This lesson plan aims to teach students how to distinguish between mixtures and pure substances and devise experiments to separate mixtures. The key learning objectives are for students to define the difference between mixtures and substances, and design an experiment to separate an iron filings, sand, and salt mixture. The lesson involves students determining whether slides show mixtures or pure substances, discussing the composition of air, and brainstorming methods to separate the iron, sand, and salt mixture. Assessment will be through listening to group discussions and evaluating their proposed experimental methods.