Salt and Vinegar Crystals

Many crystals are formed from ionically attracted elements, also known as salts.  Salts are formed with ionic bonds, or connections between elements.  An ionic bond is formed from elements that are undergoing attraction based on charges.  We can make large colorful salt and vinegar crystals overnight.

The Experiment

You will need:

  • vinegar
  • food coloring
  • salt
  • hot water
  • a sponge
  • a shallow dish

The procedure:

  1. Cut up a sponge and place pieces into the bottom of your shallow dish.  You can do as many or as few sponge pieces as you like.  We used three irregularly shaped sponge pieces from a previous project.
  2. Bring some water to a boil.
  3. Mix 1 cup of the boiling water with 1/4 cup salt and 1 Tablespoon of vinegar.  Stir the salt in and dissolve as much as you can.
  4. Pour the hot salt water over your sponges in the dish and allow the sponges to absorb the water for a moment.
  5. Put one drop of food coloring on each piece of sponge.  You can use all the same color or chose several different colors.
  6. Let the salt water sit overnight.  Check on your salt crystals to see how they are doing.  If you let it sit for longer even more crystals will grow.

The Science

In the case of the salt and vinegar crystals, you are really just growing table salt crystals.  Table salt is made of Sodium (Na) and Chlorine (Cl), so the formula for table salt is NaCl.  The sodium (Na) is in the first column of the Periodic Table.  All elements in the first column of the table have one electron they would very much like to get rid of; these elements are very reactive.  Chlorine (Cl) is in the second to last column of the periodic table.  It has seven electrons orbiting in the outermost level of electrons.  More than anything in the world Chlorine wants to have eight electrons.  It is also very reactive.  Oh, look sodium has one electron it would like to give up and chlorine really wants one more.  They get along just perfectly!

Electrons are negatively charged and protons (in the center of the atom) are positively charged, so when electrons move around the atoms gain charges.  When Sodium loses and electron (-) it becomes positively charged.  When Chlorine gains and electron it becomes negatively charged. As you know, opposites attract.  The sodium and chlorine combine in a violent reaction.

Animation by Tra at the English language Wikipedia, CC license

But when you made your crystals, you didn’t see any reaction at all.  Why not?  Because the sodium and chlorine were never decomposed (separated), they were just dissolved.  Dissolving means that large crystals break down into individual atoms interspersed with the atoms of the liquid they are dissolved in. The dissolved atoms are too small to see so it looks like they just disappear, but they’re there waiting to come out of solution.  That is what happens when you make crystals, the liquid dries up leaving behind large crystals of salt.

Additional Layers

  • Photo by Chris 73 / Wikimedia Commons, CC license

    Not all crystals are salts.  Think of sugar crystals.  Sugar is made from long carbon chains, which are formed with covalent bonds, not salty at all.

  • Salts are necessary for life to do all that body chemistry, but do not make up the actual living tissue of animals or plants.
  • Before you dive in too deeply in chemistry experiments it’s a good idea to start with the basics: the periodic table of the elements, atomic structure, and bonding.  It’s really tough to talk about what is happening in a reaction if your audience doesn’t really know what an atom is.
  • Why is eating too much salt a bad idea for your health?  Learn about the effect of salt on your body and what essential jobs it does too.  How much is the right amount?

More From Layers of Learning

You’ll like the Layers of Learning Chemistry Units.  Start with Unit 1-11.



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