Hold up one clear jar of fully dissolved salt solution (prepared before the lesson so it looks completely clear). Do not tip your hand yet. Take a quick hands tally: gone / still there / not sure. Keep the tone curious, not a test.

Keep the second jar of sand-and-water ready just out of sight for Step 2, when you will bring it out as the mixture example.

Before the lesson: dissolve about 2 teaspoons of table salt in warm water in a clear jar and let it cool so the liquid looks completely clear. Stir a spoon of dry sand into a second clear jar of water so grains are obvious. Set out group trays with cups, funnels, filter paper, shallow dishes and spoons. Print one Investigation Journal page per pupil. Choose a sunny windowsill or a safe warm (not scorching) radiator shelf for the class evaporation dishes, checking plastic dishes will sit stably.

Bring out the sandy jar now so the mixture example is on the board and in pupils' handsight. Hold it beside the clear salt jar. Keep the board light: only mixture and solution plus the big idea that dissolved is not gone. Name filtering and evaporation later in the modelled cycle (Step 4), when pupils can attach each word to an action they are watching.

Misconception to head off: children often say the salt has "vanished" or "turned into water". Name the idea gently: the salt particles are still in the liquid; they are just too small to see. Filtering will not catch dissolved salt; that is why we need evaporation for the salt recovery later in the week.

Nature of STEM: separating mixtures is everyday Chemistry. Chemists and water-treatment workers recover and clean materials using the same big ideas: filter what will not dissolve, and let water evaporate to leave dissolved solids behind.

Use think-pair-share, then a few groups feed back. Predictions are the start of the science, never marked right or wrong. Capture two or three worded predictions on the board so you can return to them later.

Likely ideas: salt has melted; salt has turned into water; salt is still there but tiny; sand will be caught; everything will go through; salt will be caught by the filter too. Do not correct yet. The investigation will settle it.

Key questions: If the salt is still there, why can we not see it? Will filtering get the salt back, the sand back, both, or neither?

Run a full modelled cycle out loud so pupils hear every beat before they work in groups. Name filtering and evaporation here for the first time, attached to the actions they are watching.

I wonder: can we get both the sand and the salt back from water, even when one of them has dissolved?

I predict: the filter will catch the sand because those grains are too big for the tiny holes, but dissolved salt will run through with the water. I think salt crystals will reappear in the dishes when the water slowly dries away.

I test (model only):

• Fold one circle of filter paper into a cone, sit it in a funnel, and rest the funnel in a clear cup on a tray. Name this method: filtering.
• Stir the sand-water jar once, then pour slowly into the filter. Point out the wet sand left in the paper and the cloudy or clearer water below.
• Pour a thin layer of clear salt solution into a shallow dish. Label it with the date. Place it on the chosen sunny windowsill or warm radiator shelf. Name this method: evaporation. Say clearly: no cooker, no kettle, no toaster — slow and safe only. Crystals are days away; today we only start the waiting experiment.

I observed: sand stayed in the paper; water passed through. The salt dish looks empty of solid right now because the salt is still dissolved.

I think: undissolved solids can be filtered out; dissolved solids need the water to evaporate before we see them again. That is why chemists use more than one separating method.

What to expect: filtering is quick and convincing. Crystals usually begin to show within a few school days on a warm sill; full drying can take most of a week in cool Irish weather. If the sill is cold and damp, move dishes to a safe warm radiator shelf or leave them longer and keep checking.

Safety while modelling: work over a tray, wipe spills at once, no tasting, wash hands after handling sand and salt water. If using a radiator shelf, check it is warm not scorching, and that plastic dishes sit stably and cannot slide off.

Before groups start

Each group tray needs: one clear cup of sandy water (about half full), one small cup of clear salt solution, one funnel, one filter paper circle, one empty clear cup, one shallow dish, a label, a pencil, and a tray. Hand out the Investigation Journal page now so groups can note their salt-layer choice as they work. Demonstrate the filter-paper fold once more if needed (circle folded in half, then half again, open into a cone).

The real group decision

Filtering and windowsill evaporation stay as the taught methods. The design choice groups own is the salt layer: how thin to pour and why. Prompt: a deep puddle dries slowly in cool Irish weather; a thin film dries sooner. Groups also agree one simple success check for the sand half (for example: wet sand stays in the paper and the cup below looks clearer). Both the thickness choice and the sand success check go on the journal page.

During the investigation

• Pour slowly so the filter does not overflow.
• If paper tears, start a fresh cone; keep sand off the floor.
• Salt dishes need only a thin layer — deep water takes too long to dry in a cool classroom.
• All dishes go to the same agreed place so the class can check them together over the coming days.
• Do not let groups claim they have "got the salt back" today; the salt recovery is multi-day follow-up.

What good work looks like

Groups can point to sand in the paper, describe the liquid below, explain their salt-layer choice, and say that the salt dish is a waiting experiment. Fold watchers in with questions: Has their filter caught the sand? Why can they not see salt in the dish yet? Was their layer thin enough?

Differentiation

Support: pre-fold one filter cone; give a simple sentence strip — "The filter caught ___. The water went ___." Stretch: ask whether filtering could ever get dissolved salt back, and what evidence would prove it; or compare why two groups chose different thicknesses.

Follow-up across the week

Spend one minute at the start of later days letting the class peer at the dishes. When white crust or crystals appear, name them as the salt that was dissolved all along. That delayed observation is the point of the salt half of the lesson, and it is when the class can finish the salt-recovery conclusion.