Explicit science instruction
A solution contains solute particles dispersed among solvent particles. Dissolving does not automatically mean a new substance forms; many solution processes are physical dispersions at the particle scale.
Whether a substance dissolves depends on the balance among solute–solute, solvent–solvent, and solute–solvent attractions. The phrase 'like dissolves like' is a useful shortcut, not a complete molecular theory.
Solubility and concentration are different. Solubility describes the maximum amount that can dissolve under specified conditions; concentration describes how much solute is present in a particular solution.
Vocabulary: solute; solvent; dissolving; solubility; concentration.
Worked example with reasoning
When sodium chloride dissolves in water, ions separate and become surrounded by polar water molecules. The particles are dispersed; the salt has not simply melted.
Guided question
How would you distinguish dissolving, melting, and reacting using particle-level evidence?
Independent work
- Draw particle models for solid solute, dissolved solute, and melted substance.
- Classify three scenarios as dissolving, melting, or reacting.
- State one limitation of the phrase 'like dissolves like.'
Misconception check
Dissolving is not synonymous with disappearing; the solute particles remain present in the solution.
Formative understanding check
Does a clear solution prove the solute particles are gone?
Reveal response
No. They are dispersed at scales too small to see directly but remain part of the solution.
Mentor evidence conference
Ask Archaemenes to check unit conversions, model choice, and whether the calculation matches the particle story.
Teacher guidance
Foundation: Use particle diagrams and vocabulary frames.
Core: Explain dissolving and distinguish solubility from concentration.
Extended: Evaluate a case where polarity alone does not fully predict solubility.