Welcome !!!!
• Dr. Leslie Sombers
leslie_sombers@ncsu.edu
Click the link in the email when it arrives.
Under ‘search courses’, type in ‘Lee County
- 2013’.
http://moodle.wolfware.ncsu.edu
In the top left, click Guest Login -->
Create new account.
• Lingjiao Qi
lqi@ncsu.edu
www.saplinglearning.com
In the top right, click orange button
‘register here’.
Enter 51912 as the key code.
Logging into Sapling….
Go to http://saplinglearning.com
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Copyright © Houghton Mifflin
Company.All rights reserved.
Presentation of Lecture Outlines, 2–2
Your assignment:
A. Develop a thinking map or brainstorm a
list to show what you know about
Chemistry.
B. Share your map with your
group/neighbor.
C. Place your map on the wall.
D. With your group, develop a definition for
chemistry. Write it on your sentence strip
and post it for others to see.
What is Chemistry?
• The study of all substances and the
CHANGES they undergo.
• Referred to as the Central Science because
it overlaps so many other sciences.
• It all begins with curiosity!
Pre- test
To assess content knowledge and learning…..
Sorry guys, it’s a requirement!!!!
Copyright © Houghton Mifflin
Company.All rights reserved.
Presentation of Lecture Outlines, 2–5
Some Definitions….
• Hypothesis:
a proposed explanation for a phenomenon. Generally based on observations
• Theory:
Hypothesis that has been tested over long periods
• Variable:
a value that may change within the scope of a given problem
• Fact:
Valid observation. Scientific facts are verified by repeatable experiments.
• Law:
A scientific law is a statement based on repeated experimental observations that
describes some aspect of the world.
Classifying Matter
• Matter is classified by the number of
phases it contains.
• Any part of a system with uniform
composition and properties is called a
phase.
• Matter can be classified as either
Homogeneous or Heterogeneous.
Mixtures
• Mixtures are a physical blend of 2 or more
kinds of matter.
• Mixtures can be either homogeneous
(solutions) or heterogeneous.
• Separation of mixtures is done by physical
means such as magnets, distillation,
chromatography and filtration.
Pure Substances
•A pure substance has a fixed composition .
Elements and compounds are pure substances.
•Unlike mixtures, every sample of a pure substance
has exactly the same characteristic properties and
composition.
Elements and Compounds
An element is a collection of the same type
of atom. They are the simplest form of
matter that can exist under normal lab
conditions.
Compounds consist of two or more elements
that are chemically combined. They can be
separated only by a chemical change.
Making a compound….
Extensive vs. Intensive
Extensive Properties
• Depend on the amount
of matter present
• Mass, volume, length,
height, amount of
energy, etc.
Intensive Properties
• Do not depend on the
amount of matter
present
• Density, boiling point,
melting point, color,
ability to conduct
electricity, etc.
Metric System
• The metric system is based on a base unit that
corresponds to a certain kind of measurement
• Length = meter
• Volume = liter
• Weight (Mass) = gram
• Prefixes plus base units make up the metric
system
– Example:
• Centi + meter = Centimeter
• Kilo + liter = Kiloliter
Metric System
• The three prefixes that we will use the most are:
– Kilo= 1000
– centi = 1/100 (one hundredth)
– milli= 1/1000 (one thousandth)
• How do you remember all of them?
• Kissing Hairy Dark
space dogs causes mono
• King Henry Died by Drinking Chocolate Milk
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
https://www.youtube.com/watch?v=IhtgKHYZti0
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• So if you needed to measure length you would choose meter as your
base unit
– Length of a tree branch
• 1.5 meters
– Length of a room
• 5 meters
• But what if you need to measure a longer distance, like from your
house to school?
– Let’s say you live approximately 10 miles from school
• 10 miles = 16093 meters
– 16093 is a big number, but what if you could add a prefix onto the
base unit to make it easier to manage:
• 16093 meters = 16.093 kilometers (or 16.1 if
rounded to 1 decimal place)
Metric System
• These prefixes are based on powers of 10. What
does this mean?
