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This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others.
Click to go to website:www.njctl.org
New Jersey Center for Teaching and Learning
Progressive Science Initiative
Slide 2 / 115
PSI 7th Grade Science5-PS1.B : Chemical Reactions5-PS3.A : Definitions of Energy
www.njctl.org
Slide 3 / 115
Table of Contents: Chemical Reactions and Definitions of Energy
Click on the topic to go to that section
· What is a change and what are the signals?
· Physical change versus chemical reaction
· Types of Energy
· Conservation of Mass
· Changes in Energy During a Reaction
· Temperature versus Thermal Energy· Energy Flow· Summary
Slide 4 / 115
Changes and Signals
Return to Tableof Contents
Slide 5 / 115
Chemistry is the study of the properties of matter and how matter
changes.
What does it mean to say that matter changes?
How do you know when matter changes?
Chemistry
Slide 6 / 115
A change is when the properties of a substance are different before
and after something happens.
But how do you know when the properties are different?
Chemical Change
Slide 7 / 115
The easiest way to make observations is with your five senses.
The key is observations.
Observations
Unless you can observe something, you don't have proof that it happened.
Slide 8 / 115
touch
smell
tastesound
sight
SENSES
Slide 9 / 115
Our eyes let us see properties such as
color (Example: red turns green)
shape (Example: rolling chewed gum into a ball)
size (Example: inflating a balloon)
phase - solid, liquid, or gas (Example: ice melting)
and things like light and smoke (Example: logs burning)
Sense of sight
Slide 10 / 115
Our ears do one thing really well,
they hear sounds.
Something must have happened for a sound to be produced.
EXAMPLE: a pair of cymbals being crashed together
Sense of hearing
Slide 11 / 115
Our sense of touch can let us know things such as
texture change : like solid to slimy
(Example: solid hamburger grease melts)
temperature change: warmer or colder
(Example: a glass of water with ice in it)
BE CAREFUL! Unless your teacher tells you it is okay, never
directly touch substances in the laboratory. Some substances are
dangerous and can cause serious injury. Bringing your fingers near
a container like a beaker is close enough to let you know if it is
getting hotter or colder while staying safe.
Sense of touch
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Our taste buds can let us know
how something tastes.
(Example: strawbery ice cream - yum!)
BUT...
NEVER taste anything in the laboratory unless your teacher tells you
to do so, especially if there is another way to get information safely.
Sense of taste
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Our noses let us smell things as they happen in the laboratory.
When a new smell is present, something
must have happened to cause the smell.
(example: rotten banana - yuk!)
Sense of smell
REMEMBER: Always waft chemicals instead of deeply breathing them.
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Sometimes we use tools in the laboratory to help us make
observations, because it is safer or because we get more accurate
information than what our senses alone can provide.
Laboratory Tools
(example: a ruler can measure how long a line is accurately and a thermometer can measure the temperature of boiling water both accurately and safely)
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1 What is always different when a change occurs?
A the substances involved
B at least one property of a substance
C the phases of the substances
Ans
wer
Slide 15 (Answer) / 115
1 What is always different when a change occurs?
A the substances involved
B at least one property of a substance
C the phases of the substances
[This object is a pull tab]
Ans
wer
B
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2 What do you make during an experiment to show whether something is happening or not?
A Observations
B Explanations
C Predictions
Ans
wer
Slide 16 (Answer) / 115
2 What do you make during an experiment to show whether something is happening or not?
A Observations
B Explanations
C Predictions
[This object is a pull tab]
Ans
wer
A
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3 Which of the following are NOT possible to observe with your eyes?
A Color
B Formula
C Size
Ans
wer
Slide 17 (Answer) / 115
3 Which of the following are NOT possible to observe with your eyes?
A Color
B Formula
C Size
[This object is a pull tab]
Ans
wer
B
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4 Which one of your senses should you never use in the laboratory unless your teacher tells you to do so?
