Solutions, Acids, and Bases Ch 21 & 22. What is a solution? A solution is a mixture that has the...
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Solutions, Acids, and Bases Ch 21 & 22. What is a solution? A solution is a mixture that has the same composition, color, density, and even taste throughout
What is a solution? A solution is a mixture that has the same
composition, color, density, and even taste throughout.
Slide 3
Solutes and Solvents To describe a solution, you may say that
one substance is dissolved in another. The substance being
dissolved is the solute, and the substance doing the dissolving is
the solvent. When a solid dissolves in a liquid, the solid is the
solute and the liquid is the solvent.
Slide 4
How Substances Dissolve Like the particles of any substance,
water molecules are constantly moving. Also, water molecules are
polar which means they have a positive area and a negative area.
Molecules of sugar are also polar.
Slide 5
How Sugar Dissolves Moving water molecules cluster around the
sugar molecules as their negative ends are attracted to the
positive ends of the sugar molecules.
Slide 6
Water molecules pull the sugar molecules into solution.
Slide 7
Water molecules and sugar molecules spread out to form a
homogeneous mixture.
Slide 8
Dissolving Gases Shaking or pouring a solution of a gas in a
liquid causes gas to come out of the solution. An example of a
solution of a gas dissolved in a liquid is a soft drink. Pressure
and temperature affect how much gas is dissolved in the
solution.
Slide 9
What affects the rate of solubility? Stirring Stirring a
solution speeds up dissolving because it brings more fresh solvent
into contact with more solute. The fresh solvent attracts the
particles of solute, causing the solid solute to dissolve
faster.
Slide 10
What affects the rate of solubility? Surface Area Another way
to speed the dissolving of a solid in a liquid is to grind large
crystals into smaller ones. Large crystals dissolve in water slowly
because the amount of surface area is limited. Increasing the
amount of surface area by creating smaller particles increases the
rate of dissolving.
Slide 11
What affects the rate of solubility? Temperature Increasing the
temperature of a solvent speeds up the movement of its particles.
This increase causes more solvent particles to bump into the
solute. As a result, solute particles break loose and dissolve
faster
Slide 12
How much can dissolve? If you continue adding sugar to
lemonade, eventually the point is reached when no more sugar
dissolves and the excess granules sink to the bottom of the
glass.
Slide 13
How much can dissolve? Solubility is the maximum amount of a
solute that can be dissolved in a given amount of solvent at a
given temperature. The amount of a substance that can dissolve in a
solvent depends on the nature of these substances.
Slide 14
Concentration A concentrated solution is one in which a large
amount of solute is dissolved in the solvent. A dilute solution is
one that has a small amount of solute in the solvent.
Slide 15
Types of Solutions A saturated solution is a solution that
contains all the solute it can hold at a given temperature.
Slide 16
Types of Solutions An unsaturated solution is any solution that
can dissolve more solute at a given temperature.
Slide 17
Types of Solutions A supersaturated solution is one that
contains more solute than a saturated solution at the same
temperature.
Slide 18
Particles in Solution Substances that dissolve in water to
produce solutions that conduct electricity are called electrolytes.
All ionic compounds are electrolytes when they are in a liquid
state, or dissolved in water.
Slide 19
Dissolving Without Water Water cannot dissolve all solutes.
Nonpolar solvents are needed to dissolve nonpolar solutes. Nonpolar
materials have no separated positive and negative areas.
Slide 20
Vinegar-and-oil salad dressing has two distinct layers the
bottom layer is vinegar, which is a solution of acetic acid in
water, and the top layer is salad oil.
Slide 21
Remember that water is polar, which means that the positive
areas of the water molecules are attracted to the negative chloride
ions. The water surrounds the charged ions with the oppositely
charged end to separate the ion from the rest of the solute.
Slide 22
Solubility Curves Each line on the graph is called a solubility
curve for a particular substance. You can use a solubility curve to
figure out how much solute will dissolve at any temperature given
on the graph. You need to know how to read a graph like this.
Slide 23
Solubility Curves According to the graph, in 100 g of water: a.
at what temperature will 140 g of sodium chlorate dissolve? b. how
many grams of potassium nitrate will dissolve at 60 C
Slide 24
Acids Although some acids can burn and are dangerous to handle,
most acids in foods are safe to eat. What acids have in common,
however, is that they contain at least one hydrogen atom that can
be removed when the acid is dissolved in water.
Slide 25
Properties of Acids An acid is a substance that produces
hydrogen ions in a water solution. It is the ability to produce
these ions that gives acids their characteristic properties.
Slide 26
Properties of Acids Acids have several common properties. All
acids taste sour. Taste never should be used to test for the
presence of acids. Acids are corrosive.
Slide 27
Bases You do not consume many bases. Some foods, such as egg
whites, are slightly basic. Medicines, such as milk of magnesia and
antacids, are basic, too.
Slide 28
Properties of Bases One characteristic of bases is that they
feel slippery, like soapy water. Bases are important in many types
of cleaning materials.
Slide 29
Properties of Bases Any substance that forms hydroxide ions, OH
, in a water solution is a base. In addition, a base is any
substance that accepts H + from acids.
Slide 30
Strong bases are corrosive, and contact with skin can result in
severe burns. Therefore, taste and touch never should be used to
test for the presence of a base.
Slide 31
Common Bases Some drain cleaners contain NaOH, which dissolves
grease and small pieces of aluminum. The aluminum reacts with NaOH,
producing hydrogen and dislodging solids, such as hair.
Slide 32
Strength and Concentration The terms strong and weak are used
to classify acids and bases. The terms refer to the ease with which
an acid ionizes or base dissociates in solution. Strong acids and
bases ionize or dissociate completely; weak acids and bases ionize
or dissociate only partially.
Slide 33
Strength and Concentration In contrast, the terms dilute and
concentrated are used to indicate the concentration of a solution,
which is the amount of acid or base dissolved in the solution.
Slide 34
pH of a Solution The pH of a solution is a measure of the
concentration of H + ions in it. The greater the H + concentration
is, the lower the pH is and the more acidic the solution is. The pH
measures how acidic or basic a solution is.
Slide 35
pH of a Solution Solutions with a pH lower than 7 are described
as acidic.
Slide 36
pH of a Solution Solutions with a pH greater than 7 are
basic.
Slide 37
Basic or Acidic or Neutral? pH of: 8 14 9 2 pH of: 3 6.9 1 7
Acidic Basic Neutral
Slide 38
Indicating pH An indicator is an organic compound that changes
color in acid and base. For example, the indicator litmus paper
turns red in acid. Bases react with indicators to produce changes
in color. The indicator litmus turns blue in bases.