1

Solutions

2

E.Q.: WHAT IS A SOLUTION?

3Does a chemical reaction take place when one substance dissolves in another?

No, dissolving is a physical change because no new

substances are formed.

When one substance

dissolves in another,

the resulting mixture is

called a solution.

4

Some DefinitionsSome DefinitionsA solution is a A solution is a

______________________________

- - Mixture of 2 substances Mixture of 2 substances in one phasein one phase

- - Composed of a solvent Composed of a solvent and solute (can be more and solute (can be more than one)than one)

HOMOGENEOUS

5

Parts of a Solution

• Substance dissolved

• Present in smaller amount

• Dissolves the solute

• Present in greater amount

• Determines the state of the solution (solid, liquid, or gas)

Solute + Solvent = Solution (Homogeneous mixture)

Solute Solvent

6

The solute breaks up into tiny particles that spread evenly throughout the solvent. In a solution of sugar water, sugar is the solute, and water is the solvent.

7

Are all solutions liquids?

Many types of solutions are possible. Let’s talk about a few examples….

No!

With your shoulder partner, think of solutions that are not liquids and be ready to share with

the class your examples..

8

Alloy- a mixture done by the melting of two or more metals

9

How do I get solutes to dissolve faster in solvents? Ex. Sugar in iced tea?

With your shoulder partner answer the question and be ready to share with the

class…..

10

How do I get solutes to dissolve faster in solvents? Ex. Sugar in iced tea?Stirring

Increase temperature of solvent

Grind the solute to make it smaller

Fresh solvent contact and interaction with solute

Greater surface area, more solute-solvent interaction

Faster rate of dissolution at higher temperature

11

The Water Molecule

“The Universal Solvent”

12

The Polarity of Water

Water has a simple molecular structure.

Composed of one oxygen atom and two hydrogen atoms.

Each hydrogen atom is covalently bonded to the oxygen via a shared pair of electrons.

13

Electronegativity

• Ability of an atom to attract electrons to itself while bonding to another atom

• Looking at water, which element has a higher electronegativity?

OXYGEN

14

Since oxygen has a higher electronegativity than hydrogen:

• Electrons in molecule get closer to oxygen than with hydrogen

• The oxygen side has a slight or partial negative charge

• The hydrogen side has a slight or partial positive charge.

15

What does this do to the water molecule????

• The partial positive and negative ends of the molecule make it a “polar” molecule

• There is an uneven distribution of electron density in the molecule

16Hydrogen bond:

•Electrostatic attraction between partial positive charge near hydrogen atoms and partial negative charge near oxygen atom

•Weak bonds

•Non-covalent bonds

•Effective solvent

https://www.youtube.com/watch?v=PVL24HAesnc

17

Dissolving process in water

Na+

Cl-

When particles of the solute are completely dispersed and surrounded by particles of the solvent, this process is called SOLVATION.

18

Na+

Cl-

For water: POLAR-POLAR

For NaCl (s): ion-ion

For hydrated ion: Ion-polar

The separation of the ions in an ionic compound (usually by dissolving water) is called DISSOCIATION

19

“Like dissolves like”

–Polar dissolves in polar and ionic

Ex. Salt and Water, sugar and water

–Non-polar dissolves in non-polar

Ex. oil and soap

20

• Definition: The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure.

• Soluble- the solute can be completely dissolved in the solvent

• Insoluble- the solute cannot be dissolved in the solvent. In fact, it separates completely.

SOLUBILITYSOLUBILITY

21

Miscible vs. Immiscible

• When two liquids completely mix they are said to be miscible.

• When two liquids do not mix they are said to be immiscible.

22

• The physical process of converting an atom or a compound into ions by adding or removing electrons. Usually done by a solvent in a solution.

IONIZATIONIONIZATION

23

How do we know ions are present in How do we know ions are present in aqueous solutions?aqueous solutions?

If the solution If the solution

conducts electricityconducts electricity it is called an it is called an ELECTROLYTEELECTROLYTE

Aqueous Solutions Aqueous Solutions (water is the solvent)(water is the solvent)

24

Types of solutes

Na+

Cl-

Strong Electrolyte -100% dissociation,all ions in solution

high conductivity

25

Types of solutes

CH3COOH

CH3COO-

H+

Weak Electrolyte -partial dissociation,molecules and ions in solution: CH3COOH (acetic acid / ethanoic acid)

slight conductivity

26

Aqueous SolutionsAqueous Solutions

Some compounds dissolve in water but Some compounds dissolve in water but do not conduct electricity. They are do not conduct electricity. They are called called NONELECTROLYTES.NONELECTROLYTES.

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol

27

Types of solutes

sugar

Non-electrolyte -No dissociation,all molecules in solution

no conductivity

28

Electrolytes in the BodyElectrolytes in the Body

Carry messages to Carry messages to

and from the brain and from the brain

as electrical signalsas electrical signals

Maintain cellular Maintain cellular

function with the function with the

correct correct

concentrations concentrations

electrolyteselectrolytes

Make your ownMake your own

50-70 g sugar50-70 g sugarOne liter of warm waterOne liter of warm waterPinch of saltPinch of salt200ml of sugar free fruit 200ml of sugar free fruit

squashsquashMix, cool and drinkMix, cool and drink

29

DefinitionsDefinitions

Solutions can be classified as Solutions can be classified as saturated or unsaturated.saturated or unsaturated.

A A saturated solutionsaturated solution-Contains -Contains the the maximummaximum quantity of quantity of solute that dissolves at that solute that dissolves at that temperature.temperature.

An An unsaturated solution-unsaturated solution-ContainsContains less than the less than the maximummaximum amount of solute amount of solute that can dissolve at a that can dissolve at a particular temperatureparticular temperature

30

DefinitionsDefinitions

SUPERSATURATED SOLUTIONSSUPERSATURATED SOLUTIONS contain contain more solute than is more solute than is possible to be dissolvedpossible to be dissolved

Supersaturated solutions are Supersaturated solutions are unstable. The supersaturation is unstable. The supersaturation is only temporary, and usually only temporary, and usually accomplished in one of two accomplished in one of two ways:ways:

1.1. Warm the solvent then cool the Warm the solvent then cool the solution solution

2. Evaporate some of the solvent.http://www.youtube.com/watch?v=XSGvy2FPfCw

31

Solubility Curves

1. What is the solubility of KNO3 at 40°C? ____________

2. What is the solubility of NaNO3 at 60°C? ____________

3. At what temperature can 45 grams of HCl be dissolved in 100 grams of water? ____________

4. At what temperature can KNO3 and NaNO3 have the same solubility? ____________

32

33

Solubility Curves1. What is the solubility of KNO3 at 40°C? ____________

2. What is the solubility of NaNO3 at 60°C? ____________

3. At what temperature can 45 grams of HCl be dissolved in 100 grams of water? ____________

4. At what temperature can KNO3 and NaNO3 have the same solubility? ____________

65-66 grams

125 grams

90°C

67-68°C

34

SupersaturatedSupersaturatedSodium AcetateSodium Acetate

• One application One application of a of a supersaturated supersaturated solution is the solution is the sodium acetate sodium acetate “heat pack.”“heat pack.”