A Hearing
B Touch
C Taste
Ans
wer
Slide 18 (Answer) / 115
4 Which one of your senses should you never use in the laboratory unless your teacher tells you to do so?
A Hearing
B Touch
C Taste
[This object is a pull tab]
Ans
wer
C
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5 Which tool is best for helping determine the temperature of a substance?
A Ruler
B Graduated Cylinder
C Thermometer
Ans
wer
Slide 19 (Answer) / 115
5 Which tool is best for helping determine the temperature of a substance?
A Ruler
B Graduated Cylinder
C Thermometer
[This object is a pull tab]
Ans
wer
C
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6 Which tool is best for helping determine the volume of an irregularly shaped object?
A Ruler
B Graduated Cylinder
C Thermometer
Ans
wer
Slide 20 (Answer) / 115
6 Which tool is best for helping determine the volume of an irregularly shaped object?
A Ruler
B Graduated Cylinder
C Thermometer
[This object is a pull tab]
Ans
wer
B
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Physical Change vs Chemical Reaction
Return to Tableof Contents
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What is the difference between a physical change and a chemical reaction?
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A physical change is when a substance changes its properties
without changing what substance it is.
The key idea is that the formula does not change.
physical change
Slide 24 / 115
Phase Changes are Physical Changes
SOLID
LIQUIDGAS
evaporation
condensation
freezingmelting
sublimation
deposition
move the terms to their correct place on the diagram
Slide 25 / 115
Phase Changes are Physical Changes
SOLID
LIQUIDGAS evaporation
condensation
freezingmeltingsublimation
deposition
Slide 26 / 115
A chemical reaction is when a substance changes its properties by
changing what substance it is.
The key idea is that the formula does change.
HO
H
H H
H
H
C CC OO
ethyl alcohol
carbon dioxide
Chemical Reaction
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fire
bubbles
color changes
rust
precipitate
When two solutions mix and a solid forms, the solid is called the precipitate.
Signals of a Chemical Reaction
Slide 28 / 115
Good Science Reminder!
Observations do not prove what happened. They only record what you observed.
It is up to you to explain your observations.
Someone else may explain things differently using your observations. Sometimes further testing is required to get
more information.
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7 Is evaporation a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
Ans
wer
Slide 29 (Answer) / 115
7 Is evaporation a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
A
Slide 30 / 115
8 Is dissolving in water a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either Ans
wer
Slide 30 (Answer) / 115
8 Is dissolving in water a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
A
Slide 31 / 115
9 Is burning paper a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either Ans
wer
Slide 31 (Answer) / 115
9 Is burning paper a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
B
Slide 32 / 115
10 Is baking a cake a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either Ans
wer
Slide 32 (Answer) / 115
10 Is baking a cake a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
B
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11 Are smoke and flame signs of a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either Ans
wer
Slide 33 (Answer) / 115
11 Are smoke and flame signs of a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
B
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12 Are bubbles a sign of a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either Ans
wer
Slide 34 (Answer) / 115
12 Are bubbles a sign of a physical change or a chemical reaction?
A Physical Change
B Chemical Reaction
C May be either
[This object is a pull tab]
Ans
wer
CBubbles can form when something
evaporates, like boiling water.Bubbles can form when chemicals react like vinegar and baking soda.
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Conservation of Mass
Return to Tableof Contents
Slide 36 / 115
When a chemical reaction happens, atoms are not allowed to be
created or destroyed.
conservation of mass
If we start with 4.2g of substances, we must end with 4.2g of substances.
This is known as conservation of mass.
Slide 37 / 115
Conservation of Mass Example #1
150.0g 5.0g
+
Slide 38 / 115
The atoms are also not allowed to change type. If we start with three
carbon atoms and six oxygen atoms, we must end with three carbon
atoms and six oxygen atoms.
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Conservation of Matter
This is known as conservation of matter.
Slide 39 / 115
To make sure that all of the mass and the matter is conserved,
equations need to be balanced. A balanced equation is one that
has the same numbers and types of atoms on both the reactant side
and the product side.
