1. 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

2. 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?
NaCl CO2 Sodium Chlorine Carbon Oxygen
NaCl, CO2
Different
An ionic compound is held together by the attraction of oppositely charged ions; a covalent compound its held together by the sharing of pairs of electrons between two atoms C Na Cl O O
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3. 8.1 A solution is a type of mixture
P111 p water, cups, spoon, salt, flour – which substances dissolve in water? (observe after 30 minutes)
The salts dissolved, the flour did not (salt disappeared, flour clouded the water)

4. The parts of a solution are mixed evenly
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

5. Solutes and Solvents – components of a solution
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:
Salt – water
Calcium ions, sugar - water
Solution
Solute
solvent
Salt water
blood
salt
water
Calcium ions, sugar
water

6. A salt water solution Solute (salt) Solvent (water)
8.1: A solution is a type of mixture
A salt water solution
Solute (salt)
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Solvent (water)

7. Types of Solutions Gas Solution: Liquid Solution: Solid Solution:
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

8. Solution Worksheet solute solute solute solute solute solute solute
solvent
solvent
solvent
solvent
solvent
solvent
solvent
solvent

9. 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

10. Solvent and solute particles interact
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

11. Solvent and solute particles interact (2)
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

12. 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

13. 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)

14. 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

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