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Year 7 - Science

Dissolving

Solutions

Unit Summary

This unit explores the concepts of pure substances, mixtures, and diffusion in liquids and gases. It emphasises accuracy, precision, and the use of appropriate techniques during investigations. The focus is on making predictions and recording reliable observations.

Lesson Summary

You will learn to use the particle model to explain both how solutions form and how solutions differ from a suspension.

Key Notes

  • Suspensions are not solutions, as solid particles can be seen, and eventually will settle over time.
  • Forces of attraction between solute particles have to be overcome for something to dissolve.
  • In a mixture, one particle may fit into spaces between another type, making the total volume less than expected.
  • Not every substance can be dissolved (is soluble) in a solvent.
  • Dissolving is not the same as melting, but both are physical processes.

Vocabulary To Learn

  • dissolve: Occurs when a substance's particles separate and spread throughout the particles of a solvent resulting in it no longer being seen.
  • insoluble: If a substance does not dissolve in a particular solvent, it is described as insoluble.
  • melting: Melting occurs when a substance in the solid state is heated and its particles move into the arrangement of a substance in the liquid state.
  • force of attraction: A force of attraction is a pulling force that keeps things, such as particles, close together.
  • suspension: A mixture of an insoluble solid and liquid in which the solid particles are dispersed in the liquid and settle upon the mixture standing.

Common Mistakes To Avoid

  • Forces of attraction are broken when a substance dissolves.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

Suspensions are not solutions, as solid particles can be seen, and eventually will settle over time. Forces of attraction between solute particles have to be overcome for something to dissolve.

2. Define this scientific word and use it in context. 'dissolve'

Occurs when a substance's particles separate and spread throughout the particles of a solvent resulting in it no longer being seen. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Forces of attraction are broken when a substance dissolves. Correction: Forces of attraction are *overcome*. They are still acting between the particles, but weaker than before so a different particle arrangement.

More Lessons In This Unit

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