– From each prefix every “step” is either:
• 10 times larger
or
• 10 times smaller
– For example
• Centimeters are 10 times larger than millimeters
• 1 centimeter = 10 millimeters
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
– Centimeters are 10 times larger
than millimeters so it takes more
millimeters for the same length
1 centimeter = 10 millimeters
Example not to scale
40
1 mm
40
1 cm
41
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
41
Metric System
• For each “step” to right,
you are multiplying by 10
• For example, let’s go from a base unit to centi
1 liter = 10 deciliters = 100 centiliters
( 1 x 10 = 10) = (10 x 10 = 100)
2 grams = 20 decigrams = 200 centigrams
(2 x 10 = 20) = (20 x 10 = 200)
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• An easy way to move within the metric system is by
moving the decimal point one place for each “step”
desired
Example: change meters to centimeters
1 meter = 10 decimeters = 100 centimeters
or
1.00 meter = 10.0 decimeters = 100. centimeters
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• Now let’s try our previous example from meters to
kilometers:
16093 meters = 1609.3 decameters = 160.93
hectometers = 16.093 kilometers
• So for every “step” from the base unit to kilo, we
moved the decimal 1 place to the left
(the same direction as in the diagram below)
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• If you move to the left in the diagram, move the
decimal to the left
• If you move to the right in the diagram, move
the decimal to the right
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• Now let’s start from centimeters and convert to
kilometers
400000 centimeters = ? kilometers
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Metric System
• Now let’s start from meters and convert to centimeters
5 meters = ? centimeters
Base Units
Kilo
(1000)
•
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
centi
(1/100)
milli
(1/1000)
Now let’s start from kilometers and convert to meters
.3 kilometers = ? meters
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
Metric System
• Summary
– Base units in the metric system are meter, liter, gram
– Metric system is based on powers of 10
– For conversions within the metric system, each “step” is 1
decimal place to the right or left
– Using the diagram below, converting to the right, moves the
decimal to the right and vice versa
Base Units
Kilo
(1000)
Hecto
(100)
Deca
(10)
meter
gram
liter
deci
(1/10)
centi
(1/100)
milli
(1/1000)
Standard Metric Prefixes for the SI Units
Copyright © Houghton Mifflin
Company.All rights reserved.
Presentation of Lecture Outlines, 2–24
Matter POGIL
The structure of matter
http://preparatorychemistry.com/KMT_flash.htm
ACS – Inquiry in Action. A guided-inquiry approach.
Purpose: to provide a set of physical science activities to help teach major concepts
in the study of matter and to help students develop their abilities in scientific inquiry
• Developed to work across grades 3-8
• Cover basic concepts with flexibility incorporated
• Common, safe and inexpensive materials
Material is based on the National Science Education Content Standards for Physical
Science and Science as Inquiry
• Scientific questions are their investigation
• Physical properties
• Physical change
• Dissolving solids, liquids and gases
• Chemical change
• States of matter
• Density
Each investigation
• Begins with an intro activity to motivate
discussion
• Together, teacher and students develop a
question to investigate and design an
experiment to answer the question
• Students plan their experiment, record their
results, and draw conclusions.
Goal: students will acquire both the skills of scientific inquiry and the concepts of
the physical science curriculum
Essential Features of Inquiry:
1.
2.
3.
4.
Students begin with a question that can be answered in a scientific way
Students rely on evidence in attempting to answer the question
Students form an explanation to answer the question based on the evidence collected
Students evaluate their explanation
Science as inquiry: Abilities necessary to do scientific inquiry
Science as inquiry: Understandings about scientific inquiry
Physical science content standards
Question to investigate
A question at the beginning of each activity serves as a guide for designing and conducting
the experiments to answer that question. All the activities within an investigation
lead up to or contribute to the overall objective of the investigation.
Procedure
Procedures are examples or models of ways to design and conduct an
experiment to answer the question to investigate. Because student input in the experimental
design is encouraged, the procedure may be modified or completely changed.
The procedure is offered as a guide to show one way an activity can be conducted.
