Mixtures and Solutions

Diane Gioia

Bell’s Crossing Elementary

What is a mixture?A mixture is two or more substances that are

mixed together but not chemically combined.

The substances in a mixture each keep their own properties, and they can be separated into their original form.

A bag of snack mix can be separated into raisins, walnuts, peanuts, etc.

Examples of mixtures Vegetable salad Fruit salad Mixture of sand, water,

and marbles Mixture of sand and

iron filings

Mixtures can be separated based on physical properties.

Blood is a mixture of proteins, sugar, oxygen, carbon dioxide, and other substances. The different substances in blood can be separated based on their densities.

What are Solutions?

SolutionsSolutions are composed of substances that

mix so completely that they cannot be distinguished as separate substances.

They can, however, be easily separated back into the separate substances.

A solution is usually a mixture of a solid that dissolves completely in a liquid.

Ex. Sugar in water

Solutions A solution is a special kind of mixture. The substances in a solution dissolve, or

separate into their most basic particles. The particles of one substance are spread

evenly through another. The substances in a solution can be solids,

liquids, or gases.

Examples of a Solution Carbon dioxide

bubbles in a soda. Carbonated water

mixed with lemonade is a solution of solids, liquids, and gases.

Lemon juice, water and sugar crystals. Sugar is the solid, lemon juice is the liquid dissolved together in water.

What makes up a solution?

In a solution, the substance that dissolves is called the solute.

The solvent is the substance in which the solute is being dissolved.

Sugar is the solute and water is the solvent.

*Water is considered the universal solvent.

True or False?

All solutions are mixtures, but not all mixtures are solutions.

TRUE! That's a true statement. All solutions are

mixtures. They are defined as homogeneous mixtures. Solutions might include salt water, soda water, or even metal alloys. Not all mixtures are solutions. If you mix sand and water, you might have a liquid involved, but that doesn't make it a solution. A mixture that includes sand and water would be defined as a heterogeneous mixture. The parts are not distributed evenly throughout the system.

Can you make a list of Mixtures?

How many Solutions can you list?

How do we separate mixtures and solutions?

There are many ways to separate mixtures and solutions.

The method depends on the properties of the different materials in the

mixture.

Make a Lotus

How can you separate the materials in

mixtures and solutions?

SIFTINGOne way to separate the larger materials

from the smaller ones is by sifting. Sifting allows smaller materials to pass

through holes leaving the larger materials behind.

How would you use sifting to separate marbles, safety pins,

sand, and salt?

Magnetic AttractionAfter you have separated the sand and salt from the

bigger materials using sifting – you can use a magnet to pick up the objects made out of certain metals such as paper clips and safety pins.

Could you use a magnet to separate

Sand, marbles, and plastic beads?

Why or why not?

FloatationFloatation is using a liquid to separate

materials of different densities.A material that is less dense will float on a

material that is more dense.Plastic beads are less dense than marbles.

How would you separate marbles from plastic beads using floatation?

Filtration

You can also separate solutions by filtering them. Filtration is separating solids from liquids by passing a mixture through a filter.

Salt dissolves in water while sand does not.

How could you separate salt and sand using water and a filter?

EvaporationAfter you have filtered out the sand from the solution

of salt water, you can use evaporation to separate the salt from the water.

When water evaporates from the mixture, solid salt particles will be left behind.

How would evaporation naturally separate dirt from water in a mud puddle?

Chromatography

Chromatography separates solutions by dissolving them in special liquids.

For example, chromatography can be used to separate substances such as pigments in a leaf like in the picture.

The police department uses chromatography to separate and identify all kinds of substances.

How can we make a solution more or less concentrated?

The concentration of the solution is a measure of the amount of solute compared to the amount of solvent.

If the amount of solute is small compared to the amount of solvent, the solution is said to be dilute.

If the amount of solute is large compared to the amount of solvent, the solution is said to be concentrated.

Concentrations

For example, if you took one gram of salt and added it to 100 grams of water, the solution is dilute.

If the same amount of water has 30 grams of salt, the solution is concentrated.

Rate of DissolvingYou know that salt easily mixes with water by

dissolving in it. But did you know that salt can dissolve at different rates?

The temperature of the water, the size of the salt particles, and how you stir the solution are factors that affect how quickly the salt dissolves.

TemperatureTemperature affects the rate of dissolving in a

solution.The particles of a substance are always

moving. When heat is added, the particles move faster making it dissolve faster in a liquid.

Think about adding sugar to ice tea vs. hot tea. Which one dissolves faster?

Particle SizeAnother factor that affects the rate of

dissolving is particle size. The smaller the solute particles are, the faster they dissolve.

If you have ever made a cup of hot chocolate, you dissolved powder into milk.

If you put a piece of a chocolate bar in the milk, it would take a longer time to dissolve.

StirringStirring also affects the rate of dissolving. When adding particles to a liquid, you stir or

shake the liquid. This action makes the solute dissolve more quickly.

What happens if you pour a drink mix into a container without stirring?

Solubility

Solubility 4:15

How is a chemical change different from a mixture?

A compound is a type of matter made of a combination of elements. In a compound, two or more elements are combined chemically.

Water is made up of two atoms of hydrogen and one atom of oxygen.

H20

The proportion of hydrogen and oxygen atoms in water is always the same.

If the proportion of elements in a compound is changed, a new compound is formed.

Both water and hydrogen peroxide are made of hydrogen and oxygen atoms.

However, a molecule of hydrogen peroxide contains two hydrogen atoms and two oxygen atoms.

Hydrogen peroxide is NOT like water and you should not drink it.

H2O2

Separating Compounds When elements combine chemically, they

from compounds with properties that are different from the properties of the individual elements.

These elements cannot be easily separated like in a mixture.

Matter and its Properties

Full video 17:06

( a good review

or watch segment on chemical reactions 1:53)