14.3 Composition of Matter

Mixtures

Essential QuestionWhat Properties Do Solutions Have?

Main IdeaMixtures are made up of two or more pure substances that are not chemically combined. Mixtures can be heterogeneous or homogeneous. Solutions are a type of homogeneous mixture.

I.) MixturesA. A mixture is made up of two or more substances

that are not chemically combined.B. Each substance keeps its original properties.1. Ex: Vegetable soup, trail mix, soil, concrete, fruit salad

C. A mixture does not have a definite compositon

(unlike compounds) and cannot be represented by a

chemical formula.D. Most matter is in the form of mixtures.E. Mixtures can be classified as homogeneous

or heterogeneous 1. A heterogeneous mixture is unevenly

mixeda. You can usually tell a mixture is

heterogeneous by looking at it b/c you can

see the different components.

2. A homogeneous mixture – is evenly mixeda. It appears to be made up of only one kind

of matterb. Ex: air – made up of nitrogen, oxygen, and

small amounts of other gases (CO2 & H2O)

c. Ex: salt water – water and saltd. Ex: steel (a solid) made up of iron, carbon

and other elements

II.) SolutionsA. Solutions are mixtures that are evenly mixed at the molecular level.

1. You can not see the particles that make up a

solution.2. Solutions have 2 parts: a solute and a

solventa. A solute is the substance that is

present in the lesser amountb. A solvent is the substance present

in the greater amount.

Ex: sugar water

3. Substances that make up a solution keep their

properties and can be separated.4. most mixtures are made up of a liquid solvent and

a solid solutea. Ex: water = has dissolved gases and

mineralsb. Ex: brass = a solid mixture of zinc and copper

5. The concentration of the solution – is the ratio of solute to solvent

a. The ratios may vary in a solution

III.) Rate of DissolvingA. Dissolving takes place only at the surface of the solute where the solvent molecules come in contact

with the solute particles.B. Dissolving increases with increased surface area of

the solute and increasing the temperature of the solvent.1. How to increase the surface area of the solvent:

a. Ex: small piece of sugar dissolves faster than a sugar cube

C. Saturated Solution – occurs when no more solute can be dissolved

IV.) AlloysA. An alloy is a solution of one or more metals

and other solids.

1. alloys are made when the component substances

are melted and mixed.a. Brass = 70% copper and 30% zincb. Bronze = 90% copper and 10% tinc. Stainless Steel = 74% iron, 18%

chromium, and

8% nickeld. Sterling Silver = 93% silver and

7% copper

2. Alloys are useful b/c they have different physical properties than the substances they are made of.a. Ex: Bronze = is harder than copper and more durable = also melts at a lower temperature which makes it easier to work withb. Ex: Steel is the combination of iron and carbon1. the more carbon present in steel, the stronger the steel2. the less carbon present in steel, the softer the steel

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