Expected results
The expected results describe what would happen if the activities were
conducted exactly as written. These should be used as a guide, as the procedures students
develop may vary.
Activity sheets
Each activity has a corresponding activity sheet, which guides students as they conduct
the activity. The activity sheets help students plan their experiments, record
their observations, draw conclusions based on observations, offer explanations, and
apply their learning. When needed, the activity sheets also contain science content.
Assessment
One scoring rubric is included with each investigation. This can be used as a formative
assessment of the students’ work on the activity sheets and their performance
doing the hands-on activities that were a part of the investigation. A separate summative
assessment for the investigation, called Review and apply, is included at the
end of each investigation.
The Power of Polarity
• Atoms have a certain number of protons in their nucleus and the same number of
electrons around the nucleus.
• Protons – POSITIVE CHARGE
• Electrons – NEGATIVE CHARGE
• Because the nucleus contains protons, it has an attraction for electrons.
• Since an atom has the same number of positively-charged protons as negatively-charged
electrons, an atom has no overall or net charge. IT IS NEUTRAL.
Water (H2O) is made up of 2 hydrogen atoms bonded
to one oxygen atom.
It is the special character of this oxygen-hydrogen bond
that makes water such a good dissolver
O
H
H
Atoms can form a covalent bond
• When 2 atoms get near each other, the protons in
the nucleus of each atom have a certain
attraction for the electrons in the other atom.
• If the attractions are just right, one or more
electrons from each atom can end up moving
around the nuclei of BOTH atoms.
• Even though the atoms in the water molecule
share electrons, the total number of electrons is
still equal to the total number of protons.
Therefore, the water molecule has no overall or
net charge.
The oxygen-hydrogen bond
• Because the oxygen has a greater attraction for electrons than the hydrogens have,
the electrons shared between the oxygen and hydrogen atoms spend more time around
the oxygen than they do around the hydrogens.
• Because electrons have a negative charge, this makes
the area around the oxygen atom slightly negatively charged. It also leaves the
area around the hydrogen atoms slightly positively charged.
- O
H
H
H
O
H
+
BEFORE
+
AFTER
A picture of water
- -
- O
O
H
+
H
H
+
H
+
The charge density model
+
The space-filling model
O
H
H
The ball and stick model
The power of polarity
• The molecules in liquid water associate
very closely with one another
• They orient themselves according to
their polarity (the positive area of one
molecule is attracted to the negative
area of another)
• Attractions between water molecules
are constantly breaking and new ones
are forming with other water molecules
• The attraction water molecules have for
other polar or charged particles is what
makes water so effective at dissolving
many substances
The molecular structure of sucrose
molecules
• Sugar dissolves in water because of the special structure of
the water molecule, but also because of the structure of the
molecules that make up sugar (sucrose).
• C12H22O11
Red = oxygen (slightly negative)
gray = hydrogen (slightly positive)
Dissolution – 2 sucrose molecules
dissolving in water
1
3
2
4
Investigation 1: Scientific questions
and their investigation
Key concepts for students
•
•
•
•
In a scientific experiment, a “variable” is something that can affect the outcome of the experiment.
When designing a scientific experiment, it is necessary to identify and control variables.
In an experiment to find out if a certain variable affects the outcome, only that variable should be
allowed to vary and all other variables should be kept the same.
The temperature of a solvent affects the speed of dissolving.
Learning objectives
Students will be able to:
•
•
•
•
•
Ask scientific questions that they can investigate.
Identify and control variables as they design an experiment to answer the questions.
Be able to make predictions, design and conduct tests, record their observations, and draw logical
conclusions.
Understand the meaning of the “characteristic properties” of an object or substance.
Identify variables that affect dissolving.
Investigation 1: Scientific questions
and their investigation
Investigation questions
What happens when the colored coating of an M&M gets wet?
• What happens when one M&M is placed in water?
• Do some M&M colors dissolve in water faster than others?
• What would the colors look like if we place two or more M&M’s in a
plate of water?
• Is the “line” that forms when two colors meet a special property of
M&M’s?
• Does the temperature of the water affect how fast the colored
coating dissolves from an M&M?
