Solutions

Vocabulary and Concepts

Definitions• Solution - Solution - a uniform, homogeneous mixture

(on the molecular level) that may contain solids, liquids, or gases.

Solvent Solvent – the substance that dissolves the solute; present in a greater amount than the solute.

Solute Solute - substance being dissolved

The solvent is usually in greater quantity and is of the same phase as the resulting solution.

The solute is usually in lesser quantity and may be a different phase than that of the solution.

Solid sugar (solute) is dissolved in liquid water (solvent) to make liquid lemonade (solution).

How does one know which is the solute and which is the solvent?

Solution = Solute + Solvent

• Solute - gets dissolved

• Solvent - does the dissolving

– Aqueous (water)

– Tincture (alcohol)

– Amalgam (mercury)

– Organic (organic solvent)

• Polar

• Non-polar

Dental filling

Example Types of Solutions

Solute Solvent Example

Gas Gas Air ( oxygen in nitrogen)

Gas Liquid Seltzer (CO2 in water)

Liquid Liquid Antifreeze (ethylene glycol in water)

Solid Liquid Ocean water (salt in water)

Liquid Solid Dental filling (mercury in silver)

Solid Solid Sterling silver (copper in silver)

Types of Solutions

• Solid Solutions– Gold jewelry 14/18 carat– solution of gold and

copper– Sterling silver – solution of silver and copper– Two metals in a solution are called ALLOYS

• Gaseous Solutions– Two gases– Air – Mixture of mostly nitrogen and oxygen

Types of Solutions

• Liquid Solutions– Can involve a solid, gas, or liquid solute– Oxygen dissolves easily in water for fish to

“breath”

– Salts (solid) also dissolve

easily in water (sea water)

Types of Solutions

Soluble: Describes a substance that can be dissolved in a given solvent.

Insoluble: Describes a substance that cannot be dissolved in a given solvent.

Miscible: Describes two liquids that are soluble in each other.

Immiscible: Describes two liquids that are not soluble in each other.

More Definitions

Suspension: A type of heterogeneous mixture that contains particles which settle out over time and can be separated from the mixture by filtration.

Colloids: Heterogeneous mixtures containing particles larger than the molecular species in solutions, but smaller than suspension particles. Typical particle sizes are between 1 and 100 nanometers in diameter.

Solubility: The maximum amount of solute that will dissolve in a given solvent at a specific temperature and pressure. Solubility is determined by the nature of the solute and solvent.

Still More Definitions

Solubility Depends on Temperature

solutions colloids suspensions

< 1 nm > 100 nm

-single atoms-small molecules-ions-polyatomic ions

-aggregates of atoms, molecules or ions-macromolecules (proteins)

-clumps of particles,-mineral grains such as sand

Comparison of Solutions, Colloids, and Suspensions

solutions colloids suspensions

< 1 nm > 100 nmLight passage…

Passage of light Scattering in beam Scattering inall directions

Centrifugation can be used to separate solids from liquids

• Spin the sample very rapidly: the denser materials go to bottom.

• Separate blood into serum and plasma – Serum (a clear solution) – Plasma (contains red

blood cells)

Blood

RBC’s

Serum

A

AFTER

Before

B C

If the mixture contains solids and liquids such that the solids part of the mixture would float to the bottom naturally or go to the bottom by centrifugation, then it is a suspension. If not, go to the next step.

If the mixture is transparent (you can see through it), then the mixture is a solution. If not, go to the next step.

If the mixture is slightly hazy or is difficult to see through, it is a colloid. As a check, is it a mixture like milk that you cannot see through?

Rules for DeterminingSolution, Colloid, or Suspension

Making solutions

• In order to dissolve, the solvent molecules must come in contact with the solute.

• Stirring moves fresh solvent next to the solute.

• The solvent touches the surface of the solute.

• Smaller pieces increase the amount of surface area of the solute.

Water Molecule

• How does the polarity of water aid the dissolution of solutes?

O

H

H

Hydrogen bond

• What is a polar molecule?

Dissolution of Solid NaCl

Solvation – Solvation – the process of surrounding solute particles with solvent particles to form a solution.

solute particles are separated and pulled into solution

solute particles are surrounded by solvent particles

Solvation

Polar water molecules interact with positive and negative ions Animation

Dissolving of NaClHH

O

Na+

+

-- + -+

+

-

Cl-

+ -

+

hydrated ions

Dissolving of Salt in Water

NaCl(s) + H2O Na+(aq) + Cl-(aq)

Cl-

ions

Na+

ions Water molecules

Dissolving process in water

Na+

Cl-1. Overcome attractive forces in solid

2. Hydration of soluteOrientation of water molecules around solute

How do I get sugar to dissolve faster in my iced tea?

Stir, and stir, and stir

Add sugar to warm tea then add ice

Grind the sugar to a powder

Fresh solvent contact and interaction with solute

Greater surface area, more solute-solvent interaction

Faster rate of dissolution at higher temperature