What Dissolves

• When a solid dissolves, it mixes so completely with a liquid that you cannot see it anymore.
• A substance that dissolves is called soluble — sugar and salt are soluble in water.
• A substance that does not dissolve is called insoluble — sand and chalk powder are insoluble in water.
• Oil does not dissolve in water; it stays separate and floats on top.

Level 1 — Core idea

Verbal: Stir sugar into water and watch it disappear — but taste the water and it is sweet. The sugar is still there, just spread out too small to see.

Symbolic: Dissolve = solid + liquid -> clear solution (solid is still present, just invisible).

Visual: Sand stirred into water stays cloudy at first, then settles as a layer at the bottom — it never disappears.

Level 2 — Going deeper

Soluble substances (sugar, salt) dissolve completely. Insoluble substances (sand, chalk powder, oil) do not dissolve — they settle, float, or stay separate.

NCERT anchor

NCERT Looking Around 3 kitchen activities — dissolving sugar in tea, salt in dal water.

Does sand dissolve in water like sugar does?

Step 1 — Stir sand into water.
Step 2 — Sand sinks and settles; the water does not become clear like a sugar solution.
Answer: **No** — sand is insoluble; it does not dissolve.

If you cannot see salt in water anymore, has it disappeared?

Step 1 — Taste the water; it is salty.
Step 2 — The salt is still present, just spread evenly and too small to see.
Answer: **No** — the salt has dissolved, not disappeared.

• Name one substance that dissolves in water.
• Name one substance that does not dissolve in water.
• What is a soluble substance?
• Stretch: Why does salty water taste salty even though you cannot see the salt?

Revision tip: Ask: "Can I still taste or detect it, even if I cannot see it?" If yes, it dissolved.

Open the Practice tab for graded questions on What Dissolves.