Comprehensive Notes on States of Matter, Mixtures, and Acids/Alkalis

States of Matter

  • Everything is made of particles too small to see.
  • The three states of matter: solid, liquid, and gas, each with different properties due to particle arrangement and movement.

Solids

  • Particles are held tightly together by strong forces.
  • Particles vibrate but stay in place.
  • Solids have a definite shape and volume.
  • Solids are dense (heavy).
  • Solids cannot be easily compressed (squashed) because particles are closely packed.

Liquids

  • Particles can move past each other, allowing liquids to flow.
  • Particles are held closely together by strong forces.
  • Liquids are dense.
  • Liquids cannot be compressed easily.
  • Liquids can change shape but not volume.

Gases

  • Very weak forces between particles; particles are far apart.
  • Particles move quickly and bounce off each other.
  • Gases have low density (light).
  • Gases do not have a definite shape or volume.

State Changes

  • Heating a solid changes it to a liquid, then to a gas.
  • Cooling a gas changes it back to a liquid, then to a solid.
  • Example: Water
    • Solid (ice): Particles are held firmly but vibrate.
    • Liquid (water): Particles gain energy, vibrations increase until they break apart.
    • Gas (steam): Particles gain enough energy to break free and move quickly.

Gas Pressure and Diffusion

  • Pressure: When a gas is squeezed into a small space (e.g., a balloon), particles bump against the walls, creating pressure.
  • Diffusion: A gas will diffuse (spread out) until it fills any area it's contained in; gas particles diffuse until evenly spread out.

Changes of State and Energy

  • Solid to liquid: Melts with heat absorption.
  • Liquid to gas: Evaporates with heat absorption.
  • Gas to liquid: Condenses with heat release.
  • Liquid to solid: Freezes with heat release.
  • Heat is absorbed when a solid changes to a liquid or a liquid changes to a gas, providing energy for particles to move faster and overcome forces.
  • Heat is released when a gas changes to a liquid or a liquid changes to a solid, as particles lose energy and slow down.
  • Mass remains constant during state changes because the number of particles remains the same.

Compounds

  • Elements join via chemical reactions to form compounds.
  • Compounds have different properties than their constituent elements.
  • Chemical reactions form new substances and involve energy intake or release. Reactions are difficult to reverse.
Chemical Reactions Examples
  • Coal burning:
    CARBON+OXYGEN→CARBON DIOXIDE+HEATCARBON + OXYGEN \rightarrow CARBON\ DIOXIDE + HEAT
    C+O<em>2→CO</em>2+HEATC + O<em>2 \rightarrow CO</em>2 + HEAT
  • Hydrogen exploding:
    HYDROGEN+OXYGEN→WATER+HEATHYDROGEN + OXYGEN \rightarrow WATER + HEAT
    2H<em>2+O</em>2→2H2O+HEAT2H<em>2 + O</em>2 \rightarrow 2H_2O + HEAT
  • Making salt:
    SODIUM+CHLORINE→SODIUM CHLORIDE (salt)SODIUM + CHLORINE \rightarrow SODIUM\ CHLORIDE\ (salt)
    Na+Cl→NaClNa + Cl \rightarrow NaCl
Physical vs. Chemical Changes
  • Firework exploding: Chemical change.
  • Salt dissolving in water: Physical change.
  • Cake baking: Chemical change.
  • Ice melting: Physical change.

Separating Mixtures

  • Mixtures contain substances not chemically joined.
Filtration
  • Separates small solid particles from liquids.
  • Example: Sand and water.
  • The water passes through the filter paper.
  • The filtrate passes through the filter paper and the sand is held back.
  • The sand particles are too big to pass through the pores in the filter paper.
Solubility
  • If a solid dissolves in water, it is soluble.
  • Solute: The substance that dissolves.
  • Solvent: The liquid that it dissolves in.
  • Solution: Sugar has dissolved in the water to form sugar solution.
  • Water is a good solvent because many substances will dissolve in it.
  • Example: Gloss paint requires white spirit, not water, as a solvent because it will not dissolve.

Acids and Alkalis

  • Acids are corrosive (eat into materials).
  • Acids react with some metals to form hydrogen gas and a salt.
  • Acids have a sour taste; many are poisonous.
  • Litmus turns red in acids.
  • Alkalis are the chemical opposites of acids, but some are also corrosive.
  • Alkalis dissolve in water and often have a soapy feel.
  • Alkalis turn litmus blue and neutralize acids.
  • A neutral solution is neither acid nor alkali.
Examples
  • Acids: Hydrochloric acid, sulfuric acid, ethanoic acid (vinegar), citric acid (fruit juices), carbonic acid (soda water).
  • Alkalis: Sodium hydroxide (oven cleaner), soap, sodium bicarbonate (baking powder), washing powder.
Universal Indicator and pH Scale
  • Universal indicator changes color with acids and alkalis to indicate pH.
  • pH scale measures the strength of acids and alkalis (1-14).
  • pH 1-6: Acids (1-3 strong, 4-6 weak).
  • pH 8-14: Alkalis (8-11 weak, 12-14 strong).
  • pH 7: Neutral.
Important Terminology
  • Evaporation: What happens when a liquid turns to gas only at its surface?
  • Dissolved solid: What DS is left behind when a solution is heated?
  • Sodium Chloride: Which SC is a substance found in rock salt?
  • Brine: What B means salty water?
  • Sea salt: What SS is made by evaporating sea water?
  • Boiling: What B is when all parts of a liquid are turning into a gas at once?
  • Boiling Point: Which BP is the temperature at which a liquid boils?
  • Heating to dryness: What HTD is the way to recover the solutes from a solution?