Science 14: Chapter #4 –

Solutions and the Environment

Ms. Baier's Science 14 1

Acid Base Neutral Ms. Baier's Science 14 2

4.1 – Concentration & Dilution

Concentration is determined by the ratio

between the mass of solute and the volume

of solvent in a particular solution

Increasing the solute or decreasing the solvent will

concentrate a solution

Decreasing the solute or increasing the solvent will

dilute a solution

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4.1 – Concentration and Dilution

Concentrated products have a lot of solute per

volume of solvent.

More and more products are being sold in

concentrated form.

e.g. Frozen orange juice concentrate

Manufacturers sell concentrated solutions as a

way of reducing their costs.

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4.1 – Concentration and Dilution

Dilute solutions have low solute per

solvent ratios and typically have a high

water content.

Large containers of ready-serve orange juice

are examples of dilute solutions.

e.g. Bottled Gatorade

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4.2 - Acids and Bases

Solutions can be divided into three main

categories:

Acid – is a corrosive, sour tasting substance

that turns blue litmus paper red.

Base – is a slippery, bitter tasting substance

that turns red litmus paper blue.

Neutral – these solutions are neither acid nor

base.

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Venn Diagram:

4.2 - Acids and Bases

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4.2 - Acids and Bases Name Uses

acid Hydrochloric acid Breaks down food in stomach

Toliet bowl cleaner

Etch concrete

acid Sulfuric acid Make plastics, fertilizers & dyes

Conducts electricity in car batteries

acid Vinegar (acetic

acid)

Cooking

As a preservative

base Ammonia Household cleaning

In fertilizers and explosives

base Baking soda

(sodium

bicarbonate)

Makes cakes rise in the oven

In antacids

base Sodium hydroxide In drain and oven cleaners

To make soap and detergents Ms. Baier's Science 14 8

4.2 - Acids and Bases

b) Properties of Acids and Bases

The physical properties of acids and bases

(acids are sour and bases are bitter) are not a

safe or reliable way to identify and classify

solutions.

Scientists use the chemical properties of acids

and bases to identify and classify them. Ms. Baier's Science 14 9

4.2 - Acids and Bases

Scientists can readily identify acids and bases using indicators. An indicator is a natural substance that changes colour

in the presence of an acid or a base.

The most reliable indicator is litmus, a dye made from lichen. Litmus paper is a convenient indicator strip that has been treated with a litmus solution.

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4.2 - Acids and Bases

c) The pH Scale

Chemists have developed a scale that classifies how acidic or basic substances are. This scale classifies substances form 0 to 14.

Greater than 7 = base

Less than 7 = acid

Equal to 7 = neutral

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4.3 – Acids and Bases in Action Uses of Acids and Bases

Baking – Many recipes call for sour milk. Cooks often sour milk with lemon juice. When sour milk (acid) and baking soda mix they form a frothy mass. This reaction makes pancakes, cookie and dough rise.

Cooking – the pH of cooking liquid effects the colour of the cooked vegetables. Vegetables cooked in acid mixtures do not soften and take longer to cook. Those cooked in basic mixtures soften more easily.

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4.3 – Acids and Bases in Action

Health Care – heartburn occurs when too much acid is produced by your stomach. Antacids (basic) neutralize your stomach acid.

Deodorizing – Baking soda (a base) cancels out acid food odours.

Combining acids and bases can be useful; it can also be dangerous!

Remember the reaction caused by mixing bleach and ammonia?

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4.3 – Acids and Bases in Action

Corrosion

Substances found at either end of the pH scale

are highly corrosive.

They can cause severe skin burns and eat through

substances such as rock and metal.

Corrosion is the wearing away of materials by

chemical action.

Oxygen is the primary cause of his reaction.

Substances such as acid rain, salt and water speed up

the process.

• E.g. A car exposed to salt from road slush will rust quickly.

However a battleship at the bottom of the ocean will rust

very slowly. Ms. Baier's Science 14 14

4.3 – Acids and Bases in Action

Corrosion and Metals

Silver – turns black

Copper – turns green

Iron – rusts (orange-brown)

Aluminum – forms a transparent layer on the

surface

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Web Graphic Citations

http://shopuncleharrys.dukestores.duke.edu/images/cooler%20014.jpg

http://www.yummy.com/images/products/minute%20maid%20box%20orange.gif

http://rms.hamp.k12.wv.us/alkire/NeutralNot%20Acid%20or%20BaseCommon%20Examples.jpg

http://www.anr.state.vt.us/dec/waterq/bass/images/bs_acidrain-phscale.gif

http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_59.jpg

http://www.funsci.com/fun3_en/acids/acids_03.jpg

http://www.neoanathema.com/gallery/albums/upload/do_not_lick.jpg

http://www.haruko.ca/pictures/Lissar/tank.jpg/tank.jpg

http://images.allrecipes.com/site/allrecipes/area/community/userphoto/small/16276.jpg

http://static.flickr.com/50/143267874_82c6bb3acb.jpg

http://www.bookofjoe.com/images/p111915b.jpg

http://drberniedental.com/images/concerns/cracked.jpg

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