Transcript File

End of Year Review
Scientific Method and
Properties of Matter and
Chemistry
Wake County
8th Grade
Science Curriculum
Essential Question
#79
•How do I set up
an experiment?
Lab Safety
What are the
potential
hazards?
• Broken glass
• Spills
• Fire
• Electrical
shocks
• Can you think
of other
hazards?
Essential Question
#80
• How do I safely
manipulate materials and
equipment?
Lab Safety
How do I safely
manipulate materials
and equipment and
conduct appropriate
procedures?
• Follow safety
rules covered at
the beginning of
the year.
• Know these
rules!
• Follow teacher
instructions.
• What else
applies?
Essential Question #80
• How do I safely manipulate
materials and equipment?
• Know all the safety rules of the
safety contract and classroom.
Essential Question #81
•How do I conduct
appropriate
procedures?
Scientific Method
•
•
•
•
Ask a Question
Do Background Research
Construct a Hypothesis
Test Your Hypothesis by Doing
an Experiment
• Analyze Your Data and Draw a
Conclusion
• Communicate Your Results
Essential Question #81
• How do I conduct
appropriate procedures?
• Know and use the
Scientific Method.
Essential Question
•What types of
questions can be
answered through
scientific
investigation?
Scientific Method
• Identify and create
• What types of
questions can
be answered
through
scientific
investigations?
• How do I set
up an
experiment?
questions and
hypotheses that
can be answered
through scientific
investigations.
• Data must be
measurable.
• Understand
appropriate
experimental
procedures. Can you
give some examples?
Essential Question #82
• What types of questions can be
answered through scientific
investigation?
• Questions must be testable and
measurable.
• No opinion can be used as data.
Analyzing Data
How do you
analyze large
amounts of
data?
•
•
•
•
Line Graph
Bar Graph
Pie Chart
Can you think of
other ways to
analyze data?
Essential Question
#83
•What are dependent
and independent
variables and how
are they related?
Analyzing Data
What are dependent
and independent
variables and how
are they related?
Dependent
variable
Independent variable
• Independent variable
is the variable being
tested. Can be
changed to get
different
observations. Always
the X axis
• Dependent variable
results depend on the
independent variable.
Changes based on
changes in the
independent variable.
Always the Y axis.
Essential Question
#83
•What are dependent
and independent
variables and how
are they related?
•Can you explain?
Essential Question
#84
•Why do I need
a control?
Scientific Method
• Controls are not
• Why do I need affected by the
to have a
independent variable.
control?
• Gives data
unaffected by the
variable being tested.
• You need to know
what would happen if
nothing was done to
the subject being
tested
Essential Question
#84
• Why do I need a control?
• You need to know what
the results would be
without the variable
being tested.
Essential Question
#85
•How many
variables do I
manipulate or
change?
Experimentation
How many
variables do
I manipulate
(or change)?
Always
Only ONE
Essential Question
#85
• How many variables do I
manipulate or change?
• Just one or you don’t know
which one provided the
measurable data.
Essential Question
#79
•How do I set up
an experiment?
•Class discussion
Properties of Matter
Matter
Mass
Has mass and volume
Amount of matter contained in a
substance
Measured in grams (g)
Volume
Amount of space an object
occupies
Measured in liters (L)
Changes in Matter
Physical
Change
• A change in a substance
that doesn’t change it’s
identity
• Example: Ice melting or
chopping wood
Chemical
Change
• A change in which one
or more substances
combine or break apart
to form new substances
• Example: burning paper
or putting an acid in a
base
Essential Question
#86
• How is density
used to compare
different
substances?
Properties of Matter
• Density is the quantity
How is density used
of matter that is packed
to compare
into a fixed space.
different
• D = m/v (OR) gram/liter
substances?
• Density = Mass/Volume
• Density > 1 (sinks)
• Density < 1 (floats)
• Buoyancy – the ability
of a fluid to exert an
upward force on an
object that is immersed
in the fluid
Essential Question
#86
• How is density used to
compare different
substances?
• Density is different for every
material. If you know a
materials density, it may
help identify the material.
Essential Question
#87
• How are boiling
points and melting
points used to
compare different
substances?
