States of Matter and Kinetic Theory

State of Matter

• Properties of Solids, Liquids, and Gases:
  • Compressibility: Solids are difficult to compress, liquids are difficult to compress, and gases are easy to compress.
  • Molecular Packing: Solids have very close packing, liquids have close packing, and gases have widely separated molecules.
  • Shape: Solids have a fixed shape, liquids take the shape of their container, and gases take the shape of their container.
  • Molecular Movement: Solids vibrate in their position, liquids move relatively freely to take the shape of the container, and gases move freely.
  • Attraction Force: Solids have very strong attraction force, liquids have relatively strong forces, and gases have very weak forces.
  • Diffusion: Solids diffuse very slowly, liquids diffuse slowly, and gases diffuse rapidly.

The Kinetic Theory and Change of State

• Kinetic Theory Points:

  • All matter is made up of tiny particles (atoms or molecules).
  • The particles are in constant motion.
  • The higher the temperature, the higher the average energy of the particles.

• Change of States:

  • Melting (Solid to Liquid): When a solid is heated, particles gain kinetic energy, vibrate more, move apart, and the solid melts into a liquid. The melting point is the temperature at which this happens.
  • Boiling (Liquid to Gas): When a liquid is heated, particles gain more kinetic energy, move faster, and overcome attraction forces, escaping into the gaseous phase. This occurs at a constant temperature, the boiling point.
  • Condensation (Gas to Liquid): As gas particles cool, they lose kinetic energy, move slower, and eventually come together to form a liquid state.
  • Freezing (Liquid to Solid): As a liquid cools, particles lose kinetic energy, move more slowly, attraction forces become stronger, and the liquid becomes a solid.
  • Sublimation (Solid to Gas): Some solids change directly into a gas without becoming a liquid when heated. This is called sublimation.

Comparison Between Compound and Mixture

• Compound:
  • Formed of two or more elements in a fixed composition chemically bonded.
  • Made through a chemical reaction.
  • Cannot be separated by physical processes, a chemical reaction is required.
  • Has new properties different from its elements.
• Mixture:
  • Formed of elements or compounds in any composition, not chemically bonded.
  • Made without a chemical reaction.
  • Components can be separated by physical processes.
  • Has the properties of its components.

Separation of Mixtures

• Solid-Solid:
  • Salt and Sand: Dissolve salt in water, filter the mixture.
• Solid-Liquid:
  • Insoluble Solid in Liquid: Use filtration.
  • Soluble Solid in Liquid: Use crystallization or distillation.
• Mixture of Liquids:
  • Miscible Liquids: Use fractional distillation.
  • Immiscible Liquids: Use a separating funnel.

Paper Chromatography

• Used to separate mixtures of coloured materials.
• A baseline is drawn on filter paper, a spot of the mixture is placed on the baseline.
• The paper is placed in a beaker with a small amount of solvent.
• The solvent rises up the paper, carrying the components of the mixture at different rates.
• The separated components can be seen as spots on the paper.
• Rf value (retention factor) is calculated to identify the components.

Solubility

• Definition: The amount of a substance (solute) that can dissolve in a given amount of solvent (usually water).
• Factors Affecting Solubility:
  • Temperature: Solubility increases as temperature increases (for most solids).
  • Pressure: Solubility increases as pressure increases (for gases).
• Solubility Curves: Graphs showing the relationship between the solubility of a substance and temperature.

Solute and Solvent

• Solute: The substance being dissolved.
• Solvent: The substance doing the dissolving.

Extraction of Metals

• Different metals are extracted in different ways, depending on their reactivity.
• Electrolysis: Used for highly reactive metals (e.g., aluminum).
• Reduction: Used for less reactive metals (e.g., iron).

Extraction of Iron

• Iron is extracted from its ore by reducing it with carbon monoxide in a blast furnace.
  • Raw materials include iron ore, coke, limestone, and air.
  • The blast furnace produces molten iron that is further processed to make steel.

Making Steel

• Unwanted impurities are removed from molten iron to create steel.
• Different types of steel exist (mild/low carbon, high carbon, stainless steel) based on carbon content and added elements.
• Steel is stronger and more resistant to corrosion.

Rusting of Iron

• Rusting is an oxidation reaction of iron and oxygen in the presence of water.
• Rust is hydrated iron(III) oxide.
• Prevention methods include painting, oiling, and galvanizing.

Acids and Bases

• Acids: Proton donors (H+ ions). Sour taste, corrosive, turn blue litmus red.
• Bases: Proton acceptors (OH- ions). Bitter taste, soapy feel, turned red litmus blue.
• Neutralization: Reaction between an acid and a base to form a salt and water.
• Indicators: Substances that change color depending on the pH of the solution.
• pH scale measures acidity/basicity.
  • pH 1-3: Strong acid
  • pH 4-6: Weak acid
  • pH 7: Neutral
  • pH 8-14: Base

Titration

• Method to determine the concentration of an unknown acid or base solution using a known concentration of another reagent.
• Done using a burette and an indicator.
• A known amount of one solution dispensed from a burette to reach the endpoint (colour change of the indicator).
• This point shows equal amounts of reactants, thus the unknown concentration can be calculated.

Precipitation

• Method to prepare insoluble salts by combining two or more soluble salts in a solution.
• Insoluble salt formed precipitates.
• This can be used to identify substances in a solution.

Calculations

• Moles:
  • Moles = Mass (g) / Mr
  • Moles = Concentration (mol/dm^3) x Volume (dm^3)
• Empirical Formula: Ratio of elements in the simplest whole number form.
• Molecular Formula: Actual number of atoms of each element in a compound.

Percentage Yield

• Percentage yield is a measure of the efficiency of a chemical reaction.
• It is calculated by dividing the actual yield of a product by the theoretical yield (expected yield) of the product and multiplying by 100.

Energy Changes

• Exothermic Reactions: Release more energy than absorbed (energy out).
• Endothermic Reactions: Absorb more energy than released (energy in).