• Does the amount of sugar already dissolved in water affect how fast
an M&M coating dissolves?
Chemistry review: Water
• A water molecule has no overall or “net” charge. It is neutral.
• Because of the way oxygen and hydrogen are bonded together,
water has an area of positive charge and an area of negative charge.
This makes the water a polar molecule.
• Because of water’s polarity, water molecules are attracted to each
other.
• Sugar (sucrose) also has oxygens and hydrogens bonded to each
other. This gives sucrose many areas of positive and negative
charge.
• Water and sucrose are attracted to one another based on the
attractions of opposite charges.
• When the attraction that water molecules have for sucrose
overcomes the attraction sucrose molecules have for each other,
the sucrose dissolves.
• The polar nature of water is what makes water so good at dissolving
many substances.
The structure of water
http://preparatorychemistry.com/water_flash.htm
Ion POGIL
Review - How are ions made from neutral atoms?
metal
metal
Yes
Yes
Yes
Yes
Yes
nonmetal
Yes
Yes
Yes
nonmetal
Yes
Yes
no
no
no
no
2. What distinguishes a neutral atom from an ion?
A change in the number of electrons
3a. Where is the ion charge located in the isotope symbol?
Upper right
3b. Is a charge indicated on the neutral atoms? If yes, where is it located?
There is no charge indicated
4. Which subatomic particle carries a positive charge?
protons
5. Which subatomic particle carries a negative charge?
electrons
6. Propose a mathematical equation to calculate the charge on an ion from the number of
protons and electrons in an ion. Confirm that your equation works using two positive ion
examples and two negative ion examples from model 1
Number of protons – number of electrons = charge
70
38
16
31
Ga 3+
80
35
Br -
31
88
32
80
38
16
35
36
18
50
16
cation
anion
39
cation
anion
8. Could a +3 ion of aluminum be made by adding three protons to an aluminum atom?
No, changing the number of protons would change it into a different element
9. “When you add an electron, you get a positive charge because adding is positive in math.”
a. Explain why this student is incorrect
When you add an electron, you get a negatively charged ion.
b. Provide a better description of how math relates to electrons and ion formation
The electron has a negative charge, so you are adding a negative number
anions
cations
hydrogen
Physical Changes
• Physical change
alters the
substance without
changing its
composition or
chemical identity.
• Boil, melt, cut,
break, split, grind,
crush, bend,
condense, freeze,
dissolve and crack
are examples of
physical changes.
Physical Properties
• A physical property is a condition that
can be measured or observed without
changing the identity of the substance.
Examples of physical properties include
color, solubility, odor, hardness, density,
melting point and boiling point, etc.
Chemical Properties
The ability of a substance to undergo
a chemical reaction to form a new
substance is called a chemical
property. Chemical properties are
observed when a substance
undergoes a chemical change.
Chemical Change
• A change in which one or more
substances are converted into different
substances is called a chemical change
or chemical reaction.
C + O2
CO2
(reactants)
(product)
Look for terms such as . . .
•
•
•
•
•
•
•
•
•
•
•
•
burn
rot
rust
decompose
ferment
explode
oxidize
corrode
grow
precipitate
gas formation
digest
Combustion – powering the space shuttle
Physical Change in Solids
The Chemistry of Solubility
http://www.inquiryinaction.org/chemistryreview/solids/
Dissolving NaCl
http://preparatorychemistry.com/NaCl_flash.htm
Review solutions – solute vs solvent
Investigation 2: Physical properties and
physical change in solids
Key concepts for students
● Solubility is a characteristic property of a substance.
● To measure equal amounts of different solids for a solubility test, it is better to use mass than
volume.
● When comparing solubilities of different solids, all variables should be kept the same except for the
type of solid used.
● The way a substance recrystallizes is a characteristic property of that substance.
● Solubility and recrystallization can be used to help identify an unknown substance.
Learning objectives
Students will be able to:
● Develop an understanding of the meaning of characteristic properties of substances by testing
and comparing different household crystals.
● Recognize that solubility is a characteristic property of a substance.
