Unit 3 Solutions Chemistry IPC-Solutions-Borders.

Unit 3Solutions Chemistry

IPC-Solutions-Borders

Matter Flowchart

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Colloids SuspensionsIPC-Solutions-Borders

Pure Substances• A pure substance has a

definite composition.• Pure substances can be

elements or compounds


Mixtures

• Combination of 2 or more pure substances.

HeterogeneousNot uniform throughout Homogeneous

Uniform throughoutIPC-Solutions-Borders

SolutionsSolutions, in chemistry, are homogeneous

mixtures of two or more substances.

The substance present in largest quantity usually is called the solvent. The solvent can be either a liquid or a solid.

The substance that is present in smallest quantity is said to be dissolved and is called the solute. The solute can be either a gas, a liquid, or a solid.


Coke lists as its ingredients as: “carbonated water, high fructose corn syrup and/or sucrose, caramel color, phosphoric acid, natural flavors, caffeine”.

What is the solvent?

What are the solutes?

Concept Check


Types of Solutions

Gaseous solutions – air

Liquid solutions – drinks

Solid solutions – steel or other alloys


• Miscible liquids can easily dissolve in one another.

• Immiscible liquids are not soluble in each other.


Miscible and Immiscible Liquids


Heterogeneous Mixtures

Suspensions-contain large particles that “settle out” unless constantly stirred or agitated

Colloids-contain intermediate particles between those in solutions and suspensions


Suspensions

• Heterogeneous Mixture in which the particles in the solvent are so large that they settle out unless the mixture is constantly stirred.


Solutions


Solutions

How does a solid dissolve into a liquid?


How Does a Solution Form?• Solvent molecules are attracted to surface ions.• Each ion is surrounded by solvent molecules.

Ionic solid dissolving in water


Dissolution vs reaction

• Dissolution is a physical change—you can get back the original solute by evaporating the solvent.

• If you can’t, the substance didn’t dissolve, it reacted.

Ni(s) + HCl(aq) NiCl2(aq) + H2(g) NiCl2(s)dry


Factors Affecting Solubility

• Chemists use the saying “like dissolves like”:Polar substances tend to

dissolve in polar solvents.Nonpolar substances tend

to dissolve in nonpolar solvents.

Oil is nonpolar while water is polar. They are immiscible.


Rate of Dissolution

There are several factors that affect the rate or “how quickly” dissolving occurs.

• Heating

• Agitating

• Increasing Surface Area


Saturation


Saturation Typessaturated• solution containing undissolved solute in

equilibrium with the solutionunsaturated• solution containing less than the

maximum amount of solutesupersaturated• solution containing more solute than is

normally allowed


Degree of saturation

• Unsaturated SolutionLess than the

maximum amount of solute for that temperature is dissolved in the solvent.

No solid remains in flask.


Degree of saturation• Saturated solution

Solvent holds as much solute as is possible at that temperature.

Undissolved solid remains in flask.

Dissolved solute is in dynamic equilibrium with solid solute particles.


Saturated Solution


Degree of saturation

• Supersaturated SolutionSolvent holds more solute than is normally

possible at that temperature.These solutions are unstable; crystallization can

often be caused by adding a “seed crystal” or scratching the side of the flask.


A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.

An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.

Sodium acetate crystals rapidly form when a seed crystal isadded to a supersaturated solution of sodium acetate.


Solubility


Solubility of Gases

• In general, the solubility of gases in water increases with increasing mass.

Why?• Larger molecules

have stronger dispersion forces.


Gases in Solution

• The solubility of liquids and solids does not change appreciably with pressure.

• But, the solubility of a gas in a liquid is directly proportional to its pressure.

Increasing pressure above solution forces more gas to dissolve.


Chemistry-Borders

Temperature

Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.


Temperature• The opposite is true of

gases. Higher temperature drives gases out of solution.

Carbonated soft drinks are more “bubbly” if stored in the refrigerator.

Warm lakes have less O2 dissolved in them than cool lakes.


Temperature and Solubility

Solid solubility and temperature

solubility increases with increasing temperature

solubility decreases with increasing temperature


Temperature and Solubility

Gas solubility and temperature

solubility usually decreases with increasing temperature


Electrolytes


Electrolyte

Electrolyte: a substance that dissolves in water to give a solution that conducts electric current

•Any soluble ionic compound is an electrolyte

•Strong acids are electrolytes


Unit 3 Solutions Chemistry IPC-Solutions-Borders.

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