Lesson 4: MixturesTrail mix is a mixture. A

mixture is a combination of two or more substances that

do NOT form new substances.

There is no chemical reaction though. The particles do not bond

together.You can separate the trail mix into the original ingredient, and these will be unchanged.

Would one substance, like raisins, be considered a mixture?

No. A mixture has to have more than one substance.

Salt water would be a mixture, because the salt and water do not bond to form one substance. They can be separated.

We classify mixtures according to certain properties. There are four

types of mixtures.

A mixture where the different particles are big enough to see is called a…

heterogeneous mixture

Trail mix and tossed salads are examples of heterogeneous mixtures. You can see the separate bits.

A mixture where the particles are too small to see is called a…

homogeneous mixture

Milk and cream cheese are examples of a homogeneous mixture because you can’t see the individual particles.

Some mixtures separate by themselves when their parts settle out into layers.

We call this type of mixture a suspension. A suspension is a

mixture whose particles settle and separate within a few hours.

Oil and vinegar as a salad dressing can be shaken into a smooth-looking mixture. However, the oil lays out on top of the vinegar in a matter of minutes.

If the particles in a mixture are the size of atoms or molecules, the mixture is called a solution. A solution can happen when one

substance dissolves in another, like sugar and water.

All solutions are homogeneous, which means that they have

the same makeup throughout.

Discuss the different types of mixtures, and then we’ll fill in the chart.

Heterogeneous mixture

Homogeneous mixture

Suspension

Solution

A mixture where you can see the particles of different substances

Trail mixTossed salad

A mixture where the individual particles are too small to distinguish and it looks the same throughout.

MilkCream cheese

A mixture whose particles settle and separate over time.

Oil and vinegar

A mixture where the particles are atom-sized and is blended so completely that it looks the same everywhere.

Sugar and water

What are the parts of a solution?

Remember a solution is a mixture where the particles are atom sized, and have the

same makeup

throughout.

There are 2 parts to every solution…

The part that dissolves is called

the

solute

The part that does the

dissolving is called the

solvent

solute

solvent

solution

In solutions, the solvent is always the greater amount.

In the solution of Kool Aid, the water is the

solvent—there’s more of it than

the Kool Aid powder.

Air is another example. Air is 78% nitrogen and 21% of

oxygen. Which one is the solvent?

nitrogen

But there’s a trick with solutions. Have you ever

tried to wipe up a wet spill with a sponge and the sponge gets too full of liquid to soak up any

more?

Solutions are similar.

After a certain amount of solute is dissolved, no more can dissolve.

For example, think about adding sugar to water. If you stir it, the sugar will dissolve. But if you kept adding more and more sugar, soon the sugar would just settle at the bottom. There’s TOO MUCH sugar, and it can no longer dissolve in the water.

The greatest amount of solute that is given amount of solvent can dissolve

is called the solubility of the solute.

The solubility of table salt

in water is 37 grams in 100

grams of water at

room temperature.

If you add more than 37 grams of salt

in this amount of

water, it will not dissolve.

Water solubility is different for each solute.

What are the two parts of a solution?

What is solubility?

Solute = the part that dissolvesSolvent = the part that does the dissolving; the greater part

The greatest amount of solute that can be dissolved in a certain amount of solvent

How can you take mixtures apart?

Physical properties are used to separate mixtures. Ways we can separate mixtures are…

filtration

flotation

solubility

magnetism

FiltrationOne of the most common methods of separating a liquid and a solid is filtration. Filtration separates substances that have particles of different sizes. A filter is a material with small holes. Small particles pass through the holes, large particles do not. For example: coffee filters, air filters

Would you be able to separate a solution using a filter?

No, because all of the particles are atom-sized and they’d just pass right

through!

Flotation

If the 2 substances in a mixture differ in density, it may be possible to use water to separate them by means of flotation.

For example, a mixture of sand and cork chips

may be separated by

pouring in water. The cork

chips have a lower density so it floats to the tope, while the heaver sand

remains at the bottom.

SolubilityLet’s say you have sugar mixed

with sand. Pouring water in the container will dissolve the

sugar, while the sand will remain solid. Then you can filter the sugar solution into another glass to separate it

from the sand. The sugar will then be recovered when the

water in the glass evaporates.

MagnetismIf you have iron bits mixed with sand, for

instance, a magnet can be used to separate the

iron pieces from the sand. The magnet will only attract the metal pieces, while the sand

remains behind.

http://activities.macmillanmh.com/science/ca/grade5/g5_ch7.html

Let’s watch an animated example of each four methods of separating mixtures.

So using these four methods, how would you separate a mixture of sand,

sawdust, iron filings, and sugar?

1) Add water to dissolve the sugar and float the sawdust. Skim the sawdust off.2) Filter the mixture of sugar,

sand, and water, which will take out the sand and the iron filings. Evaporate the water to get the sugar.3) With the sand that is left in

the filter, use a magnet to separate the sand and the iron.

Remember, the parts of a mixture have different physical properties that can be used to separate them.

* density* solubility* magnetism* size

How can you separate a mixture? And what is it about mixtures that allows them to be separated?Filtration, Flotation, Solubility, Magnetism

They can be separated using their physical properties.

Lesson Review1. What kind of substance is a physical combination of 2 or more substances?

A mixture

2. A mixture that settles in layers overnight is a… Suspension

3. Which passes through filter paper without being separated—a suspension or a solution? Why?

A solution passes through filter paper because its particles are the size of molecules and atoms, which is smaller than the filter holes.

4. The part of a solution that is dissolved is called theA.SolventB.CooloidC.EmulsionD.Solute

solute

5. If a mixture contains visible particles, it is…A.a gas.B.homogeneous.C.heterogeneous.D.an element.

heterogeneous

6. A fruit juice container reads, “Shake well before using.” What does this tell you about the juice?

It is a suspension.

A Miss Heavens Production