● Identify an unknown crystal by comparing its characteristic physical properties with those of
four known crystals.
● Measure equal amounts of crystals by mass rather than volume.
● Identify possible variables and suggest ways to control them as they help design valid scientific
investigations.
Investigation 2: Physical properties and
physical change in solids
Investigation questions
• How can you tell if crystals that look the same are really the same
or different?
• Can you identify an unknown crystal by comparing its appearance
to other known crystals?
• Can you identify the unknown crystal by crushing the different
crystals and comparing them?
• Do some of the crystals dissolve more or less than others?
• What is the best way to measure equal amounts of crystals?
• Can you identify the unknown crystal by the amount that dissolves
in water?
• Can you identify the unknown crystal by the way it looks when it
recrystallizes?
Physical Change in Solids - Summary
• Physical change is a change that alters the form or appearance of a material without
changing the chemical composition. One example of a physical change is dissolving.
• Salt is made of ions that are ionically bonded together in a crystal.
•Sugar is made of molecules that are bonded together based on the positively and
negatively charged areas.
• The positive and negative areas of water molecules are attracted to the oppositely
charged ions in salt and to the positive and negative areas on sugar molecules.
• Because salt and sugar are made up of different atoms that bond together differently,
water is attracted to them differently. Water interacts and dissolves salt and sugar in
characteristic ways
• That’s why solids that may look similar behave differently.
Physical Properties and Physical Change in Liquids
http://www.inquiryinaction.org/chemistryreview/liquids/
Investigation 3: Physical properties and
physical change in liquids
Key concepts for students
●Different liquids have different characteristic properties
● A solution made from water and another substance will have characteristics based on the interaction
between water and the other substance.
● The way a liquid behaves on a surface depends on the characteristics of the liquid and the
characteristics of the surface.
● The way a liquid combines with water depends on the characteristics of the liquid and the
characteristics of water.
Learning objectives
● Recognize that different liquids have unique characteristic properties.
● Identify and control variables as they design and conduct tests on each of the liquids.
● Identify unknown liquids based on the results of their tests.
● Understand that the way liquids behave on a surface has to do with the interaction between the
characteristics of the liquid and the characteristics of the surface.
● Understand that the way liquids combine with water has to do with the interaction between the
characteristics of the liquid and the characteristics of water.
Investigation 3: Physical properties and
physical change in liquids
Investigation questions
How can you tell if liquids that look the same are really the
same or different?
● Can you distinguish between four clear colorless liquids
based on the way they look on a brown paper towel?
● How can you identify an unknown liquid based on the way it
behaves on different paper surfaces?
● Can you tell a difference between liquids by the way they
look when they combine with water?
● How can you use the characteristic way each liquid
combines with water to identify the unknown liquids?
Solubility 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?
Relevant National Science Education
Standards:
K–4
Physical science
Properties of objects and materials
Objects have many observable properties
Science as inquiry
Abilities necessary to do scientific inquiry
Ask a question about objects.
Plan and conduct a simple investigation.
Use simple equipment and tools to gather
and extend the senses.
Use data to construct a reasonable
explanation.
Communicate investigations and
explanations.
Understandings about scientific inquiry
Scientific investigations involve asking and
answering a question.
Types of investigations include describing
objects…and doing a fair test.
Good explanations are based on evidence
from investigations
5-8
Physical science
Properties and changes of properties in matter
A substance has characteristic properties
Science as inquiry
Abilities necessary to do scientific inquiry
Identify questions that can be answered through
scientific investigations.
Design and conduct a scientific investigation.
Use appropriate tools and techniques to gather,
analyze, and interpret data.
Develop descriptions, explanations, predictions, and
models using evidence.
Think critically and logically to make the relationships
between evidence and explanations.
Communicate scientific procedures and explanations.
Understandings about scientific inquiry
Different kinds of questions suggest different kinds of
scientific investigations.
Scientific explanations emphasize evidence and have
logically consistent arguments.
Scientific investigations sometimes result in new
ideas and phenomena for study that can lead to
new investigations.
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.