Solutions

Part 1: Mixtures

Mixtures of different substances exist all around us. Many of these mixtures are invisible, and we never notice them.

  • Definition: ______– a combination of different substances that is NOT formed by chemical reactions.

•Mixtures can be separated!

Mixtures can be categorized into two groups:

Heterogeneous: Mixtures do not look the same all over

  • Definition: heterogeneous mixture (HT) – a mixture that ______evenly dispersed.

•Dispersed means “spread out”.

•The particles in a HT mixture can be seen.

•Orange juice with pulp is an example of a heterogeneous mixture.

There are a two different types of heterogeneous mixtures:

  • Definition: ______– HT mixture in which particles are floating (suspended) in a fluid.

•Many suspensions do not transmit light and will “settle” over time.

•Examples: Muddy Water, Dusty Air, Orange Juice with Pulp, Salad Dressing

  • Definition: colloid – a suspension made of particles ______to settle out.

•Many colloids do transmit light and will not “settle” over time.

•Examples: Mayonnaise, Milk, Whipped Cream, Butter

Homogeneous mixtures look the same all over.

  • Definition: ______mixture (HM) – a mixture in which the particles are spread evenly.

-The particles that make up a HM mixture cannot be seen.

-Sweet tea is an example of a homogenous mixture.

-There are several different substances (tea, water, and sugar) but you cannot see them.

We can call homogeneous mixtures by another name: solutions.

  • Definition: solution - a HM mixture of 2 or more substances that are ______.

Part 2: Solutions

Solutions are formed by the process of dissolving.

  • Definition: dissolving – the process by which substances ______to form a solution.

When substances dissolve, there are two parts to the solution it creates… The Solute and the solvent.

  • Definition: ______- a substance that gets dissolved and is generally presented in the lesser amount.
  • Definition: ______- a substance that does the dissolving and is generally presented in the greater amount.

•For example: When you stir sugar into water, the sugar dissolves.

-The water is the solvent.

-The sugar is the solute.

  • Definition: ______- occurs when and where the solute and the solvent particles come in contact with each other.

There are three common ways to increase the collisions between the solute and solvent particles and thus increase the rate at which the solute dissolves.

______the surface area: Making a solute smaller makes it dissolve faster.

  • By crushing up a solute, you increase the surface area.
  • The solvent can pull the solute apart faster when it is smaller.

______the mixture: Stirring or shaking will make a SOLIDsolute dissolve faster.

 Increasing the ______: Heating the solvent will make a SOLID solute dissolve faster.

  • Faster moving atoms means faster dissolving!

Did you know?

Liquids dissolve gases best when:

  • The liquid is cold.
  • The liquid is under lots of pressure.

Gases dissolve gases best when:

  • The gas is cold.
  • The gas is under lots of pressure

Part 3: Like Dissolves Like

Water is very good at dissolving things.

Water is known as “The Universal Solvent”

Water can dissolve any______compound, and many ______compounds.

The water molecule has a positive end and a negative end.

This is called being “polar” Because water’s + and – charges are not spread out evenly, it is “polar”.

  • Definition: polar compound – a molecule that has a ______side and a ______side.

Water can only dissolve other polar compounds.

If water cannot dissolve a substance, then that substance is “nonpolar”.

  • Definition: nonpolar compound – has an______charge on its molecules.

The charges are spread out evenly.

  • Nonpolar substances can only dissolve other nonpolar substances.
  • Example – oil-based paint will not dissolve in water. A nonpolar solvent must be used.

General rule: “Like Dissolves Like”.

  • Polar substances can only dissolve other polar substances.
  • Nonpolar substances can only dissolve other nonpolar substances.

Other definitions to know:

  • Definition: ______– when a substance dissolves in a solvent.
  • Definition: Insoluble- When a substance ______dissolve in a solvent.
  • Definition: ______- When two liquids are soluble in each other.
  • Definition: Immiscible- When two liquids are ______in each other.

Part 4: Solubility & Concentration

Some substances dissolve easier than others. This property is called “solubility”

  • Definition: solubility – the ______of a solute that will dissolve in a certain amount of solvent.

•Substances have different solubility.

•Some will dissolve completely in water , while others will dissolve only a small amount.

The amount of solute dissolved in a solvent affects its concentration.

  • Definition: ______– a description of the amount of a solute in a certain amount of solution.

•Think of concentration as being how “strong” a solution is.

•“Concentrated” substances have lots of solute.

•“Diluted” substances only have a little solute.

When a solvent can no longer hold any more solute, we called it “saturated”.

  • Definition: saturated solution – a solution that ______dissolve any more of a solute.
  • Definition: unsaturated – a solution that ______hold more solute.

Sometimes, a solvent can be made to hold more solute than normal. The solution is called “supersaturated”.

  • Definition: supersaturated – a solution that has ______.

•A HOT solution can hold lots of solute.

•When it COOLS, it becomes supersaturated.

•Supersaturated solutions are unstable.

•The extra solute can “fall out” if the solution is shaken!

Part 5: Conductivity

Some solutions have the ability to conduct electricity…

  • Definition: electrolyte – a solution that ______electricity.

•Most electrolytes contain ionic compounds.

•All ionic compounds form electrolytes.

  • Definition: nonelectrolyte – a solution that ______electricity.

•Covalent compounds cannot conduct electricity when dissolved in a solution.