Grade 8 Integrated Science Chapter 10 Lesson 2 on properties of solutions, solubility, concentration, and understanding the "like dissolves like".

1. Chapter 10.2 – Properties of Solution – p 342-350 – page 1
Vocabulary
• Solvent (343) – the substance that exists in the greatest quantity in a solution
• Solute (343) – All other substances in a solution
• Polar molecule (344) – a molecule with a slightly negative end and a slightly positive end
• Concentration (346) – the amount of a particular solute in a given amount of solution
• Solubility (348) – the maximum amount of solute that can dissolve in a given amount of
solvent at a given temperature and pressure
• Saturated Solution (348) – a solution that contains the maximum amount of solute the
solution can hold at a given temperature and pressure
• Unsaturated Solution (348) - a solution that can still dissolve more solute at a given
temperature and pressure
Parts of Solution
•
_____________________ is the process of mixing one substance into another to form a
solution.
•
There are two terms to refer to the substances that make up a solution
•
•
_______________is the substance that exists in the greatest quantity in a solution
All other substances in a solution are ________________
Air
– What is the solvent?
– What is the solute?
Types of Solutions
•
Solutions can exist is all three states of_______________–
solid, liquid, and gas
•
The state of the ____________________determines the state
of the solution because it exists in the greatest quantity

2. Chapter 10.2 – Properties of Solution – p 342-350 – page 2
Water as a Solvent
•
Water is one of the few substances on Earth that exists ______________in all three states –
solid, liquid, gas
•
•
•
Much of the water found on Earth is not _______________________
Water almost always exists as a ___________________
Why is this?
The Polarity of Water
• A water molecule is a _______________________compound held together by the sharing a
electrons between the atoms
• However the electrons are not __________________ shared
• Electrons in the hydrogen-oxygen bond are pulled more closely
to the ________________________
• This unequal sharing gives the oxygen end of the water molecule
a slight ________________________charge
• It also gives the hydrogen end a slight ________________charge
• Thus, the water molecule is ________________________
•
A polar __________________________is a molecule with a
slightly negative end and a slightly positive end
Like Dissolves Like
• Water is often called the ____________________________solvent because it dissolves many
different substances
• However, water cannot dissolve __________________________
• Polar solvents dissolve _________________________solutes easily
• __________________________solvent dissolve nonpolar solutes easily
– This is summarized by the phrase
“_______________________________________________”
• Because water is a polar solvent, it dissolves most polar and ____________________solutes
Polar Solvents and Polar Molecules
• Rubbing alcohol, or isopropyl alcohol, is a substance that is used as a disinfectant
• Molecules of rubbing alcohol are also
_____________________
• Therefore, when rubbing alcohol and water mix, the positive
ends of the water molecules are attracted to the
__________________ends of the alcohol molecules.
• Similarly the negative ends of the water molecules are
attracted to the _____________________________ends of
the alcohol molecules
• In this way, alcohol molecules dissolve in the solvent

3. Chapter 10.2 – Properties of Solution – p 342-350 – page 3
Polar Solvents and Ionic Compounds
• Many ionic compounds are also soluble in____________________________.
• Recall that ionic compounds are composed of alternating positive and negative ions
– Sodium Chloride (NaCl) is an ionic compound composed of sodium ions (Na+) and
chloride ions (Cl-)
• When sodium chloride dissolves these ions are pulled apart by the water molecules
– The negative ends of the water molecules
attract the positive
_____________________ion
– The positive ends of the water molecule attract
the
______________________________chloride
ions.
Concentration – How much is dissolved
•
Have you ever tasted soup and wished it has more
salt in it?
– In a way your taste buds were measuring the amount, or________________________, of
salt in the soup.
•
Concentration is the amount of a particular ________________in a given amount of solution
– In soup, _____________________ is a solute
– Soup with less salt has a lower concentration of salt
Concentration and Dilute Solutions
• One way to describe the saltier soup id to say that it is more __________________________
• The less saltier soup is more __________________________
• Concentrated and dilute are one way to describe how much solute is dissolved in a solution
– However, these terms don’t tell us the exact ____________________of solute dissolved
Describing Concentration Using Quantity
• A more precise way to describe concentration is to state the quantity of solute in a given
quantity of solution.
• When a solution is made of a solid dissolved in a liquid, such as salt in water, concentration is
the ____________________of solute in a given __________________________of solution.
• Mass is usually stated in ________________and volume is usually stated in liters.
– For example, concentration cam be stated as grams of solute per 1 L of solution
– However, concentration can be stated using ________________unit of mass or volume

