Basic Concepts of Chemistry

Definition: Chemistry is the study of matter, its properties, composition, structure, and changes it undergoes during chemical reactions.
Branches:
- Organic Chemistry: Study of carbon-containing compounds.
- Inorganic Chemistry: Study of inorganic compounds.
- Physical Chemistry: Focus on the physical properties and behavior of chemicals.
- Analytical Chemistry: Techniques for analyzing substances.
- Biochemistry: Study of chemical processes within living organisms.

Matter: Anything that has mass and occupies space.
States of Matter:
- Solid: Definite shape and volume.
- Liquid: Definite volume, but no definite shape.
- Gas: No definite shape or volume.
Properties:
- Physical Properties: Can be observed without changing the substance (e.g., color, melting point).
- Chemical Properties: Observed during a reaction (e.g., reactivity, flammability).

Atoms: Basic units of matter made up of protons, neutrons, and electrons.
Subatomic Particles:
- Protons: Positively charged, located in the nucleus.
- Neutrons: Neutral, also in the nucleus.
- Electrons: Negatively charged, orbit around the nucleus.
Atomic Number: Number of protons in the nucleus; defines the element.
Mass Number: Total number of protons and neutrons in the nucleus.

Organization: Elements are arranged by increasing atomic number and grouped by similar properties.
Groups/Families: Vertical columns indicating elements with similar characteristics (e.g., alkali metals, halogens).
Periods: Horizontal rows showing elements with increasing energy levels.

Ionic Bonds: Formed by transfer of electrons from one atom to another, resulting in charged ions.
Covalent Bonds: Formed by sharing pairs of electrons between atoms.
Metallic Bonds: Attraction between metal ions and delocalized electrons.

Types of Reactions:
- Synthesis: Two or more substances combine to form a new compound.
- Decomposition: A single compound breaks down into simpler products.
- Single Replacement: One element replaces another in a compound.
- Double Replacement: Exchange of ions between two compounds.
- Combustion: Reaction with oxygen producing heat and light.

Mole Concept: A mole is a measurement that represents 6.022 x 10²³ entities (Avogadro's number).
Balancing Equations: Ensures mass is conserved during reactions; the number of atoms on reactants side equals the products side.

Acids: Substances that donate protons (H⁺); have a sour taste and turn litmus red.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻); have a bitter taste and turn litmus blue.
pH Scale: Measures acidity or basicity; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

Endothermic Reactions: Absorb energy; feel cold to the touch.
Exothermic Reactions: Release energy; feel hot to the touch.
Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Reaction Rate: Speed at which reactants are converted into products.
Factors Affecting Rate:
- Concentration of reactants.
- Temperature.
- Surface area.
- Presence of a catalyst.

Dynamic Equilibrium: State where the forward and reverse reactions occur at equal rates.
Le Chatelier's Principle: If a change is made to a system at equilibrium, the system will adjust to counteract the change.

This concise overview covers foundational elements of chemistry and can serve as a quick study reference.

The study of matter, its properties, composition, structure and transformations during chemical reactions.

Organic Chemistry: Carbon-containing compounds and their reactions.
Inorganic Chemistry: Compounds that do not contain carbon
Physical Chemistry: Focuses on the physical properties of matter and how energy affects them.
Analytical Chemistry: Methods for analyzing substances and their components.
Biochemistry: Chemical processes in living organisms.

Matter: Anything that has mass and takes up space.
States of Matter:
- Solid: Definite shape and volume.
- Liquid: Definite volume, but takes the shape of its container.
- Gas: No definite shape or volume, expands to fill its container.
Properties:
- Physical properties: can be observed without changing the substance (e.g., color, melting point, boiling point).
- Chemical properties: observed during a chemical reaction (e.g., reactivity, flammability).

Atom: The basic unit of matter, made up of protons, neutrons, and electrons.
Subatomic particles:
- Protons: Positively charged particles found in the nucleus of the atom.
- Neutrons: Neutral particles found in the nucleus of the atom.
- Electrons: Negatively charged particles that orbit the nucleus.
Atomic Number: The number of protons in the nucleus, which defines the element.
Mass Number: The total number of protons and neutrons in the nucleus of an atom.

Organization: Elements are arranged by increasing atomic number in rows and columns.
Groups/Families: Vertical columns on the periodic table. Elements in the same group have similar chemical properties.
Periods: Horizontal rows on the periodic table. Elements in the same period have the same number of electron shells.

Ionic Bond: Formed by the transfer of electrons between atoms.
Covalent Bond: Formed by sharing pairs of electrons between atoms.
Metallic Bond: The attraction between positively charged metal ions and delocalized electrons.

Types of Reactions:
- Synthesis: Two or more substances combine to form one new compound.
- Decomposition: One compound breaks down into two or more simpler products.
- Single Replacement: One element replaces another element in a compound.
- Double Replacement: Two elements in different compounds exchange places.
- Combustion: A substance reacts with oxygen producing heat and light.

Mole: A measurement that refers to a specific quantity of a substance. One mole equals 6.022 x 10²³ particles (Avogadro’s Number ).
Balancing Chemical Equations: Ensures the same number of atoms of each element on the reactants side and the products side of the reaction. Follows the law of conservation of mass.

Acids: Substances that donate protons (H⁺) in solution.
- Characteristics: Taste sour, turns litmus paper red.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻) in solution.
- Characteristics: Taste bitter, turns litmus paper blue.
pH scale: Measures the acidity or alkalinity of a solution. Values range from 0 (most acidic) to 14 (most basic), with 7 being neutral.

Endothermic Reactions: Absorb energy from the surroundings.
Exothermic Reactions: Release energy into the surroundings.
Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed from one form to another.

Reaction Rate: How quickly reactants are transformed into products.
Factors Influencing Reaction Rate:
- Concentration of Reactants: Higher concentrations lead to faster rates.
- Temperature: Increased temperature leads to higher reaction rates (molecules move faster).
- Surface Area: Increased surface area of the reactant allows for more collisions, increasing reaction rate.
- Presence of a Catalyst: A substance that speeds up the rate of a reaction without being consumed itself.

Dynamic Equilibrium: A state where the rates of the forward and reverse reactions are the same.
Le Chatelier’s Principle: If a change is made to a system at equilibrium, the system will shift in a direction to counteract the change.