Properties of Matter
In matter, how
does
temperature
change?
• All atoms and
molecules move.
• The faster they
move, the higher
the temperature
• Change in
temperature occurs
by speeding up or
slowing down
particle movement
States of Matter
Gases
• Occur when particles move freely
(are fluid)
• Volume changes by being easily
compressed or expanded
• A gas maintains the shape of its
container
• If these particles are heated, they
move faster and need more space.
This is why heat expands volume
and decreases density.
• Created when substances boil or
evaporate.
• If the particles slow down, they
can become a liquid.
(condensation)
States• of
Matter
Occur when particles move
Liquids
•
•
•
•
freely (fluid) but are bonded to
each other.
Volume is constant but shape
changes
Movement is slower than that of
gases.
If these particles are heated,
they easily escape and become
gas. (evaporation or boiling)
If they slow down, they easily
get trapped in place and become
a solid. (freezing)
States of Matter
Solids
• Occur when particles vibrate
in place
• Have a definite shape and
volume
• Different substances have
different freezing points.
• Water becomes solid at 0C if
heat is taken away. This is
freezing.
• Iron becomes solid at 1538°C if
heat is taken away. This is
also freezing.
Of the states of matter,
gas is the only state
that
A.Is fluid
B.Has mass
C.Is highly compressible
D.Has a definite shape
Of the states of matter,
gas is the only state
that
A.Is fluid
B.Has mass
C.Is highly compressible
D.Has a definite shape
States of Matter
Terms to Remember
• Liquid is changed into a
vapor.
• Liquid is changed into a
• Boiling
vapor by adding heat
• Condensation • Gas cooling and
becoming liquid
• Liquid cooling and
• Freezing
becoming a solid
• Solid turning directly into
• Sublimation
a gas without becoming
liquid (example: dry ice)
• Evaporation
Properties of Matter
• Different substances
• How are
have different
boiling/melting
boiling/melting points.
points used to
• 0C is the melting and
compare
freezing point of
different
water.
substances?
• 100C is the boiling
point of water.
• Substances in water
can change the
boiling/melting points
Essential Question
#87
• How are boiling points and melting
points used to compare different
substances?
• If you can find the boiling and
melting point of a substance, the
information may help you identify
that substance. All materials have
consistent boiling and melting
points.
Essential Question
(#77)
• How does water hold
heat?
(We already answered,
but lets review again)
Properties of Matter
Specific Heat
• The amount of
energy needed to
raise one gram of a
substance by one
degree Celsius
• Water has a very
high specific heat
• This means it can
absorb a lot of heat
• That is why water
works well to put out
a fire
Essential Question (#77)
• How does water hold heat?
• Because of the strength of
hydrogen bonds, water will
hold a lot of heat.
• Since there is so much
water on Earth, it helps keep
our climates from going to
extreme temperatures.
Which of the following has the
least effect on lake water
temperature?
A. The depth of the water
B. The angle of incoming sun
rays
C. The number of fish in the lake
D. The lake’s surface area
Which of the following has the
least effect on lake water
temperature?
A. The depth of the water
B. The angle of incoming sun
rays
C. The number of fish in the lake
D. The lake’s surface area
Essential Question
#88
• How is solubility
used to compare
different substances?
Properties of Matter
What is a
solution?
What is a solvent?
What is a solute?
What is a saturated
solution?
A mixture formed
when one substance
dissolves another.
A substance that dissolves
another substance
A substance that is
dissolved by the solvent.
Saturated:
has as
much solute as a
solvent can hold
Properties of Matter
How is
• Is the substance a
solubility used solvent?
• Is the substance a
to compare
solute?
different
• Does it dissolve in water?
substances?
• Does it dissolve in oil?
• What else do you know
about solubility?
• Insoluble means that
some substances are not
soluble
Essential Question
#88
• How is solubility used to
compare different substances?
• If you find what will dissolve a
substance and how fast it
dissolves, it can help you
identify the substance. All
substances have unique
dissolving qualities.
