Introduction to Chemistry

Chemistry is fundamental to understanding matter and its properties.
The periodic table is a critical tool that organizes all known elements, illustrating their relationships and properties.
Understanding elements and compounds is essential for creating new materials and substances.

Elements and Compounds

Elements: The basic building blocks of matter.
- Cannot be broken down further without changing their chemical properties.
- Each element has unique chemical and physical properties that distinguish it from others.
Compounds: A pure substance formed when two or more different elements combine in definite proportions.
- Compounds have properties different from the individual elements that comprise them (e.g., water is distinct from hydrogen and oxygen).

Chemical Properties: Related to the ability of a substance to undergo chemical changes.
- Example: Sodium and chlorine combine chemically to form sodium chloride (table salt), exhibiting different properties than either element alone.
Physical Properties: Observable traits that do not change the substance's identity.
- Examples: Color, state (solid/liquid/gas), and boiling point.
- Altering physical properties, such as cutting hair, does not change the chemical identity of a person.

Organic Chemistry: The study of carbon-containing compounds and their derivatives.
- Focus on hydrocarbons (compounds made of hydrogen and carbon).
Inorganic Chemistry: The study of compounds that do not primarily contain carbon, including acids, bases, and salts.

Matter: Anything that occupies space and has mass.
Atoms: The smallest units of elements, composed of:
- Nucleus: Contains protons (positive charge) and neutrons (neutral charge).
- Electrons: Negatively charged particles that orbit the nucleus; a balanced atom has equal protons and electrons.

Ions: Atoms that have gained or lost electrons, resulting in a charge.
- Example: Sodium (Na) loses an electron to become Na^+; Chloride (Cl) gains an electron to become Cl^−.
Molecules: Formed when two or more atoms bond together.
- Example: Methane (CH₄) consists of one carbon atom and four hydrogen atoms.

Hydrocarbons: Organic compounds consisting solely of hydrogen and carbon.
- Examples of hydrocarbons include:
- Methane (CH₄): 1 carbon, 4 hydrogens.
- Ethane (C₂H₆): 2 carbons, 6 hydrogens.
- Propane (C₃H₈): 3 carbons, 8 hydrogens.
- Continue series up to Decane (C₁₀H₂₂).

Chemical Reactions: The process of combining reactants to form products, involving rearrangement of atoms.
- Reactants: The starting substances that undergo a reaction.
- Products: The substances formed as a result of the reaction.
Catalysts: Substances that accelerate chemical reactions without undergoing any permanent change themselves.

Exothermic Reactions: Produce heat as a byproduct (associated with the term "exo," meaning exit).
Endothermic Reactions: Absorb heat from their surroundings to occur (associated with the term "endo," meaning inside).
- Some reactions may start endothermic and produce heat once initiated, transitioning to an exothermic state.

Mixtures: Combinations of two or more substances that do not combine chemically, such as oil and vinegar.
Solutions: Homogeneous mixtures where one component (the solvent) dissolves another (the solute).
- Example: When Kool-Aid powder is added to water, it creates a solution with properties that differ from both original substances.

pH Scale: Ranges from 0 (highly acidic) to 14 (highly basic); 7 is neutral.
- Example: Coca-Cola has a pH around 2; pure water has a pH of 7.
Acids: Substances that donate protons (H⁺) in a solution.
Bases: Substances that accept protons or produce hydroxide ions (OH⁻) in a solution.
Mixing an acid with a base can neutralize the solution, driving pH towards 7.

Proper Personal Protective Equipment (PPE) should always be used when handling chemicals, especially hazardous ones like sulfuric acid which can cause severe injury.

Chemistry is essential in understanding and manipulating substances for various applications, including industrial processes.