Working with Solutions and MixturesUnit 2: Chapter 6

Saturated Solution

In this solution no more solute will dissolve at a specific temperature.

All the solvent particles are busy attracting the solute particles that are already dissolved.

Any excess solute will remain undissolved, since there are no water particles available to attract more solute particles away from the solid.

Unsaturated Solution

In this solution more solute can be dissolved at the same temperature.

Solubility

This refers to the mass of a solute that can dissolve in a given amount of solvent to form a saturated solution at a specific temperature.

Example: 35.7 grams of salt per 100 grams of water.

Water in this case will be ice cold (0oC).

The solubility for salt in water is 35.7 g/100 g of water (the greater this number is the more soluble it is in water and the attraction between its own particles is relatively weaker than another substance which may

have its solubility represented by a smaller number)

See Fig 6.2 on P. 150

How much salt will dissolve in 50 grams of water?

Supersaturated Solution

This is a solution that contains more solute than it would normally dissolve at a certain

temperature.

Think: Dew Point!

Preparing a Supersaturated Solutions

You can prepare a supersaturated solution by making a saturated solution at a higher

temperature, then cooling it without stirring. The solute will stay dissolved in the cooler

solution for a short time.

Seeding

Adding a crystal of solute to a supersaturated solution is called seeding. This process can be used to discover whether a solution is unsaturated saturated or supersaturated.

Upon being added to a solution, if a seed crystal becomes smaller, this is an unsaturated solution; if it stays the same, this is a saturated solution; if it grows, this is a supersaturated solution.

Think about the particle theory. Attraction of particles!

6.2

Rate of Dissolving

This is the measure of how fast a solute dissolves in a solvent.

Agitation

Basically means stirring or shaking. This helps to spread the particles of a solute throughout a solvent. The particles of the solvent can use their attractive force on a less concentrated solute. The force that the particles of the solvent can exert is greater, so

the solute dissolves more quickly.

See: P.152 – Fig 6.4A and 6.4B

Factors which affect the Rate of Dissolving!

Agitation

Temperature

Size of solute pieces (exposed surface area)

What is the cause and effect relationship that changes the rate at which a solid dissolves in a liquid with respect to each one of these factors?

Using the particle theory, can you explain why each one of these factors causes the rate of dissolving to change?

Solubility of Solids in Liquids

Temperature

Type of Solvent

Solubility of Gasses in Liquids

Temperature

Pressure

Interesting Fact: An increasing in temperature, increases the solubility of a solid in a liquid but decreases the solubility of a gases in a liquid.

Organic Solvents

Solvents that contain carbon are referred to as organic solvents

6.3

Petroleum

It is an oily, flammable liquid found in deposits beneath Earth`s surface. The word petroleum comes from the Latin words petra (rock) and oleum (oil). It literally means oil from rock.

In its natural state this is not a good fuel for lighting because it produces a flame which is very smokey and dim.

Fact: In Canada, up to now, petroleum has been discovered in Ontario, Alberta, and off the coast of Newfoundland.

Oil Deposits

Alberta’s Oil deposits were formed about 350,000,000 years ago during the Devonian period. A shallow sea once covered the area around Leduc. Plant and animal remains fell to the bottom of the sea, decomposed, and, over time, were buried under thick layers of sedimentary rock and compressed to form oil deposits.

Crude Oil Reservoirs

These are found in hollow spaces, and can be several kilometres deep. Tar sands and shale oil seep into porous rock and are more difficult to extract.

Basically crude oil is found in small, sponge-like holes in rocks deep beneath Earth`s surface.

Drilling

Drilling for oil is a complex operation, not without risks. Modern technology has provided techniques for locating promising sites for wells, some of which must be dug several kilometres

deep.

Kerosene

This is a colorless, thin oil distilled from petroleum. It is less dense than water. It is used not only in lamps but also as a solvent, as a carrier in insecticide sprays, and as a fuel in jet engines.

Fact: Dr. Abraham Gesner perfected a process to separate the tar mixture. This resulted in the production of a new liquid fuel which was ideal for lighting. This fuel was easy to pour; it burned with a clear, steady, bright yellow flame, and the flame was nearly smoke free. Gesner named the new fuel Kerosene. He also designed a new kind of lamp to burn this fuel which he had discovered.

Petrochemicals

These are entirely new products made by processing crude (raw) petroleum.

Uses of Petroleum

This is the source of most of the fuels used today to run vehicles and to warm houses.

Important source of lighting (kerosene lamp fuel)

It serves as the raw material in the production of over 500,000 petrochemicals.

Oil Refineries

It is necessary to refine crude oil because petroleum in its natural state consists of different sized particles. This mixture of particles is not very useful and must be separated before it can be used.

Fact: There are currently 19 oil refineries in Canada, which process about 1.6 million barrels of crude oil daily. A barrel of oil is approximately 159L.

Fractional Distillation

This is the process which yields different types of refined oil products.

See: Page 167 – Figure 6.16 (know this process)

Fractional Distillation Process

A two tower structure is used to process petroleum. In the shorter tower, the crude oil is heated until every part of it vaporizes. The hot vapours are pumped into the bottom of the taller tower, where the vapours of the different substances cool and condense at different temperatures as they rise up the tower. Each substance is collected into pipes and sent to other parts of the refinery for further processing.

Fractional distillation vs Water Distillation

Fractional distillation is used to separate a mixture of several liquid substances all with different boiling points. On the other hand, the process of distilling water involves evaporating and condensing water from the mixture, leaving any solid materials behind.

Examples of Processed Petroleum Products

Kerosene

Gasoline

Diesel Fuels

Other types of Petrochemicals

Pumping Oil

As oil forms, it moves upward under pressure through layers of porous sedimentary rock until it reaches a layer of impermeable rock. Impermeable rock has no spaces for liquids to flow through. When the oil has collected in large amounts, it can be removed by drilling a well.

If the oil is under pressure, it will rise up the well without pumping. If the oil does not rise up naturally, however, it may have to be pumped or forced up with injected water, gas, or air.

Ore

An ore is a mineral (or a group of minerals) that contains a valuable substance.

This a natural solid mixture found underground.

Examples: - Gold Ore (white quartzite and yellow gold)

- Iron Ore

Gold

Gold has the greatest density of any mineral, which is why it accumulates at the bottom of streams.

Gold can be combined with other metals to increase its strength and produce a variety of colours.

Among other things gold is valuable because of it scarcity, resistance to corrosion and its softness (which makes it easy to carve).

Karat refers to the purity of gold. 24-karat gold is pure gold.

Gold Mining

Several tonnes of ore are needed to produce 30 grams of gold.

When extracting gold from gold ore, one of the steps involved in the process requires you to add chemicals to the mixture in order to dissolve the gold.

Twice in the 19th century reports of newly discovered gold deposits led to a gold rush. Thousands of people travelled to northern California and Yukon Territory to find gold.

Panning for Gold

Panning for gold requires using settling and sifting to separate the gold nuggets from the sand and gravel in the stream bed. By swirling the mixture in a pan with plenty of water, the lighter pieces of sand and gravel are washed away, leaving the heavier nuggets of pure gold behind.