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Balanced Equation
Slide 40 / 115
OO
O
OO
O
C OO
C OO
C OO
C
C C
Reactant Element Product
C
O
Generally, the element symbol is placed in the middle column to
make them easier to track.
In the Reactant and Product columns, the number of atoms of each
element are written. When each element has matching numbers in
both Reactant and Product columns, the equation is balanced.
One of the tools that can help to
balance an equation is called
a REP Table.
REP = Reactant Element Product
To use a REP Table, each element must have a row of its own.
Slide 41 / 115
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Reactant Element Product
C
O
Slide 42 / 115
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Reactant Element Product
3 C
6 O
Slide 43 / 115
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Reactant Element Product
3 C 3
6 O 6
Slide 44 / 115
O
O
O
O
O
O
C OO
C OO
C OO
C
CC
Reactant Element Product
3 C 3
6O
6
3C + 2O3 3CO2
Slide 45 / 115
Reactant Element Product
Fe
O
Fe
O
O
Fe
Fe
O
O
O
Slide 46 / 115
Reactant Element Product
1 Fe
2 O
Fe
O
O
Fe
Fe
O
O
O
Slide 47 / 115
Reactant Element Product
1 Fe 2
2 O 3
Fe
O
O
Fe
Fe
O
O
O
Slide 48 / 115
Reactant Element Product
2 Fe 2
2O
3
Fe
O
O
Fe
Fe
O
O
O
Fe
Slide 49 / 115
Reactant Element Product
2 Fe 4
6 O 6
Fe
O
O
Fe
Fe
O
O
O
Fe
Fe
Fe
O
O
O
OO
O O
Slide 50 / 115
Reactant Element Product
4 Fe 4
6 O 6
Fe
O
O
Fe
Fe
O
O
O
Fe
Fe
Fe
O
O
O
O
O
Fe
Fe
O
O
Slide 51 / 115
C6H12O6 + O2CO2 + H2O
PHOTOSYNTHESIS
Reactant Element Product
C
H
O
Slide 52 / 115
C6H12O6 + O2CO2 + H2O
PHOTOSYNTHESIS
Reactant Element Product
1 C 6
2 H 12
2 + 1 = 3 O 6 + 2 = 8
Slide 53 / 115
C6H12O6 + O2CO2 + 6H2O
PHOTOSYNTHESIS
Reactant Element Product
1 C 6
12 H 12
2 + 6 = 8O
6 + 2 = 8
Slide 54 / 115
C6H12O6 + O26CO2 + 6H2O
PHOTOSYNTHESIS
Reactant Element Product
6 C 6
12 H 12
12 + 6 = 18 O 6 + 2 = 8
Slide 55 / 115
C6H12O6 + 6O26CO2 + 6H2O
PHOTOSYNTHESIS
Reactant Element Product
6 C 6
12 H 12
12 + 6 = 18O
6 + 12 = 18
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13 Which of the following must be followed when balancing chemical equations?
A Conservation of Mass
B Conservation of Matter
C neither
D both
Ans
wer
Slide 56 (Answer) / 115
13 Which of the following must be followed when balancing chemical equations?
A Conservation of Mass
B Conservation of Matter
C neither
D both[This object is a pull tab]
Ans
wer
D
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14 Does the following equation follow Conservation of Mass?
Yes
No
CaBr
C Br
Ans
wer
Slide 57 (Answer) / 115
14 Does the following equation follow Conservation of Mass?
Yes
No
CaBr
C Br
[This object is a pull tab]
Ans
wer
NoCa and C are not the same.
