Fifth Grade · Science · week 2

Dissolving investigations

Investigate what happens when substances dissolve in water and explain dissolving as particles separating and spreading evenly.

When sugar disappears into warm tea, it has not vanished, it has dissolved. Dissolving happens when the particles of a substance, like sugar, separate from each other and spread out evenly among the particles of a liquid, like water. The sugar particles are still there; they are just too spread out and too small to see.

Not everything dissolves the same way. Salt dissolves quickly in warm water and more slowly in cold water, while sand does not dissolve in water at all; it just sinks, because sand particles do not separate and mix into water the way salt particles do. Testing what dissolves, and how fast, is real chemistry.

📋 For the teacher
Teach it (10–15 min):
  • Run the warm-versus-cold dissolving test together in the kitchen; a stopwatch or phone timer makes the comparison concrete.
  • Ask, did it dissolve, or did it just break into smaller pieces? Sand ground finer is still sand, not dissolved.
  • Introduce fair test language: change only one thing, temperature, and keep everything else the same.
  • Let them predict before testing, and talk about whether the result matched the prediction.
Talk about it:
  • What happened to the sugar particles when the sugar dissolved?
  • Why did temperature change how fast the salt dissolved?
  • What is one substance you tried that did not dissolve in water?

Mastery looks like: They can describe dissolving as particles separating and spreading evenly through a liquid, and design a fair test comparing dissolving speed.

Common stumbles: Thinking dissolved sugar has disappeared completely rather than just spread out; confusing dissolved with mixed in but still visible.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Science for this learner.
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