Properties of Matter
How can
temperature affect • Remember, heat is the
movement or vibration
the speed a
of atoms and
solute will
molecules.
dissolve in a
• Rapid movement of
solvent?
the particles of the
solvent will speed up
the rate of the solute
breaking up
(dissolving).
Properties of Matter
Chromatography
: a means of
separating a
mixture based on
polarity and
solubility
upload.wikimedia.org
www.membrane-solutions.com
Chromatography of
chlorophyll
Chromatography of inks
Essential Question
#89
• How is malleability
used to compare
different substances?
Essential Question
#90
• Which material is the
most/least
malleable?
Properties of Matter
How is
malleability
used to compare
different
substances?
• Malleability is the
ability to be
hammered into a
sheet.
• Metals are more
malleable.
• Can you give an
example of a
substance that is
malleable?
Essential Question
#89
• How is malleability used to
compare different substances?
• A substance is malleable or not.
Some substances are more
malleable than others. If a
substance is malleable, you
know it is probably a metal.
Essential Question #90
• Which material is the
most/least malleable?
• Metals are the most
malleable
• Nonmetals are the
least malleable.
Essential Question
#91
•How is ductility
used to compare
different
substances?
Properties of Matter
• Ductility - the ability
to be stretched into
a thin wire
• Some substances
are more ductile
than others.
• Can you give an
example of a
substance that is
ductile?
Essential Question
#91
• How is ductility used to
compare different
substances?
•Ductility - the ability to be
stretched into a thin wire
•Some substances are
more ductile than others.
Chemistry
57
Essential Question
#92
• What is the structure
of an atom?
Chemistry
Atom: the smallest unit of matter that
retains the identity of the substance
Three particles:
1. Protons
2. Neutrons

Nucleus
3. Electrons
alternativealtruist.wordpress.com
59
Chemistry
Structure of an Atom
•Nucleus: contains protons and neutrons; the
total number of particles in the nucleus is the
atomic mass number
•Proton: subatomic particle with a positive
charge and located in the nucleus of the atom.
The number of protons gives the atom its
identity (atomic number)
•Neutron: subatomic particle with no charge,
the same mass as a proton, and located in the
nucleus of the atom
60
Chemistry
Structure of an Atom
The structure of an hydrogen atom, helium
atom, lithium atom and a sodium atom
www.chemicalconnection.org.uk
61
Chemistry
Structure of an Atom
Electron: subatomic particle with a
negative charge and located outside the
nucleus
commons.wikimedia.org
commons.wikimedia.org
en.wikipedia.org
62
Structure of an Atom
Where do you find the number of
particles of atoms in a periodic
table?
kaffee.50webs.com
63
Chemistry
Structure of an Atom
Atomic Number
The number of protons in the nucleus of an atom
This number identifies the atom
Increases as you go to the right in periods and starts again
on the left of the next period
Atomic Number = Protons
1
2
3
11
www.chemicalconnection.org.uk
64
Chemistry
Structure of an Atom
Atomic Mass Number:
the number of protons
and neutrons in the nucleus of an atom
As the atomic number increases, usually, so does the mass
As the atomic number increases, usually, so does the density
mass number = protons + neutrons
The number of neutrons depends on which isotope
of the element you are using.
Atomic Mass Numbers
H-1
for the isotopes of hydrogen
H-2
H-3
65
Chemistry
Structure of an Atom
Atomic Mass: the average mass number
of all isotopes of an atom. Round this
number to find the mass number of the
atom.
en.wikiversity.org
education.jlab.org
Most hydrogen atoms have only a proton
(protium). But since there are two isotopes
of hydrogen, (deuterium and tritium) the
atomic mass is a little more than one. →
66
Chemistry
Structure of an Atom
To find the numbers of the
different particles of an element:
Atomic Number = Protons
atomic number 6 = 6 protons
Electrons = Protons
6 electrons = 6 protons
iss.cet.edu
Atomic Mass – Protons = Neutrons
atomic mass (rounded) 12 – 6 protons = 6 neutrons
67
Essential Question
#92
• What is the structure of an
atom?
• Protons (+) and Neutrons
(o) inside nucleus
• Electrons (-) surrounding
the nucleus
Looking at the block of the element
Carbon on the periodic table, the
number 6 represents?
