Pure Substances and Mixtures Part 2

Explain (using terms, diagrams and examples) the difference between dilute, concentrated and saturated solutions.

A dilute solution contains a small amount of solute that is dissolved. A concentrated solution contains a large amount of solute that is dissolved, and a saturated solution contains the maximum amount of solute that is able to be dissolved in the solvent. For example, a large glass of milk mixed with one squirt of chocolate syrup may be considered a dilute solution. The milk mixed with five squirts may be considered a concentrated solution, and milk mixed with ten squirts of chocolate syrup may become a saturated solution; no more syrup would dissolve.

Solution

A mixture that looks like a pure substance, but is made up of more than one kind of particle. It is made up of two or more pure substances. Also known as a homogeneous mixture

Mechanical Mixture:

A mixture with different parts that you can see. It is made up of different kinds of particles. Also known as a heterogeneous mixture.

What is the difference between pure substances and mixtures, with examples?

A pure substance is made up of only one kind of particle. For example, table sugar only contains sugar particles and distilled water contains only water particles. Mixtures are made up of pure substances combined together. A mixture is composed of at least two different kinds of particles. For example, cow's milk is a mixture composed of water, lactose, fat, protein, minerals and vitamins.

What is the difference between solutions and mechanical mixtures, with examples?

A solution is a mixture that looks like a pure substance, even though it contains more than one kind of particle. The reason that a solution looks like a pure substance is because the particles of the different substances are mixed together evenly. They occur in all of the three states. Examples of solutions include air (gas), ocean water (liquid), and steel (solid). A mechanical mixture is a mixture in which you can see the different parts. This is because the particles of the different substances are not mixed evenly; the particles stay together in groups. Examples of mechanical mixtures include soil, pizza and cereal with milk.

Soluble

Able to dissolve in a specified solvent.

How can you determine the concentration of a solution?

Concentration of a solution = mass of solute (g) / 100 mL volume of solution

Explain (using terms, diagrams and examples) the process of dissolving.

In a solution, one kind of particle (solute) dissolves into the other (solvent). One type of matter mixes into another type of matter to form a homogenous mixture. This occurs because the particles of the solute break apart from one another and the smaller particles fit between the spaces of the larger particles. When a solute dissolves, both the solute and solvent particles are still in the solution, even though it appears to be one substance.

Pure substance

Matter that contains only one kind of particle.

Mixture

Matter that contains two or more pure substances that are combined (mixed) together.

Saturated

Referring to a solution in which the maximum amount of solute has dissolved.

Concentrated Solubility: The maximum amount of solute that will dissolve in a given volume of solvent, at a particular temperature.

Referring to a solution that has a large amount of solute in a given volume of solution.

Dilute

Referring to a solution that has a small amount of solute in a given volume of solution.

Unsaturated

Referring to a solution that still has space for more solute to dissolve.

Homogeneous

Referring to something that is composed of parts that are alike or of the same kind.

Heterogeneous

Referring to something that is composed of parts that are different or not alike.

What are factors that can affect the rate that a solute dissolves in a solvent? Explain.

Some of the factors that can affect the rate that a solute dissolves in a solvent include: a. Temperature: Increasing temperature can increase the solubility rate of a solute, e.g. making hot tea. b. Pressure: Increasing pressure can increase the solubility rate of a solute, e.g. filling a "carbonated drink" with CO2 under pressure. c. Size of solute: Breaking a solute into smaller pieces can increase its solubility rate, e.g. the time it takes sugar granules vs. sugar cubes to dissolve in water. d. Stirring: Stirring will bring more solute and solvent in contact with one another, e.g. mixing concentrated juice in water).

What is the difference between homogeneous and heterogeneous substances?

The differences between homogeneous and heterogeneous substances are the same as the differences between solutions and mechanical mixtures. A homogenous mixture is another name for a solution, and a heterogeneous mixture is another name for a mechanical mixture.

Solvent

The larger part of a solution, into which the solute dissolves.

Solubility

The maximum amount of solute that will dissolve in a given volume of solvent, at a particular temperature.

What does the particle theory explain? What are the five parts of the particle theory discussed in class?

The particle theory explains what matter is composed of, and how it behaves. Fundamentals of the particle theory, discussed in class, include: a. All matter is made up of particles. b. The particles are always moving, to some degree. c. There are spaces between the particles. d. The particles are attracted to one another, to some degree. e. There are different kinds of particles.

Solute

The smaller part of a solution; it dissolves in the solvent.

Identify and describe techniques for separating mechanical mixtures and solutions.

There are various methods for separating mechanical mixtures. The method to use depends on the mechanical mixture being investigated. Examples of techniques include: a. Sorting: Physically separating the parts of a mixture so that similar pieces are together. b. Floating: Lighter parts of a mixture rise to the top of a liquid to be collected. c. Settling: Heavier parts of a mixture sink to the bottom of a liquid to be collected. d. Magnets: Parts of a mixture that are attracted to a magnet can be collected. e. Filters: Smaller parts of a mixture can pass through a sieve or filter to be collected. f. Dissolving: If one part of a mixture dissolves easily in a solvent, it can be separated from the rest of the mixture.

Insoluble

Unable to dissolve in a specified solvent.

There are two major techniques for separating solutions, discussed in class.

a.Evaporation: The process by which a sample of matter changes from a liquid to a gas. If one part of a solution evaporates, it will leave the other part behind to be collected. b. Distillation: A process used to separate liquids in a solution from one another. If one liquid in the solution evaporates more easily than the other, then it can be heated until it evaporates. The gas is then cooled and collected, separate from the other liquid(s) in the solution.