7-2 : Concentration & Solubility

7-2: Concentration & Solubility

Science Standard 8.5.a: Students know physical processes including freezing and boiling, in which a material changes form

with no chemical reaction.

California StandardsScience Standard 8.5.a: Students know

physical processes including freezing and boiling, in which a material changes form with no chemical reaction.

InputSee vocab sheet

Input & ModelingConcentration

To measure concentration, you compare the amount of solute to the total amount of solution.A concentrated solution has a lot of solute

dissolved in a certain amount of solvent.You can make it more concentrated by adding solute or

taking away solventA dilute solution has only a little solute dissolved in

a certain amount of solvent.So to dilute a solution you add more solvent

Concentration can be measured as the percent of solute in solution by volume or mass.

Input & Modeling

Calculating a Concentration To calculate the concentration of a solution, compare the amount of solute to the amount of solution and multiply by 100 percent.

For example, if a solution contains 10 grams of solute dissolved in 100 grams of solution, then its concentration can be reported as 10 percent.

Input & Modeling

Calculating a Concentration Practice Problem

A solution contains 15 ounces of solute dissolved in 60 ounces of solution. What is the concentration of the solution?

15/60 = 0.25

25%

Input & ModelingSolubility

You can identify a substance by its solubility because it is a characteristic property of matter. Solubility is a measure of how much solute can dissolve in a solvent at a given temperature.

If you can continue to dissolve more solute, you still have an unsaturated solution.

If no more solute will dissolve, you have a saturated solution.

Input & ModelingFactors Affecting Solubility

Factors that affect the solubility of a substance include pressure, the type of solvent, and temperature.An increase in pressure increases the solubility of

gases.Ionic and polar compounds usually dissolve in polar

solvents – “like dissolves like”The solubility of most solids increases as

temperature increases.Gases become less soluble in a liquid when the

temperature of the liquid goes up.

Input & ModelingFactors Affecting Solubility

PressureShaken bottle of soda

“like dissolves like”Soap and water cleaned with water based

paintsOil paints cleaned with turpentine

TemperatureSolid

Rock/crystal candy (have to heat water up to add more sugar in it and then cool to get sweet candy)

GasWarm soda going flat faster (Carbon

dioxide escapes faster)

Input & Modeling

Temperature and SolubilityThe solubility of the compound potassium nitrate (KNO3) varies in water at different temperatures.

Input & Modeling

Temperature and Solubility

KNO3 is least soluble at 0ºC.

Reading Graphs:

At which temperature shown in the graph is KNO3 least soluble in water?

Input & Modeling

Temperature and Solubility

Approximately 65 g of KNO3 are needed to saturate a water solution at 40ºC.

Reading Graphs:

Approximately what mass of KNO3 is needed to saturate a water solution at 40ºC?

7-3: Describing Acids & Bases

What are the properties of acids and bases?

Science Standard 8.5.e: Students know how to determine whether a solution is acidic, basic, or

neutral.

Anticipatory Set

What do these two things have in common?

They both have a sour taste because they contain acids.

InputSee vocab sheet

Input & ModelingProperties of Acids & Bases

An acid tastes sour, reacts with metals and carbonates, and turns blue litmus paper red.

PROPERTIES:Sour Taste

Scientist do not use this one to test- too dangerous

Reaction with metalsAcids react with some metals (magnesium,

zinc, iron) to produce hydrogen gasAcids are corrosive

Input & ModelingProperties of Acids & Bases

PROPERTIES:Reaction with carbonates

When mixed with acid it will produce carbon dioxide (gas)

Geologist use this to identify limestone (since it contains carbonates)

Reactions with indicatorsLitmus paper is an example

Input & ModelingProperties of Acids & Bases

A base tastes bitter, feels slippery, and turns red litmus paper blue.

COMMON Bases= calcium and sodium hydroxide, and ammonia

Properties• Bitter taste• Slippery feel

– Be careful touching bases- they can burn your skin

• Reaction with indicators– Bases turn Blue

Input & ModelingREMEMBER…

Input & ModelingUses of Acids & Bases

Acids and bases have many uses around the home and in industry.

You can find acids and bases everywhere!Vitamins (A)Fertilizers(A)Car batteries (A)Cleaning products (B)Baking soda (B)

Baking soda reacts with acid (such as buttermilk) and creates gases to make things light and fluffy

Mixing cement (B)