Unit B-Chapter 2-Lesson 2

How Do Solutions Form?

Forming Solutions

• A solution is a mixture in which the particles of different substances are evenly distributed and are too small to see with the naked eye.
• A solution appears as a single substance.
• The formation of a solution is a physical change.
• The substances that make up the solution retain many of their original properties.

Example:

• When sugar is dissolved in water, its sweet taste remains.

A solvent is a substance that dissolves other materials

A solute is a substance that is dissolved.

Example:

• In a solution of Kool-Aid, the water is the solvent and the sugar flavoring powder is the solute.

All solutions have solvents and solutes.

Types of Solutions

Some common examples of solutions are:

• perfumes
• cooking extracts
• gasoline
• air
• sterling silver
• tooth fillings
• carbonated beverages (such as soda)

• In a solution, the solvent or solute can be solid, a liquid, or a gas.
• Metal alloys are solutions of solids in solids.
• The metals are melted and mixed, and when they harden, the resulting substance looks uniform.
• These alloys are useful because they combine the properties of different metals.

Examples:

Carbonated beverage = carbon dioxide (solute) + water (solvent)

Brass = copper (solute) + zinc (solvent)
Dental Fillings = mercury (solute) + silver (solvent)

A dilute solution describes a solution with a small amount of solute compared to the amount of solvent

Example:

• Kool-Aid with more water than flavoring.

A concentrated solution describes a solution with a large amount of solute compared to the amount of solvent.

Example:

• Kool-Aid with extra flavoring mixed with the water.

Dissolving Faster

• Because the solution process depends on contact between particles of the solvent and particles of the solute, any action that increases the number of collisions between the solvent and the solute particles tends to increase the rate of dissolving.
• Both stirring and heating the solution increase the rate of collisions.
• Breaking the solute into smaller pieces increases the rate of disolving by increasing the surface area of the solute,
• Icreased surface area allows more solvent particles to come in contact with more solute particles.
• Heating the solvent increases the speed of the solvent particles, and they collide with the solute with greater force, knocking particles away from the solute.
• The increased motion of the solvent particles acarries away more solute particles, leaving fresh surface areas exposed.
• Particles in a heated liquid are spaced farther apart, so there is more space between them for solute particles.
• In general, more solute dissolves in a solvent at higher temperatures than at lower temperatures.