Basic Concepts in Chemistry

Matter: Anything that has mass and occupies space. Classified into:
- Elements: Pure substances made of one type of atom (e.g., hydrogen, oxygen).
- Compounds: Substances made of two or more elements chemically bonded (e.g., water, H2O).
- Mixtures: Combinations of two or more substances that retain their individual properties (e.g., air, salad).
Atomic Structure:
- Atoms: Basic unit of matter, composed of:
  - Protons: Positively charged particles found in the nucleus.
  - Neutrons: Neutral particles also in the nucleus.
  - Electrons: Negatively charged particles orbiting the nucleus.
- Atomic Number: Number of protons in an atom; defines the element.
- Mass Number: Total number of protons and neutrons.
Chemical Bonds:
- Ionic Bonds: Formed through the transfer of electrons between atoms (e.g., NaCl).
- Covalent Bonds: Formed through the sharing of electrons (e.g., H2O).
- Metallic Bonds: Between metal atoms, involving delocalized electrons.

Solid: Definite shape and volume; particles are closely packed.
Liquid: Definite volume but takes the shape of the container; particles are close but can move.
Gas: No definite shape or volume; particles are far apart and move freely.
Plasma: Ionized gas with free electrons, found in stars.

Reactants: Substances that undergo change in a reaction.
Products: New substances formed as a result of a chemical reaction.
Types of Reactions:
- Synthesis: Combining substances to form a compound (A + B → AB).
- Decomposition: Breaking down a compound into simpler substances (AB → A + B).
- Single Replacement: One element replaces another in a compound (A + BC → AC + B).
- Double Replacement: Exchange of ions between two compounds (AB + CD → AD + CB).
- Combustion: Reaction with oxygen, producing heat and light (typically burning hydrocarbons).

Organization: Arranged by increasing atomic number; columns are groups with similar properties.
Groups: Vertical columns (e.g., alkali metals, alkaline earth metals, halogens, noble gases).
Periods: Horizontal rows representing energy levels.

Acids: Substances that donate protons (H+) in solution; tastes sour, turns litmus red.
Bases: Substances that accept protons or donate hydroxide ions (OH-); tastes bitter, turns litmus blue.
pH Scale: Measures acidity or basicity; ranges from 0 (strong acid) to 14 (strong base), with 7 being neutral.

Mole: Unit measuring amount of substance; 1 mole = 6.022 x 10²³ particles (Avogadro's number).
Balancing Reactions: Ensures the law of conservation of mass; same number of each type of atom on both sides of the equation.

Endothermic Reactions: Absorb heat from the surroundings (e.g., melting ice).
Exothermic Reactions: Release heat to the surroundings (e.g., combustion of fuels).
Enthalpy (ΔH): Measure of heat content in a system.

Hydrocarbons: Compounds composed of carbon and hydrogen (e.g., methane, ethylene).
Functional Groups: Specific groups of atoms that determine the characteristics of organic compounds (e.g., alcohols, amines, carboxylic acids).

Personal Protective Equipment (PPE): Always wear goggles, gloves, and lab coats.
Chemical Handling: Know the properties of chemicals being used; follow all safety protocols.
Waste Disposal: Dispose of chemicals as per local regulations; do not pour down the drain without permission.

Matter includes anything with mass and volume, divided into elements, compounds, and mixtures.
Elements are pure substances with one type of atom (e.g., hydrogen, oxygen).
Compounds consist of two or more elements chemically bonded (e.g., water, H2O).
Mixtures maintain individual properties while combining two or more substances (e.g., air, salad).
Atoms are the fundamental units of matter, containing protons, neutrons, and electrons.
Protons are positively charged particles located in the nucleus; neutrons are neutral and also found there.
Electrons are negatively charged and orbit the nucleus.
Atomic number indicates the number of protons and defines the element; mass number is the sum of protons and neutrons.
Chemical bonds include ionic bonds (electron transfer), covalent bonds (electron sharing), and metallic bonds (delocalized electrons among metal atoms).

Solids have a definite shape and volume with closely packed particles.
Liquids have a definite volume but take the shape of their container; particles are close yet mobile.
Gases lack definite shape and volume with widely spaced particles that move freely.
Plasma consists of ionized gas with free electrons, commonly found in stars.

Reactants are the starting substances in a chemical reaction, while products are the new substances formed.
Synthesis reactions create compounds from simpler substances (e.g., A + B → AB).
Decomposition reactions break down compounds into simpler substances (e.g., AB → A + B).
Single replacement reactions involve one element replacing another in a compound (e.g., A + BC → AC + B).
Double replacement reactions exchange ions between two compounds (e.g., AB + CD → AD + CB).
Combustion reactions involve oxygen and typically produce heat and light from burning hydrocarbons.

The periodic table is organized by increasing atomic number, with vertical columns (groups) showing similar properties.
Groups include categories such as alkali metals, alkaline earth metals, halogens, and noble gases.
Periods represent the energy levels and are arranged horizontally.

Acids donate protons (H+) and have a sour taste; they turn litmus paper red.
Bases accept protons or donate hydroxide ions (OH-) and have a bitter taste; they turn litmus paper blue.
The pH scale ranges from 0 (strong acid) to 14 (strong base), with 7 as neutral.

A mole quantifies the amount of substance, equating to 6.022 x 10²³ particles (Avogadro's number).
Balancing reactions is essential for adhering to the law of conservation of mass, ensuring the same atom count on both reaction sides.

Endothermic reactions absorb heat from their surroundings (e.g., melting ice).
Exothermic reactions release heat into the environment (e.g., combustion of fuels).
Enthalpy (ΔH) measures heat content within a chemical system.

Hydrocarbons are compounds formed from carbon and hydrogen (e.g., methane, ethylene).
Functional groups are specific atom arrangements that define the properties of organic compounds (e.g., alcohols, amines, carboxylic acids).

Personal Protective Equipment (PPE) should include goggles, gloves, and lab coats.
Understand chemical properties before handling and always follow safety protocols.
Dispose of chemicals properly according to local regulations; avoid pouring down the drain without permission.