A.
C.
D.
Atomic mass of the element carbon
B. Atomic number of the element
carbon
Number of neutrons in the element
carbon
Number of valence electrons in the
element carbon
69
Looking at the block of the element
Carbon on the periodic table, the
number 6 represents?
A.
C.
D.
Atomic mass of the element carbon
B. Atomic number of the element
carbon
Number of neutrons in the element
carbon
Number of valence electrons in the
element carbon
70
Essential Question
#93
• What are chemicals?
Chemistry
What is a chemical?
Chemical: any substance made of atoms
Element: a substance that cannot be broken
down into simpler substances by ordinary
chemicals means
Periodic Table: an arrangement of elements in
order of increasing atomic numbers that
demonstrates the periodic patterns that occur
among the elements
72
Essential Question
#93
• What are chemicals?
• Anything that is
made of atoms.
• You are made of
chemicals.
Because zinc can combine with
other substances but cannot be
changed into a simpler
substance by an ordinary
chemical process, zinc is
classified as A. A compound
B. A mixture
C. An element
D. An acid
Because zinc can combine with
other substances but cannot be
changed into a simpler
substance by an ordinary
chemical process, zinc is
classified as A. A compound
B. A mixture
C. An element
D. An acid
Essential Question
#94
• How are the
elements categorized
in the periodic table?
Essential Question
#95
• What happens to the
number of protons as
you move to the right
on a periodic table?
Essential Question
#96
• Which material is the
most/least dense?
Remember:
Atomic Number = Number of Protons
Atomic Numbers increase as they
move across the periodic table from
left to right.
Atomic mass affects density.
The greater the atomic mass, the
greater the density.
facstaff.gpc.edu
80
Essential Question
#95
• What happens to the number
of protons as you move to
the right on a periodic table?
• The number of protons, like
the atomic number,
increases as they move from
left to right.
Essential Question #96
• Which material is the
most/least dense?
• Hydrogen is the least dense
of all elements with an
atomic mass of one.
• As the elements go from left
to right in the periods,
atomic mass increases so
density does also.
Structure of the Periodic
Table
Period: elements that occur in a
horizontal row on the periodic table;
there are eight periods
group or family
→
period→
energy.com
Group or Family: elements that occur in a
vertical column on the periodic table;
there are eighteen groups
83
Essential Question
#97
• How does the
periodic table help
you to identify the
properties of the
elements?
Alkali Metals
www.learner.org
•First column in the
periodic table
•They have one
electron in the outer
shell
•This characteristic
makes them the most
reactive metals
85
www.learner.org
Alkaline Earth Metals
•Second column in the periodic table
•Have two electrons in the outer shell
•Second most reactive metals in the periodic
table
www.learner.org
86
Essential Question
#98
• Which materials
provide the
best/worst electrical
conductivity?
Essential Question
#99
• Which material is the
most/least magnetic?
Metals
An element below and to the left of the stair-step line of
metalloids
About 80% of the known elements are metals
Most are shiny and conduct heat and electricity
Malleable
Low specific heat (absorbs heat quickly)
Many metals demonstrate magnetism
Are pink in the chart
media-2.web.britannica.com
89
A mixture of iron filings and
sulfur can easily be separated
by A.
Placing the mixture in water.
B. Performing a chemical
reaction.
C. Heating the mixture.
D. Using a magnet.
90
A mixture of iron filings and
sulfur can easily be separated
by A.
Placing the mixture in water.
B. Performing a chemical
reaction.
C. Heating the mixture.
D. Using a magnet.
91
Which best describes why metals
are used for making pots and
pans that are used for cooking?
A. Metals have low specific heats
and high melting points.
B. Metals have high specific heats
and low melting points.
C.Metals have low specific heats
and low melting points.
D.Metals have high specific heats
and high melting points.
92
Which best describes why metals
are used for making pots and
pans that are used for cooking?
A. Metals have low specific heats
and high melting points.
B. Metals have high specific heats
and low melting points.
C.Metals have low specific heats
and low melting points.
D.Metals have high specific heats
and high melting points.
93
Which property of metals
allows them to be used to
make coins that have the
same thickness?
