Chapter 4: Solutions and the EnvironmentScience 14

Packaging and the Environment

http://www.youtube.com/watch?v=nJ3-5XkjSwc

Introduction We use solutions every day without

even realizing it. Many products are sold as concentrates.

How does this affect the environment?

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Introduction When products are sold as concentrates they require less packaging. The production, packaging, and

transportation of solutions requires energy, which often comes from burning fossil fuels. This releases gases into our atmosphere (itself a solution of gases), which then dissolve in water in the air to form acid rain (another solution).

So, less packaging cuts down on waste.

Introduction Chemistry can also help to explain why

shampoo is better to use when washing your hair than soap because it is a weak acid(we will re-visit this later in the chapter).

Acids can be useful, but they also have harmful effects such as contributing to the production of acid rain.

4.1 Use Concentrated Solutions to Reduce Garbage How does your family buy juice?

1 or 2 L containers? Juice crystals? Frozen juice?

Juice crystals and frozen juice are concentrated products.

4.1 Use Concentrated Solutions to Reduce Garbage Concentrated products have a lot of

solute per volume of solvent. To make juice from concentrate, you

need to add water. The result is yummy juice!

4.1 Use Concentrated Solutions to Reduce Garbage

Large containers of ready-made juice are the opposite. They have less solute per amount of solution.

This type of solution is called a dilute solution.

You can drink dilute solutions right from the package, or after adding a small amount of water.

4.1 Use Concentrated Solutions to Reduce Garbage

Dilute solutions have a high water content.

As a result, they require more packaging to hold this amount of water.

We can reduce packaging by using concentrated products so that containers can be used for packaging.

4.1 Use Concentrated Solutions to Reduce Garbage How are concentrated products made?

What are some examples of concentrated products? Juice Instant coffee Canned soups Soup mixes Packaged salad dressings Dehydrated refried beans And many more!

4.1 Use Concentrated Solutions to Reduce Garbage What do all these products have in

common? They come in small packages They are dry or thick

Concentrated products are dry or thick because they are made by removing some or all of the solvent.

When we make them, we need to replace that solvent.

4.1 Use Concentrated Solutions to Reduce Garbage In most cases, water is the solvent. In other cases, the solvent may be oil or

vinegar such as in salad dressing.

4.1 Use Concentrated Solutions to Reduce Garbage Waste Packaging Every day, each person in Canada

throws out about 2.2kg of garbage. That is enough to fill 10 000 garbage

trucks.

4.1 Use Concentrated Solutions to Reduce GarbageWhere does all this garbage come from?

Most of the garbage is made up of paper and yard waste.

Also, food scraps, metals, glass and plastics.

However, 30% of garbage in landfills is product packaging such as plastic wrap, cardboard, and tin.

4.1 Use Concentrated Solutions to Reduce Garbage Not all packaging is wasteful or

undesirable. Some packaging protects food from

contamination and spoilage. Other packaging protects fragile

packages during shipping.

4.1 Use Concentrated Solutions to Reduce Garbage

Packaging also provides valuable consumer information.

Others have special child-proof packaging to prevent children from being poisoned.

Landfills across Canada would last longer if they were not filling up with so much waste packaging.

4.1 Use Concentrated Solutions to Reduce Garbage Practice!

Complete and hand-in the “Check Your Understanding” questions on p. 62

4.2 Acids and Bases Acid – corrosive, sour-tasting substance

that turns blue litmus paper red Has a pH less than 7

Base – slippery, bitter-tasting substance that turns red litmus paper blue Has a pH greater than 7

4.2 Acids and Bases Substances that are neither acids nor bases

are neutral.

When you neutralize an acid or base, you make it neutral.

4.2 Acids and BasesName Uses

Acid Hydrochloric acid

To etch concrete before paintingToilet bowl cleaner

Sulfuric acid To make plastics, fertilizers, dyesCar batteries to conduct electricity

Vinegar (acetic acid)

CookingUsed as a preservative

4.2 Acids and BasesName Uses

Base ammonia Household cleaningFertilizers and explosives

Baking soda Baking (i.e. cookies and cakes) – rises in the ovenantacid

Sodium hydroxide Drain and oven cleanersMakes soaps and detergents

4.2 Acids and Bases Properties of Acids and Bases

Acids Bases

Taste sourChange litmus paper from blue to redReact with metalspH less than 7CorrosiveNeutralize basesConduct electricity

Taster bitterChange litmus paper from red to blueFeel slipperypH more than 7CorrosiveNeutralize acidsConduct electricity

4.2 Acids and Bases Identifying Acids and Bases

Scientists identify acids and bases using indicators.

Indicator – a natural substance that changes colour in the presence of an acid or base.

4.2 Acids and Bases Some flowers are indicators. They change colour depending on the

acidity of the soil. Examples: lichen, cabbage juice, tea,

grape juice However, the most reliable way to identify an acid or a base is to use an indicator such as litmus.