Slide 58 / 115
Ca
Br
Br
BrBr
15 Does the following equation follow Conservation of Mass?
Yes
No
Ca
Ans
wer
Slide 58 (Answer) / 115
Ca
Br
Br
BrBr
15 Does the following equation follow Conservation of Mass?
Yes
No
Ca
[This object is a pull tab]
Ans
wer
Yes
Slide 59 / 115
16 Does the following equation follow Conservation of Mass?
Yes
No
Ans
wer
2Na + Cl2 2NaCl
Slide 59 (Answer) / 115
16 Does the following equation follow Conservation of Mass?
Yes
No
2Na + Cl2 2NaCl[This object is a pull tab]
Ans
wer
Yes
Slide 60 / 115
17 Does the following equation follow Conservation of Mass?
Yes
No Ans
wer
CH3OH + O2 CO2 + H2O
Slide 60 (Answer) / 115
17 Does the following equation follow Conservation of Mass?
Yes
No
CH3OH + O2 CO2 + H2O[This object is a pull tab]
Ans
wer
No
Slide 61 / 115
18 What number should be in front of the H2O to make the equation balanced?
A 1
B 2
C 3
D 4
Ans
wer
H2SO4 + 2NaOH Na2SO4 + ??H2O
Slide 61 (Answer) / 115
18 What number should be in front of the H2O to make the equation balanced?
A 1
B 2
C 3
D 4
H2SO4 + 2NaOH Na2SO4 + ??H2O
[This object is a pull tab]
Ans
wer
B
Slide 62 / 115
Types of Energy
Return to Tableof Contents
Slide 63 / 115
Kinetic energy is energy something has because it is moving.
The bigger the objector the faster it is moving the more kinetic energy it has.
REMEMBER: Molecules and atoms are constantly moving even if you can't see them.
Kinetic energy
Slide 64 / 115
Potential energy is energy that is stored in an object.
Sometimes the energy is stored based on where the object is located. When you lift an object, you store gravitational potential energy. To get the energy back, you would release the object and let it fall.
Potential energy
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Potential energy is energy that is stored in an object.
When you hang something from a spring and the spring stretches, you are storing elastic potential energy. To get the energy back, you would release the object and let the spring return to normal length.
Potential energy
Slide 66 / 115
Electromagnetic energy is the energy of electromagnetic radiation such as sunlight, radio waves, microwaves that is stored in the electric and magnetic fields. This energy can be absorbed by an object.
When energy is stored in chemical substances, it is called chemical potential energy. To release this energy, a chemical reaction must occur.
H
O
OHO
O
Potential energy
Slide 67 / 115
Thermal Energy is the portion of an object's average potential and kinetic energies per atom or molecule, depending on what substance it is. Thermal Energy is responsible for the object having a measurable temperature.
Heat is the energy that is transferred between two
objects that are at different initial temperatures.
Thermal Energy
Slide 68 / 115
REMEMBER: Types of energy are different from sources of energy.
A wind turbine uses the wind as its source of energy. The wind actually has kinetic energy since it is moving that the turbine converts to electromagnetic energy. The faster the wind is moving the more energy the turbine can convert.
Conversion of Energy
Slide 69 / 115
19 Which type of energy is best illustrated by a bee moving very quickly?
A kinetic energy
B chemical potential energy
C electromagnetic energy
Ans
wer
Slide 69 (Answer) / 115
19 Which type of energy is best illustrated by a bee moving very quickly?
A kinetic energy
B chemical potential energy
C electromagnetic energy
[This object is a pull tab]
Ans
wer
A
Slide 70 / 115
20 Which type of energy is best illustrated by calories in food?
A kinetic energy
B chemical potential energy
C electromagnetic energy Ans
wer
Slide 70 (Answer) / 115
20 Which type of energy is best illustrated by calories in food?
A kinetic energy
B chemical potential energy
C electromagnetic energy
[This object is a pull tab]