A.Electrical conductivity
B.Density
C.Malleability
D.Specific heat
94
Which property of metals
allows them to be used to
make coins that have the
same thickness?
A.Electrical conductivity
B.Density
C.Malleability
D.Specific heat
95
Metalloids
An element with properties of both metals and
nonmetals located along the stair-step line on the right
side of the periodic table
Most of the elements touching the stair-step line
Green in the chart
media-2.web.britannica.com
96
Nonmetals
An element above and to the right of the stair-step line of
metalloids
Dull
Non-conductive of heat or electricity so they make good
insulators
Non malleable
Blue in the chart
Non magnetic
media-2.web.britannica.com
97
Essential Question
#98
• Which materials provide the
best/worst electrical
conductivity?
• Metals are the best
conductors
• Nonmetals are the worst
conductors
Essential Question #99
• Which material is the
most/least magnetic?
• Metals are the most
magnetic
• Nonmetals are the
least magnetic.
Insulation materials reduce heat
loss because they Are poor conductors
B. Block out the sun
C. Reduce evaporation
D. Promote convection
A.
100
Insulation materials reduce heat
loss because they Are poor conductors
B. Block out the sun
C. Reduce evaporation
D. Promote convection
A.
101
Halogens
•Seventeenth column in the periodic table (next
to last)
•Needs one electron to fill the outer shell
•Most reactive nonmetals in the periodic table
www.learner.org
102
Noble Gases
• Full outer shells
• The least reactive of all elements
• Eighteenth column (last group)
www.learner.org
103
Essential Question
#97
• How does the periodic table
help you to identify the
properties of the elements?
• Due to the arrangement of the
outer electrons, elements in the
same group or family have
similar characteristics.
Essential Question #94
• How are the elements categorized in
the periodic table?
• Groups or families and periods
• Metals, nonmetals, and metalloids
• Alkali metals
• Alkaline earth metals
• Transition metals
• Halogens
• Nobel gases
Essential Question
#100
• In a chemical or
physical change, how
does volume change?
Changes in Matter
Physical Change


Chemical
Change



A change in a substance that
doesn’t change it’s identity
Example: Ice melting or
chopping wood
A change in which one or more
substances combine or break
apart to form new substances
Example: burning paper or
putting an acid in a base
Bonds are broken and/or made
in a chemical change (reaction)
107
Changes in Matter
Physical Change
In a physical change, no
change in volume occurs in
solids and liquids. Gases
however can expand when
heated.
Chemical
Change
In a chemical change, if the
new products created are
more or less dense than the
reactants before the reaction,
there is a change in volume.
An example is when a log
burns, the gases given off
have a greater volume than the
original wood.
Essential Question
#100
• In a chemical or
physical change, how
does volume change?
• Class discussion
Which best describes the physical
change of an aluminum soda can
after it is crushed?
There is a change in the mass of the
can.
B. There is a change in the weight of the
can.
C. There is a change in the volume of
the can.
D. There is a change in the specific heat
of the can.
A.
110
Which best describes the physical
change of an aluminum soda can
after it is crushed?
There is a change in the mass of the
can.
B. There is a change in the weight of the
can.
C. There is a change in the volume of
the can.
D. There is a change in the specific heat
of the can.
A.
111
Which process is a physical
change?
Rusting iron
B. Burning coal
C. Tarnishing silver
D. Melting ice
A.
112
Which process is a physical
change?
Rusting iron
B. Burning coal
C. Tarnishing silver
D. Melting ice
A.
113
Essential Question
#101
• How do elements
combine to produce
compounds?
Essential Question
#102
• Which element is
found in all living or
once living things?
ESSENTIAL QUESTION
#103
•Which materials are
the most/least
soluble?
Chemical Bonding
Two Kinds
1. Ionic Bonding
- formed when two or more atoms gain or lose
electrons and then become charged
Since ions are
charged particles,
they are also easily
dissolved in water
ffdgfg
www.es.ucsc.edu
117
ESSENTIAL QUESTION
#103
• Which materials are the
most/least soluble?
• Ions are the most soluble.