4. Chapter 10.2 – Properties of Solution – p 342-350 – page 4
Calculating Concentration – Mass per Volume
•
One way that concentration can be calculated is by the following equation:
– To calculate, you must know the mass of solute and the volume of solution that contains
the mass.
Concentration – Percent by Volume
• Not all solutions are made of a ________________________dissolved in a liquid.
• If a solution contains only liquids or gases, its concentration is stated as the
______________________of solute in a given volume of solution
• In this case, the units of volume must be the_________________________– usually mL or L.
• Because the units match, the concentration can be stated as a_____________________.
• Percent by volume is calculated by _________________________the volume of the solute by
the total volume of the solution and then multiplying the quotient by 100.
What is the percent by volume?
– If there are 1000mL of solution, how much isopropyl alcohol
and water are in the solution?
Solubility – How much can dissolve?
• Have you ever put too much sugar into a glass of iced tea?
– Not all the sugar _____________________________
– This is because these is a _________________________ to how much solute (sugar) can
be dissolved in a solvent (water)
• __________________________________is the maximum amount of solute that can dissolve
in a given amount of solvent at a given temperature and pressure
– If a substance has a high solubility, __________________ of it can dissolve in a given
solvent
Saturated and Unsaturated Solutions
• If you add water to a dry sponge, the sponge _______________________the water.
– If you keep adding water, the sponge becomes__________________. It can’t hold
anymore water
• This is_______________________________, or similar, to what happens when you stir too
much sugar into ice tea
• Some sugar dissolves, but the excess sugar does not dissolve
– The solution is saturated
•
A saturated solution is a solution that contains the _______________________amount of

5. Chapter 10.2 – Properties of Solution – p 342-350 – page 5
solute the solution can hold at a given ____________________________and pressure
•
An ______________________________solution is a solution that can still dissolve more
solute at a given temperature and pressure
Factors that Affect How Much Can Dissolve
•
•
Can you change the amount of a particular solute that can dissolve in a solvent? _________
•
Changing either _____________________or _____________________, changes how much
solute can dissolve in a solvent
Recall the definition of solubility –
– The maximum amount of solute that can dissolve in a given amount of solvent at a given
temperature and pressure
Effect of Temperature
• The solubility of most solid substances
_____________________________with
temperature
– However, some can become
_______________soluble as
temperatures increase
• How does temperature affect the
solubility of a gas in a liquid?
– Recall soda, or soft drinks,
contain carbon dioxide, a gas
solute ___________________in
liquid water
– The warmer the soda the more
____________________ bubbles
out than when it is cold
– This is because the solubility of a gas
in a liquid
_______________________when the
temperature of the solution increases
Effect of Pressure
• What keeps carbon dioxide in an unopened can of soda?
• In a can, the carbon dioxide in the space above the liquid soda is under
__________________
• This causes the gas to move to an area of lower__________________________– the solvent
• The gas moves into the solvent, and a solution is formed
– When the can is opened, this pressure is _________________________and the carbon
dioxide gas leaves the solution.
– *Pressure does not affect the solubility of a __________________________solute in a
liquid

6. Chapter 10.2 – Properties of Solution – p 342-350 – page 6
How Fast a Solute Dissolves
• Temperature and pressure can affect how _______________________ solute dissolves
• If solute and solvent particles come into contact more often, the solute dissolves
_________________________
• There are three ways to increase how often solute particles contact solvent particles
– ____________________
– Crushing
• *Stirring and crushing will not make __________________solute dissolve; They will
only increase how fast it dissolves
– Increasing ___________________________________