Matter and Its Properties

Posted on Oct 13, 2024 in Chemistry

Mixtures

A mixture is a substance formed by combining two or more substances that do not react chemically. Mixtures can be separated by physical processes, and their composition and properties are variable.

Types of Mixtures:

  • Homogeneous: The components are not distinguishable.
  • Heterogeneous: The various components are observable.

Pure Substances

A pure substance cannot be separated into simpler substances through physical processes. Its composition and physical properties are constant.

Types of Pure Substances:

  • Elements: Cannot be decomposed into simpler substances by chemical processes.
  • Compounds: Can be broken down into simpler substances through chemical processes.

Properties of Matter

Physical Properties:

Characteristics of matter that can be observed without changing its composition (e.g., hardness, solubility).

Chemical Properties:

Characteristics of matter that describe how it changes its composition (e.g., combustion).

Extensive Properties:

Properties that depend on the amount of matter present (e.g., volume).

Intensive Properties:

Properties that do not depend on the amount of matter present (e.g., melting point).

Chemical Reactions

A chemical reaction is a process in which one or more substances, called reactants, are transformed into different substances, called products.

Laws of Chemical Reactions:

  • Lavoisier’s Law (Conservation of Mass): The total mass of reactants equals the total mass of products in a chemical reaction.
  • Proust’s Law (Law of Definite Proportions): The ratio of the masses of elements in a compound is always constant.
  • Dalton’s Law (Law of Multiple Proportions): If two elements form more than one compound, the masses of one element combine with a fixed mass of the other in simple whole-number ratios.

Dalton’s Atomic Theory

  • Elements consist of indivisible and indestructible atoms.
  • Atoms of the same element are identical in mass and properties.
  • Atoms of different elements have different masses and properties.
  • Compounds are formed by combining atoms of different elements in simple whole-number ratios.
  • Molecules are identical in mass and properties.

Gas Laws

  • Gay-Lussac’s Law: Volumes of gaseous reactants and products in a chemical reaction are in simple whole-number ratios.
  • Avogadro’s Law: Equal volumes of gases at the same temperature and pressure contain the same number of molecules.
  • Boyle’s Law: At constant temperature, pressure and volume of a gas are inversely proportional (PV = constant).
  • Charles’s Law/Gay-Lussac’s Law: At constant pressure, volume and temperature of a gas are directly proportional (V/T = constant).
  • Ideal Gas Law: PV = nRT
  • Dalton’s Law of Partial Pressures: Total pressure of a gas mixture is the sum of the partial pressures of each gas.

Kinetic Molecular Theory of Gases

  • Gases are composed of tiny particles far apart.
  • Gas particles have negligible volume.
  • No forces of attraction or repulsion between particles.
  • Particles are in constant, random motion.
  • Collisions are elastic.
  • Average kinetic energy is proportional to temperature.

Separation Techniques

  • Decanting: Separating immiscible liquids or a solid and liquid based on density differences.
  • Filtration: Separating a solid from a liquid based on size difference.
  • Crystallization: Separating a solid dissolved in a liquid based on differences in solubility.
  • Distillation: Separating liquids based on boiling point differences.
  • Solvent Extraction: Separating a component by dissolving it in a solvent based on solubility differences.
  • Chromatography: Separating components based on their different speeds through a medium.

Solutions

Vapor Pressure: Pressure exerted by a vapor in equilibrium with its liquid.

Raoult’s Law: The vapor pressure lowering is proportional to the mole fraction of solute.

Boiling Point Elevation and Freezing Point Depression: ΔTb = Kbm and ΔTf = Kfm

Osmotic Pressure: Pressure required to prevent solvent flow across a semipermeable membrane.

Concentration Units

  • Mass %: (mass of solute / mass of solution) x 100
  • Volume %: (volume of solute / volume of solution) x 100
  • Molarity: moles of solute / liters of solution
  • Molality: moles of solute / kg of solvent
  • Mole Fraction (Xs): moles of solute / total moles

Xs + Xsolvent = 1