• All other non-charged
atoms are the least
soluble.
Chemical Bonding
Two Kinds
2. Covalent Bonding
- formed when two or more atoms share
electrons
www.school-for-champions.com
119
Chemical Bonding
• Elements combine to make
compounds
• Example:
1. O (oxygen) + 2H (two
hydrogen)  H2O (one water
molecule) Covalent Bonding
2. Na (sodium) + Cl (chlorine) 
NaCl (salt) Ionic Bonding
120
Essential Question
#101
• How do elements combine to
produce compounds?
• Ionic bonding which
involves gaining and losing
electrons.
• Covalent bonding which
involves sharing electrons.
You are a carbon based
life form
•This means all of your cells
contain carbon.
•The four types of molecules that
make up your body contain
carbon.
•These are sugars, lipids (fats),
proteins, and nucleic acids.
Essential Question
#102
• Which element is
found in all living or
once living things?
• Carbon
Essential Question
#104
• In a chemical or
physical change, how
is a gas produced?
Essential Question
#105
• During a normal
chemical reaction,
what happens to
matter?
Chemical Reaction
• Occurs when the original substance(s)
change form into new substance(s)
• Substances change due to changes in
bonds or changes in bonds create new
substances
• Some clues to a chemical reaction
may include bubbles, smoke, a strong
smell, color change, temperature
change, or a sizzling sound
• Example: two liquids mixed together
create a gas.
126
Changes in Matter
Physical Change
In the physical change of
vaporization, boiling and
evaporation, gases are
formed from liquids.
Chemical
Change
In a chemical change, a
reaction can lead a set of
reactants to form a gas
as a product.
Essential Question
#104
• In a chemical or physical
change, how is a gas
produced?
• Can both produce gas?
• Yes! A chemical
reaction can produce a
gas.
Essential Question
#105
• During a normal chemical
reaction, what happens
to matter?
• Reactants break or make
bonds to form new
products or substances.
Which is evidence that
elements can combine to
form new compounds?
A.Melting a solid
B.Freezing a liquid
C.Moving a piece of metal
with a magnet
D.Pouring two liquids
together to create a solid
130
Which is evidence that
elements can combine to
form new compounds?
A.Melting a solid
B.Freezing a liquid
C.Moving a piece of metal
with a magnet
D.Pouring two liquids
together to create a solid
131
Essential Question
#106
• In a chemical or
physical change, how
does mass change?
Essential Question
#107
• During a chemical
reaction, how does the
total mass of the products
compare to the total mass
of the reactants?
Law of Conservation
of Mass
In a chemical reaction, matter
cannot be either created or
destroyed but changes form.
• Example: When wood is burned, it isn’t
destroyed but changed into ash, gases
(smoke), water vapor (steam in the
smoke), and energy (heat)
• All chemical equations have to show
the same number of atoms on each
side to show that no atoms are lost.
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Chemical Reaction
6CO2 + 6H2O  C6H12O6 + 6O2
reactants
___
6
18
O ___
12
H ___
C
products
___
6
18
O ___
12
H ___
C
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• In a physical change, mass does
not change. No matter what
physical changes occur, all
atoms and molecules stay the
same, therefore the mass stays
the same.
Essential Question
#106
• In a chemical or physical
change, how does mass
change?
• Mass is never lost or
gained but changes form.
Essential Question
#107
• During a chemical reaction,
how does the total mass of
the products compare to
the total mass of the
reactants?
• The mass of the products is
equal to the mass of the
reactants.
A chemical reaction produces two
new substances, and each
product has a total of 25
grams. What was the total
mass of the reactants?
25 grams
B. 50 grams
C. 75 grams
D. 100 grams
A.
139
A chemical reaction produces two
new substances, and each
product has a total of 25
grams. What was the total
mass of the reactants?
25 grams
B. 50 grams
C. 75 grams
D. 100 grams
A.
140
Chemical Reaction
Photosynthesis
Coefficient

6CO
2 + 6H2O  C6H12O6 + 6O2
reactants
products

 is a symbol that means “yields”
Subscript
Coefficient: number in front of a formula that
multiplies all atoms in the formula to the right
Subscript: number that only multiplies the element
to its left
You start with carbon dioxide and water and
end up with sugar and oxygen
Count the number of carbon, hydrogen, and oxygen atoms on
both sides. They must be equal according to the Law of
Conservation of Mass.
