Solubility POGIL
Molarity POGIL
Dissolving Solids, Liquids and Gases
http://www.inquiryinaction.org/chemistryreview/dissolving/
Investigation 4: Dissolving Solids,
Liquids and Gases
Key concepts for students
● Dissolving applies to solids, liquids, and gases.
● Dissolving involves the interaction between the solvent and the solute.
● The extent to which a substance dissolves in a liquid is a characteristic property of that substance.
● Heat increases the solubility of most solids.
● Heat does not increase the solubility of all solids by the same amount.
● Heat decreases the solubility of most gases.
Learning objectives
Students will be able to:
● Identify and control variables to design and conduct valid experiments.
● Develop a definition of “dissolve” that applies to solids, liquids, and gases.
● Use observations and results of experiments to develop explanations to answer a question.
● Explain that the solubility of a substance depends on the characteristics of both the solute and the
solvent giving each substance a unique solubility.
● Draw pictures and write captions showing the stages of a solid dissolving.
● Explain that heat affects the solubility of solids and gases differently.
Investigation 4: Dissolving Solids,
Liquids and Gases
Investigation questions
Can solids, liquids, and gases all dissolve?
● How can you tell when a substance is dissolved?
● Does colored sugar dissolve equally well in water, vegetable oil, and
alcohol?
● Does cocoa mix dissolve better in hot water or cold water?
● Do salt and sugar dissolve better in hot water than in cold water?
● Do all liquids dissolve in water?
● Can a gas dissolve in a liquid?
● Does temperature have an effect on how quickly dissolved gas
escapes from a soda?
● How can you make a lemon soda that keeps as much carbonation as
possible?
Dissolving - Summary
• Solids, liquids, and gases can all dissolve.
• Dissolving depends on the molecules of the substance doing the dissolving,
called the solvent, and the molecules of the substance being dissolved,
called the solute.
• Dissolving is the process in which these molecules interact and attract each
other to form a solution.
• The extent to which a substance dissolves is a characteristic property of that
substance called its solubility.
• Water is a good dissolver because of its areas of positive and negative
charge. The mutual attraction between water molecules and other
substances with positive and negative charges causes these substances to
dissolve.
Chemical Change
http://www.inquiryinaction.org/chemistryreview/chemical_change/
Acid/Base POGIL
Calculating pH POGIL
Acid:
A substance that
releases H+ ions in
an aqueous solution
“aqueous” means: water
Characteristics of Acids:
 Acids have a sour taste
 Acids react with metals
 Acids contain Hydrogen
 Many are poisonous and
corrosive to skin
H
Strong Acids
(break down completely to give off many H+
ions)
Weak Acids
(only partially breaks down, gives less H+)
Acids and Bases
Acids:
Some common acids in our daily life:
Ethanoic Acid, CH3COOH: found in vinegar, tomato juice
Citric Acid, C6H8O7: found in citrus fruits
Lactic Acid: found in sour milk, yogurt
Tannic Acid: Found in tea
Tartaric Acid: Found in grapes
What about those commonly found in our lab?
Hydrochloric acid, HCl
Sulfuric Acid, H2SO4
Nitric Acid, HNO3
Which of these is found in batteries?
Sulfuric Acid
Base:
A substance that
releases OH- ions in
an aqueous solution
Characteristics of Bases:
 Bases usually taste bitter
 Bases feel slippery
 Bases contain hydroxide ions
 STRONG bases are also poisonous
and corrosive to skin
OH
Common Bases:
Strong Bases
The Formulae
Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Rubidium hydroxide
Caesium hydroxide
Barium hydroxide
Calcium hydroxide
Strontium hydroxide
LiOH
NaOH
KOH
RbOH
CsOH
Ba(OH)2
Ca(OH)2
Sr(OH)2
(Hydroxides of Group 1 and Group 2 Metals
are STRONG)
All others are WEAK
Some bases (VERY FEW)
don’t have OHMost commonly:
ammonia NH3
Reactions between
acids and bases
When and acid and a base
react with each other, the
characteristic properties of
both are destroyed. This is
called neutralization.
Reactions between
acids and bases
General formula for acid base reaction:
Acid + Base → H2O + Salt
“Salt” means any ionic
NOT JUST
compound formed from NaCl !!
an acid/base reaction
Neutralization Reaction Animation
Neutralization
HCl + NaOH → H2O + NaCl
acid
base
water
salt
Neutralization
Another Example
HNO3 + KOH → H2O + KNO3
H NO3
acid
K OH
base
water
salt
Indicators
An indicator is a compound
that will change color in the
presence of an acid or base
Red Litmus-Turns blue in base
Blue Litmus-Turns red in acid
Universal indicator (pH paper)
Used for the full pH range
Phenolphthalein-Turns pink
in base
pH
pH stands for “potential
hydrogen” and is a measure
of how many H+ ions there
are in solution.
The MORE H+ there are, the
LOWER the pH will be.
pH = - log [H+]
pH Scale
Shows the range of H+
concentrations
High H+ concentration
Virtual demonstration - Detecting acid/base
Low H+ concentration
Investigation 5: Chemical Change
Key concepts for students
● Substances react chemically in characteristic ways.
● Evidence that a chemical reaction has occurred includes: production of a gas, change in temperature,
color change, and formation of a precipitate.
● A chemical reaction can be controlled by adjusting the amount of reactants.
● A chemical reaction can result in an increase in temperature (exothermic) or a decrease in
temperature (endothermic).
● The color change of an acid–base indicator can help classify a solution as an acid or a base, identify
when a solution has been neutralized, and compare the amount of acid or base in a solution.
● In a chemical reaction, the bonds holding one atom to another are broken, atoms rearrange, and
then combine in new ways to create one or more different substances.
● In a chemical reaction, the atoms that make up the reactants are never destroyed or disappear. They
rearrange and bond in new ways to form the products.
Learning objectives
Students will be able to:
● Design a testing procedure to compare the chemical reactions of different substances.
● Use the characteristic chemical reactions to identify an unknown substance.
● Recognize that production of a gas, change in temperature, color change, and formation of a precipitate
are evidence of chemical change.
● Use a thermometer and graduated cylinder accurately.
● Control chemical reactions by adjusting the amount of the reactants.
● Use the color changes of an acid-base indicator to classify and compare different substances.
● Determine whether a new substance is created during a chemical reaction.
Investigation 5: Chemical Change
Investigation questions
● Do powders that look the same have the same chemical reactions?
● How can you use the characteristic ways substances react to tell similar-looking
substances apart?
● How can you identify an unknown powder?
● What are the active ingredients in baking powder?
● Aside from bubbling, what else happens during a reaction between baking soda and
vinegar?
● How can you control the amount of gas produced in a baking soda-and-vinegar
reaction?
● Can the temperature increase during a chemical reaction?
● How can you tell if a substance is an acid, a base, or neutral?
● How can you return the color of a red cabbage indicator solution back to blue?
● How can neutralizing acids help you compare the amount of acid in different
solutions?
● What happens when soap is added to hard water?
Chemical Change - Summary
• A chemical reaction happens when one or more substances change into entirely new
substances with different properties.
• The clues of a chemical reaction are production of a gas, change in temperature, color
change, production of a precipitate.
• In a chemical reaction, it takes energy to break the bonds in the reactants and energy is
released when bonds are formed in the products.
• If more energy is required to break the bonds than is released when new bonds are
formed, the reaction is endothermic.