Chemistry Overview and Matter Classifications

Chemistry Overview

• Chemistry studies matter, including its composition, properties, structures, and transformations.
• Matter is anything that occupies space and has mass.
• Mass quantifies matter in an object; weight measures the gravitational pull on that mass.

Classifications of Matter

• Matter is classified into two categories: pure substances and mixtures.

Pure Substances

• Elements:

  • Comprise single atoms, cannot be simplified further.
  • Unique properties; 118 known elements, with 92 occurring naturally.
  • Represented by symbols (1 or 2 letters, first letter capitalized).

• Compounds:

  • Composed of elements in fixed ratios; original properties of elements are lost.
  • Cannot be separated through physical methods, only chemical processes.
  • Examples include:
    • Carbon Dioxide (CO2)
    • Magnesium Hydroxide (Mg(OH)2)
    • Sucrose (C12H22O11)
    • Hydrochloric Acid (HCl)

Types of Elements

• Metals:

  • Most are solid at room temperature (except Hg).
  • Good conductors of heat and electricity; malleable and ductile.

• Non-metals:

  • Poor conductors; not malleable or ductile.

• Metalloids:

  • Exhibit properties of both metals and non-metals.
  • Also known as semiconductors; conduct electricity better than non-metals but worse than metals.

Kinds of Compounds

• Salts: Formed from a metal and a non-metal (e.g., MgCl2, KF).
• Acids: Combinations of hydrogen ions (H+) with non-metals or polyatomic ions (e.g., HCl, H2SO4).
• Bases: Comprise metals and hydroxide ions (OH-) (e.g., NaOH, Mg(OH)2).
• Organic Compounds: Mainly hydrocarbons (e.g., CH4, C2H6).

Mixtures

• Combinations of elements or compounds where individual properties remain.
• Can be separated by physical methods.

Types of Mixtures

• Homogeneous Mixtures:

  • Uniform composition; constituents are indistinguishable (e.g., milk, soy sauce).

• Heterogeneous Mixtures:

  • Non-uniform composition; different components can be identified (e.g., oil and water, salad).

Properties of Matter

• Physical Properties:

  • Observable characteristics (e.g., color, smell, mass, temperature).

• Chemical Properties:

  • Characteristics that lead to new product formation (e.g., flammability, oxidation).

Changes in Matter

• Physical Changes:

  • Alterations in physical attributes without changing composition (e.g., melting ice).

• Chemical Changes:

  • Result in the formation of new substances (e.g., burning wood).

Types of Physical Properties

• Intensive Properties:

  • Independent of the amount of substance (e.g., color, boiling point).

• Extensive Properties:

  • Dependent on the amount of substance (e.g., mass, volume).

Phases of Matter

• Solid:

  • Molecules tightly packed; has a fixed volume.

• Liquid:

  • Molecules are less dense; flows easily.

• Gas:

  • Molecules are widely spaced; fills the container.

Laws of Matter

• Law of Conservation of Mass:
  • Mass is neither created nor destroyed in a chemical reaction; total mass of reactants equals total mass of products.