141
In the chemical formula for ammonia, NH3,
what does the subscript 3 represent?
A.
B.
C.
D.
The number of nitrogen and hydrogen
atoms in each molecule of ammonia.
The number of hydrogen atoms in each
molecule of ammonia.
The number of ammonia molecules that
will bond together.
The number of nitrogen atoms in each
molecule of ammonia.
142
In the chemical formula for ammonia, NH3,
what does the subscript 3 represent?
A.
B.
C.
D.
The number of nitrogen and hydrogen
atoms in each molecule of ammonia.
The number of hydrogen atoms in each
molecule of ammonia.
The number of ammonia molecules that
will bond together.
The number of nitrogen atoms in each
molecule of ammonia.
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Essential Question
#108
• In a chemical or
physical change, how
does temperature
change?
Energy in Chemical
Reactions
Endothermic reaction: a chemical
reaction in which heat is taken in;
any acid; base reaction takes in heat;
the beaker feels cold after the
reaction.
Exothermic reaction: a chemical
reaction in which heat is given off;
fire is an exothermic reaction
Energy in Physical
Changes
• Temperature can change in physical
changes also.
• When melting or vaporizing, molecules
absorb heat. That is why these changes of
state occur more when it is warm.
• When condensing or freezing, molecules
give off heat. That is why you have to
remove the heat to get materials to go
through these changes of state.
Essential Question
#108
• In a chemical or physical
change, how does
temperature change?
• Both chemical and physical
changes can cause
temperature changes.
Energy Transformations
Energy can change forms
• Light can change into heat: sunlight feeling hot
• Chemical energy can become mechanical
energy: cells using sugar for energy
• Chemical energy can become heat: wood
burning
• Heat can be changed into mechanical energy:
steam boat
• Light can be changed into chemical energy:
photosynthesis
• Electricity can be changed into heat: oven
• Electricity can be changed into mechanical
energy: fan
148
Which of the following could
best be used to demonstrate
energy being transformed from
electricity to heat?
A magnifying glass
A triple beam balance
C. A toaster
D. A gas oven
A.
B.
149
Which of the following could
best be used to demonstrate
energy being transformed from
electricity to heat?
A magnifying glass
A triple beam balance
C. A toaster
D. A gas oven
A.
B.
150
A burning candle is in the process
of transforming Heat energy into chemical
energy.
B. Chemical energy into light and
heat.
C. Chemical energy into
mechanical energy.
D. Chemical energy into nuclear
energy.
A.
151
A burning candle is in the process
of transforming Heat energy into chemical
energy.
B. Chemical energy into light and
heat.
C. Chemical energy into
mechanical energy.
D. Chemical energy into nuclear
energy.
A.
152
Chemical Reaction
Acids and bases are chemically opposite
Acids contain many H+ and Bases contain many OHBASE
ACID
NEUTRAL SUBSTANCES
NaOH + HCL →NaCl + H2O
sodium hydroxide
hydrochloric acid
salt
water
www.livinglandscapes.bc.ca
153
When a base is mixed with an
acidic solution, neutralization
occurs because the Base reaches absolute zero
B. Acid evaporates
C. Base chemically reacts with the
acid
D. Mass of the solution increases
A.
When a base is mixed with an
acidic solution, neutralization
occurs because the Base reaches absolute zero
B. Acid evaporates
C. Base chemically reacts with the
acid
D. Mass of the solution increases
A.
155
Mixtures
•The physical combination of 2 or
more substances
•Can be separated by physical means
•A solution is a liquid mixture
•Example: sand mixed with sugar
can be separated by adding water,
pouring off the liquid, evaporating the
water so the sugar is left behind
156
Mixtures
Homogeneous mixture:
a mixture that is evenly
mixed; also called a
solution; milk is
homogenized
gallonchallenge.org
Heterogeneous mixture:
a mixture that is unevenly
mixed; soil is an example
nesoil.com
157