivity of compounds. Examples include the hydroxyl group (-OH) and carboxyl group (-COOH).