4.2 Acids and Bases Litmus – a dye made from lichen

Litmus paper – convenient indicator strip that has been treated with a weak solution of litmus.

4.2 Acids and Bases pH Scale

pH – tells you how acidic or basic a substance is

pH scale Acids have a pH less than 7 Bases have a pH greater than 7 Substances that fall in the middle of the

scale are neither acidic or basic. They are neutral.

4.2 Acids and Bases

Find milk. The pH of milk is very close to neutral.

4.2 Acids and Bases

As we move to the left of the scale (closer to 0), the substances become more acidic.

As we move to the right (closer to 14), the substances become more basic.

4.2 Acids and Bases

What is the pH of vinegar?

Is vinegar more or less acidic than milk?

4.2 Acids and Bases Practice!

Complete and hand-in the “Check Your Understanding” questions on p. 69

4.3 Acids and Bases in Action Some questions to think about….

What makes cake rise?

How does an antacid help heartburn?

Why does baking soda keep your refrigerator smelling fresh?

4.3 Acids and Bases in Action Baking

Many recipes call for sour milk. Cooks often sour milk by mixing vinegar

or lemon juice into it. When baking soda (a base) and sour milk

(an acid) mix, they quickly form a frothy mass.

4.3 Acids and Bases in Action The reaction releases carbon dioxide gas

in the form of bubbles. This is what makes pancakes, cookies and

cake dough rise.

4.3 Acids and Bases in Action Cooking

In the past, cooks used trial and error to find how to best cook various foods.

Chefs today are still investigating the best cooking methods.

Through careful study they have discovered that pH of the cooking liquid affects the colour and texture of cooked vegetables.

4.3 Acids and Bases in Action Vegetables cooked in basic mixture

soften more easily. This is why chefs often add baking soda

to dried beans before cooking them.

4.3 Acids and Bases in Action Health Care

Heartburn occurs when too much acid is produced in your stomach.

To treat heartburn, some people take an antacid tablet.

4.3 Acids and Bases in Action Antacids are bases that help neutralize the acid in

your stomach. When an acid and a base combine, they cancel

out each other’s properties. The result is a neutral substance. This type of reaction is called neutralization.

4.3 Acids and Bases in Action Deodourizing

Neutralization helps baking soda remove odours from a refrigerator.

Baking soda (a base) cancels out acidic food odours.

4.3 Acids and Bases in Action Combining acids and bases can be

useful. However, it can also be dangerous. Recall from Chapter 1 that bleach

should never be mixed with an acid or a base. This is because bleach forms deadly

fumes when mixed with either an acid (such as a toilet bowl cleaner) or a base (such as ammonia).

4.3 Acids and Bases in Action Corrosion

Substances found at either end of the pH scale are highly corrosive.

They can cause severe burns to the skin and other body tissues.

They can even eat through substances such as metal or rock.

4.3 Acids and Bases in Action Sulfuric acid can be found near one end

of the pH scale (at about 0). Drain cleaners are at the other end. Both are highly corrosive.

How might being corrosive help a drain cleaner work?

4.3 Acids and Bases in Action What affects corrosion?

Corrosion – the wearing away of materials by chemical action

It is also known as rusting. Oxygen is the primary cause of this chemical reaction. However, substances such as acid rain, and salt speed

up the process.

4.3 Acids and Bases in Action The marks on the leaves are

a result of acid rain (rain with a pH less than 5.6).

Many buildings, vehicles and other structures are being corroded by acid rain.

Acid rain is the result of pollutants released by the burning of fossil fuels.

4.3 Acids and Bases in Action Areas near large bodies of

water tend to be very humid (because there are a lot of droplets in the air).

Corrosive substances (such as salt) dissolve in these water droplets.

The water and corrosive substances form a solution that coats surfaces such as cars, buildings and ships.

The coating speeds up corrosion.

4.3 Acids and Bases in Action

Recall: the particle theory states that as particles heat up, they move faster and collide more.

This speeds up all chemical reactions (including corrosion).

Which of these two vehicles will corrode faster? The car in the warm garage!

4.3 Acids and Bases in Action Corrosion at Work

Corrosion accounts for many things such as the colour of minted coins.

When they come fresh from the mint, coins have bright silver or copper colours.

4.3 Acids and Bases in Action With exposure to air, sweat, and other

substances, they become dull and discoloured.

The colours they turn depend on the metals from with they were made.

4.3 Acids and Bases in Action Silver turns black when it

corrodes. Few of today’s coins have much

silver in them, but sterling silver does.

Some silverware and jewelry are made from sterling silver.

That is why good silverware turns black.

Polish can be used to remove the corrosion.

4.3 Acids and Bases in Action Practice!

Complete and hand-in the “Check Your Understanding” questions on p. 73

The End Complete Chapter 4 Review on p. 74 #1-17

Complete and hand-in Chapter 4 Assignment!

The End Review for Unit A Test

Unit A covers chapters 1-4

Complete Unit Review Questions.