Unit: Chemical Interactions
Chapter 8: Solutions
When substances dissolve to form solutions, the
properties of the mixture change.
8.1: A solution is a type of mixture
8.2: The amount of solute that dissolves can vary
8.3: Solutions can be acidic, basic, or neutral
8.4: Metal alloys are solid mixtures
8.1: A solution is a type of mixture
Review / warm-up
 What are their chemical formulas? What are the elements?
 Which is an ionic compound and which is a covalent compound?
 Are the properties of each compound the same/different than the
atoms/elements that form them?
 What is the different in how these compounds are held together?
C
Na
Cl
O
animation
O
8.1: A solution is a type of mixture
8.1 A solution is a type of mixture
8.1: A solution is a type of mixture
The parts of a solution are mixed evenly
 Mixture: a combination of substances – ex: fruit salad, chili
 Can physically separate ingredients because they are not chemically changed –
still the same substances
 If a mixture is so completely blended together…
 The ingredients canNOT be separated and identified as different substances
 Solution: a type of mixture, called a homogeneous mixture
 “same throughout” (“well-mixed”)
 All portions of the the mixture have the same properties
 Sand + Water  Sand sinks to the bottom ; Solution?
 Sugar + water  sugar is dispersed throughout; Solution?
 Other common solutions: seawater, gasoline, liquid part of blood
8.1: A solution is a type of mixture
Solutes and Solvents – components of a
solution
 Solutions – have a definite composition
 Solute – a substance that is dissolved to make a solution
 When it dissolves, it separates into individual particles
 It is dissolved into the…
 Solvent – a substances that dissolves a solute
 Most common: water
 Others – ex: turpentine, soaps - to remove oils
 After the solute dissolves and separates into individual particles, it is
not possible to identify the solute and solvent as different substances
 Ex:
Solution
Salt water
blood
Solute
salt
Calcium ions, sugar
solvent
water
water
8.1: A solution is a type of mixture
A salt water solution
Solute
(salt)
Solvent
(water)
animation
8.1: A solution is a type of mixture
Types of Solutions
 Gas Solution:
 Ex: air = oxygen (an other gases) dissolved in nitrogen
 Liquid Solution:
 Ex: vinegar = acetic acid dissolved in water
 Solid Solution:
 Ex: bronze = tin dissolved in copper
 Must first be melted to a liquid, then mixed, then cooled to solid
 Mixed?
 Ex: soda = carbon dioxide dissolved in water solution
 Ex: saltwater = salt dissolving in water
Solution Worksheet
solute
solvent
8.1: A solution is a type of mixture
Suspensions
 Suspension: the particles added are larger than those found
in a solution, so instead of dissolving, these larger particles
turn the liquid cloudy
 Ex: Flour added to water
 Can sometimes separate the components of the suspension
using a filter
8.1: A solution is a type of mixture
Solvent and solute particles interact
 The parts of a solution are not changed into new substances
 The solute and the solvent can still be physically separated,
though they do interact
 Ex: a solid dissolves in a liquid, the particles of the solute are
surrounded by particles of the liquid (solvent)
 The solute particles become evenly distributed through the solvent
8.1: A solution is a type of mixture
Solvent and solute particles interact (2)

The way a solid compound
dissolves in a liquid depends on
the type of bonds in the
compound

Ionic compounds split apart into
individual ions


Ex: table salt dissolves in water
– the sodium and chloride ions
separate, and each ion is
surrounded by water
molecules
Covalent compounds dissolved
in water, the molecules stay
together and are surrounded by
solvent molecules

Ex: table sugar dissolves in
water – C12H22O11 stays as
such
Properties of solvents change in solutions
 Solutes change the physical properties of a solvent in every
solution
 A solution’s physical properties differ from the physical
properties of the pure solvent
 Dependent on the amount of solute added
Lowering the Freezing Point
 Freezing Point: temperature Liquid  Solid
 A solvent’s freezing point is lowered when a solute is dissolved in it
 Ex: add salt to water – freezing point drops below 32oF (0oC)

Useful for snow and ice on sidewalks and roads (water freezes at a lower temperature,
can help to melt ice)
• A limit: can get down to -6oF (-21oC) before the melted ice will
freeze again
• Ice cream maker:
• Canister surrounding ingredients holds a mixture of salt
and ice
• The lower freezing point causes the ice to melt,
absorbing heat from surroundings
• This includes the ice cream ingredients, which get
chilled
• Then tiny ice crystals form all at once in the ice
cream mixture rather than a few crystals growing
larger over time (as would happen in a regular
freezer)
Raising the Boiling Point
 Boiling Point: temperature liquid  gas
 Boiling point of a solution is higher than the boiling point of the pure solvent
 Solution can remain a liquid at a higher temperature than its pure solvent
 Ex: boiling point of water = 212oF (100oC)
 Salt raises the boiling point of water

Dependent on amount of salt added
 Summary: a solute lowers the freezing point and raises the boiling point of the
solvent in the solution
 Extends the temperature range in which the solvent remains a liquid
 Uses: antifreeze in a car’s radiator (ethylene glycol added to water)
 Prevents the water from freezing in the winter
 Keeps it from boiling in the summer
 s