SolubilityThe Physical Property of

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SolubilityThe Physical Property of

By Moira Whitehouse, PhD

Solubility is the physical property which describes how easily a substance dissolves (breaks down, become liquid), or if it dissolves at all in another substance.

For this presentation, we will observe some substances that dissolve in water and some that don’t.

Mixtures where some of the ingredients keep their physical properties

AND

Mixtures in which the ingredients lose some of their physical properties

We will also discuss:

•When some substances are placed together in a mixture, they maintain (keep) their physical properties.

•When other substances are mixed, one or maybe both substances lose some of their physical properties.•When one of the two substances that are mixed together dissolves, one, or maybe both substances, will lose some of their properties.

When a substance dissolves in water, the mixture that is formed is called a solution. In a solution:

• the two substances mix evenly

•and, as stated before, one or both of the substances lose some of their physical properties.

In a previous presentation, we discussed the solubility of sugar, sand and salt in water.

Circle the substance (s) that dissolved in water.

Check the substances that did not dissolve in water.

Yes, sugar and salt dissolved in water forming sugar and salt solutions. Sand, on the other hand, did not dissolve in water..

Circle the substance(s) that mixed evenly.Check the substance(s) that did not mix evenly.

Sugar and salt break into molecules and their molecules mix evenly with the water molecules. Since molecules are invisible, we can no longer see the sugar or salt.

If the molecules were greatly magnified, this is how molecules of sugar and water or molecules of salt and water might look.

The molecules of sand do not break apart nor do they mix evenly with the water molecules. When you stop stirring the mixture, the grains of sand sink to the bottom of the container.

This is how the molecules of water and sand might look after the sand settles to the bottom of the container.

When a solid such as sugar or salt dissolves in water, they seems to disappear.

What properties do sugar and salt lose when they dissolve in water?

Yes, they lose their color, their texture and their state of matter.

However, we know that a substance such as sugar or salt is still there because we can taste it—that is a property it does not lose.

Sugar—yummy, tastes sweet Salt—yucky, tastes salty.

Also, if you leave a solution of sugar and water or salt and water out on the counter for several days, what happens? a. The sugar or salt disappear.

b. The sugar or salt water take on a different taste.

c. The water evaporates and sugar or salt crystals form.

d. The sugar and salt evaporate along with the water.

When the water evaporates, crystals of sugar or salt form—the sugar and salt is still there. Only the water changes to a gas. The salt or sugar is left behind as solid crystals.

http://www.bigfoto.com/miscellaneous/photos-16/index.htm

Pawel C

http://www.flickr.com/

crystals of salt crystals of sugar

What about sand?Did sand lose any of its physical properties when it was mixed with water?

When we stopped shaking the mixture of sand and water, the sand settled to the bottom of the flask. It did not lose any of its physical properties when it was mixed with water. It still was a solid, a tan color, and felt gritty.You can separate a substance that settles by pouring off the water or pumping it through a filter.

But water cleans itself. When water mixed with other substances evaporates, the other substances are left behind. As a result, the liquid water droplets that condense as clouds is clean pure water. So is the rain water that falls from these clouds.

http://www.dnr.state.wi.us/org/

Animals live in water. They defecate and urinate in the water. They die and decay in the water. You can imagine the different substances that are dissolved in lake water.

Let’s look at some other substances and see if they dissolve in water.

What about cloves—a spice we put in our food? Does it dissolve in water? What do you think. Let’s look and see.

Did the cloves lose any physical properties when mixed with water?Circle Yes or No

No, cloves do not dissolve in water. They float on top of the water.

How could you separate water and a substance that floats such as cloves?

Yes, you could skim the cloves off the top of the water.

What about Epsom Salts, a substance used in bath salts? Do you think it will dissolve in water? Yes or No

After putting the Epsom salts in the water, thisis what you see. Did Epsom salts dissolve in water? Yes or NoExplain your answer.

What about Borax, a substance often used in detergents and cosmetics?

Do you think it will dissolve in water? Yes or No

Explain the reason for your answer.

Yes, Borax does dissolve in water.

What physical properties did it lose when it was mixed with water?

As you saw, borax is a substance that dissolves in water. The liquid that results from mixing water and Borax is called

a. a moleculeb. a solutionc. a mixtured. both b and c

You can separate borax and water after the borax has dissolved by:

a. Pouring the borax solution through a filter

b. Letting the borax settle c. Letting the water evaporated. Skimming the borax off the water

Yes, you could leave the borax solution out for several days and let the water evaporate. What would be left behind?

Yes, you could leave the solution out and let the water evaporate

Crystals of Borax would be left behind.

Sometimes people bend pipe cleaners into the shape of a snowflake. Then, they dip it in a solution of Borax. Look and see what happens after the water evaporates.

Yes, you could leave the solution out and let the water evaporate

Crystals of Borax would be left behind.

TheDamnMushroom http://www.flickr.com/

A pipe cleaner in the shape of a snowflake dipped in a borax solution. Water evaporated leaving behind crystals of solid borax.

What if we mix Cherry Kool-Aid mix which contains food coloring and cherry flavoring and water?

Will the food coloring and cherry flavoring dissolve in water? Yes or No

Yes, the Kool-Aid mix does dissolve in water—it mixes evenly with the water.

What physical property or properties does the Kool-Aid mix lose?What physical property or properties does it not lose?

•Does lemon juice dissolve In water? Yes or No

What if we mix another liquid with water? For instance lemon juice.

•Will they mix evenly? Yes or No

Yes, lemon juice and water mix evenly and form a solution.

What physical property or properties of lemon juice change when it is dissolved in water?

Now let’s think about mixing another liquid with water? This time we mix oil and water?

•Do oil and water mix evenly?Yes or No

•Does oil dissolve in water?Yes or No

Oil and water do not mix evenly. As soon as you stop shaking the mixture, the oil rises and floats on top of the water.

No, oil does not dissolve in water.

White table vinegar is mixture of water and acetic acid(about 5% acetic acid, 95% water).

acetic acid

• Table vinegar a. is a solution b. is not a solution

•Does acetic acid dissolve in water?

•Explain your answer.

http://commons.wikimedia.org

Crude oil is a mixture of many different liquid substances that are mixed together evenly.

Liquid petroleum gas

chemicals

gasoline for cars

jet fuelparaffin wax

diesel fuel

lubricating fuelwaxes, polishes

ship fueloil for heating homes

tar for roads and roofs

Some substances found in crude oil

The different substances in crude oil are separated by heating the crude oil. Since different substances have different boiling points, each substances boils off at different temperature and thee gas is captured.

http://commons.wikimedia.org

Gases can also dissolve in water. Carbon dioxide is dissolved in all our sodas along with sugar, color and flavoring. It is the bubbles of carbon dioxide in sodas that give the drink its fizz. You cannot see the carbon dioxide in the drink.

However, shake the soda, hit it with a bat or, better yet add some Mentos. The bubbles of carbon dioxide are released as foam.

Jason Pratt www.flickr.commagician13134

Solutions of solids dissolved in water

Solutions of liquids dissolved in water

Solutions of gases dissolved in water.

Carbon dioxide dissolved in the water in soda pop

Carbon dioxide and oxygen dissolved in lakes and oceans

In summary:

•When certain substances mix with water they dissolve.

•When certain substances mix with water they dissolve.

•When a substance dissolves in water the resulting liquid is called a solution.

.

•When certain substances mix with water they dissolve.

•When a substance dissolves in water the resulting liquid is called a solution.

•When a substance dissolves in water, that substance loses some of its physical properties.