Solubility Rules and Precipitation

Lab Brief #6

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

Mixing two safe things doesn't always make a safe thing.

What you'll learn

All nitrates are soluble, and most sodium, potassium and ammonium salts are too. Most carbonates and hydroxides are not. Mixing two solutions whose exchange would produce an insoluble salt forms a precipitate, which is the basis of many ion tests.

Key words

precipitate
An insoluble solid formed when two solutions are mixed.
ionic equation
An equation showing only the ions that actually take part in forming a product.

Make a hypothesis first

Predict: will the mixture get hotter, colder, or stay the same?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

spotting tile
silver nitrate solution
sodium chloride solution
copper sulfate solution
sodium hydroxide solution
dropping pipettes

Get ready

⚠️ Safety first

Silver nitrate stains skin black and irritates eyes — gloves and goggles throughout.
Collect all waste in the labelled container; silver salts must not enter the drain.

Step 1 of 4 · Read

Think about what you just learned: say what "precipitate" and "ionic equation" mean in your own words before you start.

Step 2 of 4 · Do

Mix pairs of solutions in a spotting tile and record which combinations give a precipitate and its colour. Use your grid plus the solubility rules to write ionic equations for three of the positives.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

Which group of salts is always soluble?

How sure are you?😐 maybe

Question 2 of 2

A precipitate forms when mixing two solutions produces a product that is:

How sure are you?😐 maybe

Mind = blown

💧 Hot water can freeze faster than cold water under the right conditions. Nobody fully understands why.

Nice work!

You got 0 of 2 right.

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✨ More to explore

🌍 Where you see this in real life: Your toothpaste, your soap, even your breakfast involves this.

🏆 Stretch challenge (try it this week): Ask a grown-up to help you mix two safe kitchen things. Predict what will happen first.

👨‍👩‍👧 For the dinner table: “What's something we cook that mixes things together this way?”

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