Key Concepts

The polarity that water molecules allows water to dissolve many ionically bonded substances.Salt (sodium chloride) is make from confident sodium ions bonded to negative chloride ions. Water can dissolve salt since the positive part of water molecules attracts the an unfavorable chloride ions and the an adverse part the water molecules attractive the confident sodium ions.The lot of a substance that have the right to dissolve in a liquid (at a specific temperature) is dubbed the solubility of the substance. The substance being liquified is referred to as the solute, and the problem doing the dissolving is called the solvent.

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Students will certainly make a 2-D design of a salt crystal and also use water molecule cut-outs to display how water dissolves salt. After see an computer animation of water dissolving salt, students will certainly compare exactly how well water and alcohol dissolve salt. They will relate their observations to the framework of salt, water, and alcohol top top the molecule level.


Students will be able to explain, ~ above the molecule level, why water have the right to dissolve salt. Student will be able to identify the variables in your experiment. College student will likewise be may be to describe why a much less polar liquid, such together alcohol, is not good at dissolve salt.


Download the student task sheet, and also distribute one every student when specified in the activity. The task sheet will certainly serve as the “Evaluate” ingredient of each 5-E class plan.


Be sure you and also the college student wear correctly fitting goggles. Isopropyl alcohol is flammable. Store it away from flames or spark sources. Read and also follow all warnings on the label. Alcohol have to be disposed of follow to regional regulations.

Materials because that Each Group

Construction paper, any type of colorScissorsTape or glueWaterIsopropyl alcohol (70% or higher)SaltBalance2 clear plastic cups2 small plastic cupsGraduated cylinder

About the materials

You may pick to laminate the water molecules, sodium ions, and also chloride ions located on the last web page of the activity sheet so the you deserve to reuse them with your students following year.


Make a model of a salt crystal.

Project the image Sodium Chloride Crystal.

Remind students that the green balls represent negative chloride ions and the gray balls represent hopeful sodium ions.

Ask students:

What is it around water molecules and also the ions in salt that could make water able to dissolve salt? The confident and an adverse polar end of a water molecule are attracted come the an unfavorable chloride ions and also positive sodium ion in the salt.

Give each college student an activity sheet.

Students will document their observations and also answer questions about the activity on the task sheet. The explain It through Atoms & Molecules and Take It further sections that the task sheet will certainly either be completed together a class, in groups, or individually, depending upon your instructions. Look at the teacher variation of the activity sheet to find the questions and also answers.

Question come Investigate

How does salt dissolve in water?


Activity sheet v sodium and chloride ions and water moleculesConstruction paper, any colorScissorsTape or glue


Make a version of a salt crystalCut the end the ions and water molecules. Kinds the ion on a item of construction document to represent a 2-D salt crystal. Execute not tape these pieces down yet.

Project photo and have students design what happens when salt dissolves in water.

Show student a series of 4 pictures to aid explain the process of water dissolve salt.

Project the picture Sodium Chloride dissolve in Water.

Point the end that numerous water molecules deserve to arrange themselves close to an ion and assist remove the from the crystal. Present students that the optimistic area of a water molecule will certainly be attractive to the an unfavorable chloride ion and also that the an unfavorable area the a water molecule will certainly be attractive to the confident sodium ion.

Model just how water dissolves salt

Look at the pictures showing how water molecules dissolve salt. Climate arrange the water molecules about the sodium and chloride ions in the correct orientation. The positive part of the water molecules need to be near the an adverse chloride ion. The negative part of the water molecules must be near the hopeful sodium ion.

Move the water molecules and also sodium and also chloride ions to model how water disappear salt. Explore

Have students command an experiment to discover out even if it is water or isopropil alcohol would certainly be better at dissolving salt.

Ask student to do a prediction:

Think about the polarity that water molecules and also alcohol molecules. Execute you think alcohol would certainly be just as good, better, or worse 보다 water at dissolve salt?

Discuss just how to collection up a test to compare exactly how water and alcohol dissolve salt. Be sure students determine variables together as:

Amount that water and alcohol usedAmount of salt included to every liquidTemperature of each liquidAmount of stirring

Question to Investigate

Is alcohol just as good, better, or worse 보다 water at dissolve salt?

Materials because that Each Group

WaterIsopropyl alcohol (70% or higher)SaltBalance2 clear plastic cups2 tiny plastic cupsGraduated cylinder


In separate cups, measure two samples of salt that weigh 5 g each.Place 15 mL of water and also alcohol into separate cups.

At the same time, include the water and also alcohol to the samples of salt.

Swirl both cups the same way for around 20 seconds and check for the amount of salt dissolved.Swirl for one more 20 seconds and also check. Swirl because that the last 20 seconds and check. Closely pour turn off the water and alcohol native the cups and compare the lot of undissolved salt left in each cup.

Expected Results

There will certainly be less undissolved salt in the cup with the water 보다 the alcohol. This means that an ext salt liquified in the water than in the alcohol.


Have students to compare the solubility that two different ionic building material in water.

Compare the solubility the the ionic building materials calcium carbonate (CaCO3) and sodium carbonate (Na2CO3) in water.

Ask students:

How could you compare the solubility that calcium chloride and also calcium carbonate? students should indicate measuring equal amounts of every substance and including equal quantities of water at the same temperature.

Question come Investigate

Do every ionic substances dissolve in water?

Materials because that Each Group

Sodium carbonateCalcium carbonateWater2 clear plastic cups2 small plastic cupsBalance


Label two clear plastic cups Sodium Carbonate and Calcium Carbonate.Measure 2 g every of salt carbonate and also calcium carbonate and put lock in their labeled cups.Measure 15 mL that water into each of 2 empty cups.

At the same time, to water the water right into the sodium carbonate and also calcium carbonate cups.

Gently swirl both cups.

Expected Results

The salt carbonate will certainly dissolve, yet the calcium carbonate will not. Define that no all ionically external inspection solids dissolve in water.

Discuss student observations.

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Ask students:

Do every ionic substances dissolve in water? exactly how do you know?Because calcium lead carbonate does not dissolve in water, students have to realize that not all ionic substances dissolve in water.

Explain that on the molecular level, the ion that make up calcium carbonate room attracted so strongly to each other that the attraction through water molecules cannot traction them apart. The is a an excellent thing because calcium lead carbonate is the material that sea shells and bird eggs space made of. Calcium phosphate is another ionic solid the does no dissolve in water. This is also an excellent because that is the material that bones and teeth room made of.

Sodium carbonate division apart fully into ions that are included throughout the water, forming a solution. The sodium and also carbonate ions will not work out to the bottom and cannot be filtered the end of the water.

But calcium carbonate does not break up right into its ions. Rather it is just mixed in through the water. If given sufficient time, the calcium carbonate will resolve to the bottom or deserve to be filtered out of the water. Sodium carbonate dissolved in water is a an excellent example of a solution, and undissolved calcium carbonate is a mixture, not a solution.

Note: The lead carbonate ion is different from the single-atom ion such as sodium (Na+) and also chloride (Cl−) that students have actually seen therefore far. The carbonate ion (CO32−) is written of an ext than one atom. These varieties of ions, called polyatomic ions, are comprised of a group of covalently external inspection atoms that act as a unit. They generally gain or shed one or much more electrons and act together an ion. An additional common polyatomic ion is the sulfate ion (SO42−). This ion is part of Epsom salt as magnesium sulfate (MgSO4) and many fertilizers as potassium sulfate (K2SO4). You have the right to decide if friend would like to present students to these two common polyatomic ions.