THE COMPLETE BOOK · FREE TO READ
Crystals and Clues
Salt and sand are all mixed up. Vince follows the clues through a sieve, a paper filter and a shrinking pool, discovering that something out of sight can still be there.
Turn the pagesOr scroll to readAll mixed up
Pages 1–2
Salt... and sand. All mixed up!
Explore together · Different materials in one mixture
Vince adds white salt to tan sand. Both kinds of grain are visible together in a clear cup. The two materials begin as visible grains. Mixing them does not make them the same material.
Ask together: What different grains can you see?
Through the sieve
Pages 3–4
I shake my sieve. Both fall through!
Explore together · Compare grains with openings
Vince shakes a coarse sieve. White and tan grains fall into the cup below. In this setup, both kinds of grain fit through the openings. A sieve with different openings could give a different result.
Ask together: What falls through this sieve?
Where did it go?
Pages 5–6
I add water and stir. Where did my salt go?
Explore together · Dissolved does not mean gone
Vince stirs water into the mixture. Tan sand remains at the bottom, but the white salt grains are no longer visible. Enough water dissolves the salt into particles too small to see. The selected sand stays as grains; the salt has not melted or ceased to exist.
Ask together: What can Vince still see in the cup?
A paper filter
Pages 7–8
The sand is still here. I try a paper filter.
Explore together · Choose another tool
Vince points to the sand, then fits clean paper into a funnel seated in an empty receiving cup. The paper and supported funnel prepare a different kind of separation. The sand-bearing cup remains separate until the next pour.
Ask together: What has Vince chosen to try next?
Sand stays behind
Pages 9–10
Sand stays in the paper. The water drips through.
Explore together · Filtering has limits
Vince pours into the supported paper filter. Sand collects in the paper while liquid drips into the cup beneath. Intact coffee paper can hold these sand grains while water and dissolved salt pass through. Clear liquid can still contain dissolved material and is not made safe to drink.
Ask together: What stays in the paper, and what reaches the cup?
A shrinking pool
Pages 11–12
I leave a little pool. Day after day, it shrinks.
Explore together · Water can leave a mixture
Vince pours collected liquid into a shallow blue dish. Over days, the pool becomes smaller. Water escapes into the air as invisible water vapour. Drying time depends on depth, warmth, airflow and humidity; it can take days or longer.
Ask together: What changes as Vince waits?
Crystals as clues
Pages 13–14
White crystals! My salt was here all along.
Explore together · Recover evidence of dissolved salt
Vince looks closely at white crystals left in the blue dish. As water is lost, salt can form new crystals, clusters or a crust. The original grains need not return unchanged.
Ask together: What does the white patch help Vince work out?
Out of sight again
Pages 15–16
A splash of water... Out of sight again. I know where you are.
Explore together · Use a discovery in a new comparison
Vince adds water to a small sample of recovered salt. The sample becomes invisible while a remaining dry patch stays in the dish. A little recovered salt can dissolve again in enough fresh water. The dry patch gives Vince a comparison while he recognizes the clear mixture.
Ask together: Where does Vince think the salt is now?
A quiet notebook
Pages 17–18
For grown-ups
Pages 19–20
For Grown-Ups Vince follows one mixture through several changes. The pictures show visible grains and liquids, not the tiny particles inside them. 1-4 Choosing a tool The openings in this coarse sieve are larger than both kinds of grain, so both pass. Another sieve could behave differently. Compare the holes with the grains before trying. 5-8 Out of sight In enough water, the salt dissolves into particles too small to see. It has not melted or ceased to exist. The selected sand stays as grains. Stirring and waiting help Vince notice the difference. 9-10 What the paper catches An intact, supported coffee filter can hold these sand grains while liquid and dissolved salt pass through. Clear liquid can still contain dissolved material. This does not make it safe to drink. 11-14 The salt returns Water escapes into the air as invisible water vapour. As water is lost, salt can form new crystals. They may make small clusters or a crust; the original grains need not return. Drying can take days or longer, depending on depth, warmth, airflow and humidity. 15-18 Looking again A little recovered salt can dissolve again in enough fresh water. The remaining crystal patch lets Vince compare. His notebook remembers the evidence; no new explanation is needed on the quiet page. Try a little, together With an adult, use a pinch of additive-free salt, washed coarse sand and a few spoonfuls of room-temperature water in a tray. Add enough water for the salt to dissolve. Support coffee paper in a funnel over a clear plastic cup; pour slowly below the paper rim. Leave only a thin layer of filtrate in a shallow dish. Look over several days. Results and crystal shapes vary. Do not taste any mixture or recovered salt. No heating is needed. Keep sand away from eyes, use eye protection when pouring, and wash hands afterwards. These exact props have not had a physical trial. Watching and talking count too. Sources: American Chemical Society, Dissolving and Back Again; UC San Diego, Separating Mixtures; Perkins School for the Blind, Separating a Mixture. Full source checks are retained with the editable edition.
Open these pages in the readerSources and evidence
A coarse sieve whose openings exceed both selected grain sizes lets both salt and sand pass; this attempt need not separate them.
Separating Mixtures: Teacher version
Not all sieves behave alike. This particular sieve has openings larger than the illustrated grains. No claim that every sieve fails or that this exact prop trial occurred.
A small amount of salt dissolves in sufficient room-temperature water while the selected clean sand remains visibly undissolved.
Use additive-free salt and washed coarse sand; appearance varies with impurities. Dissolving is not melting or destruction. Amount must be below capacity; original grain size need not be preserved.
A supported coffee-paper filter retains the selected sand while liquid containing dissolved salt passes through.
Separating Mixtures: Teacher version
The filter must be intact and supported; do not overfill. Extremely fine suspended material may pass. Clear filtrate is not purified drinking water. UCSD incorrectly says atoms: use ions, as supported by ACS. Omit its tasting suggestion and all heating.
Water in an open shallow dish can evaporate into the air while dissolved salt remains and forms visible crystals as the water is lost.
No fixed completion time: allow days, potentially longer with humidity or depth. Small deposits may be crusts or clusters, not large perfect cubes. No visible steam, salt floating away or sunlight as an essential requirement.
Recovered salt can dissolve again when sufficient fresh water is added; recovery shows that clear salt solution contained salt.
Separating Mixtures: Teacher version
The same ions can form new crystals, not necessarily the original grains. Re-dissolve a small recovered sample in ample water. No claim of complete quantitative recovery or safe tasting.
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