Disolving lesson

Introduction

• Students discuss conducting a lab experiment.

• The focus is on understanding substances that dissolve in water.

Types of Compounds

Ionic Compounds

• Examples: Salt (NaCl)

• Made of metal ions (Na+) and nonmetal ions (Cl-).

• Dissolving process:

  • Grains break apart into individual ions in water.

  • Positive and negative ions separate due to attraction to water molecules.

• Ionic compounds dissociate when dissolved, resulting in free ions in solution.

Covalent Compounds

• Examples: Sugar (C12H22O11)

• Composed of nonmetals (carbon, hydrogen, oxygen).

• Dissolving process:

  • Grains break apart into individual molecules but do not separate into atoms.

  • Sugar molecules remain whole; they intermingle with water.

• Misconception: Atoms do not float freely in solution; only molecules remain intact.

Dissolving Mechanism

• Polar Nature of Water:

  • Water molecules are polar; they have positive and negative ends.

  • Water's polarity allows it to interact efficiently with ionic and covalent compounds.

• **Dissociation of Ionic Compounds: **

  • Water molecules surround and pull apart ions from the ionic lattice.

Aqueous Solutions

• Denoted by (aq) in chemical equations, indicating a substance is dissolved in water.

• Implications for Ionic Substances:

  • Always assumes dissociation into ions when dissolved.

• **Example Equation:

  • NaCl → Na+ (aq) + Cl- (aq)

Electrical Conductivity

• Conductivity in solutions: ions are necessary for electrical conductivity.

• Acids can dissociate to release H+ ions, contributing to conductivity.

• Everyday example: Lemon juice as an acid supports electricity flow (H+ ions interacting with sensory receptors).

Conclusion

• Distinction between ionic and covalent dissolving processes is crucial.

• Understanding that covalent molecules do not dissociate into individual atoms when dissolved is fundamental for chemistry.