Ans
wer
B
Slide 71 / 115
21 Which type of energy is best illustrated by a a waterfall being used to turn a turbine?
A kinetic energy
B chemical potential energy
C electromagnetic energy
Ans
wer
Slide 71 (Answer) / 115
21 Which type of energy is best illustrated by a a waterfall being used to turn a turbine?
A kinetic energy
B chemical potential energy
C electromagnetic energy
[This object is a pull tab]
Ans
wer
A
Slide 72 / 115
22 Which type of energy is best illustrated by burning fossil fuels to release energy?
A kinetic energy
B chemical potential energy
C electromagnetic energy Ans
wer
Slide 72 (Answer) / 115
22 Which type of energy is best illustrated by burning fossil fuels to release energy?
A kinetic energy
B chemical potential energy
C electromagnetic energy
[This object is a pull tab]
Ans
wer
B
Slide 73 / 115
23 Which type of energy is transferred between objects that are different temperatures?
A heat
B chemical potential energy
C electromagnetic energy
Ans
wer
Slide 73 (Answer) / 115
23 Which type of energy is transferred between objects that are different temperatures?
A heat
B chemical potential energy
C electromagnetic energy
[This object is a pull tab]
Ans
wer
A
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24 Energy can be created from nothing as part of a chemical reaction.
True
False
Ans
wer
Slide 74 (Answer) / 115
24 Energy can be created from nothing as part of a chemical reaction.
True
False
[This object is a pull tab]
Ans
wer
False.Law of Conservation of Energy
Slide 75 / 115
Energy Changes During Reactions
Return to Tableof Contents
Slide 76 / 115
Conservation of Mass and Conservation of Matter mean that atoms are not allowed to be created or destroyed during a chemical reaction. They are only allowed to change the way they are attached to each other.
What about energy? Is it allowed to change during a chemical reaction?
Chemical Reactions
Slide 77 / 115
Conservation of Energy explains that energy may not be created or destroyed during a chemical reaction. It may be transferred between substances or change its type.
Conservation of Energy
Slide 78 / 115
Endothermic reactions absorb energy from their surroundings. This makes the area around the reaction feel cold.
Making scrambled eggs requires adding energy by heating the pan on the stovetop. That energy transfers into the eggs until
they cook.
Endothermic reactions
Slide 79 / 115
Exothermic reactions release energy to their surroundings. This makes the area around the reaction feel warm or hot.
When using a gas stovetop, the heat energy is released by the natural gas as it burns.
Flames are a good indication that an exothermic reaction is taking place.
Exothermic reactions
Slide 80 / 115
Good Science Reminder!
The system is chosen by the scientist and typically involves the reacting substances.
The surroundings are everything else that isn't part of the system.
The system and surroundings combine to form the universe. Matter, mass, and energy must be constant in the universe
during chemical reactions.
Slide 81 / 115
Energy diagrams are used to visually show if a reaction is endothermic or exothermic. It also can give hints about if the reaction is likely to happen or not.
ENERGY
REACTION COMPLETION
Energy diagrams
Slide 82 / 115
For an endothermic reaction, the energy of the products is higher than the energy of the reactants. Energy was absorbed.
ENERGY
REACTION COMPLETION
reactants
products
Energy diagrams
Slide 83 / 115
For an exothermic reaction, the energy of the products is lower than the energy of the reactants. Energy was released.
ENERGY
REACTION COMPLETION
reactants
products
Energy diagrams
Slide 84 / 115
25 An instant cold pack is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic ReactionA
nsw
er
Slide 84 (Answer) / 115
25 An instant cold pack is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic Reaction
[This object is a pull tab]
Ans
wer
AIt absorbs energy from the
surroundings which makes the surroundings feel colder.
Slide 85 / 115
26 An instant hand warmer is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic Reaction
Ans
wer
Slide 85 (Answer) / 115
26 An instant hand warmer is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic Reaction
[This object is a pull tab]
Ans
wer B
It releases energy to the surroundings (your hands) which makes them surroundings feel
warmer.
Slide 86 / 115
27 Burning oil in a camping lantern is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic Reaction
Ans
wer
Slide 86 (Answer) / 115
27 Burning oil in a camping lantern is an example of what kind of reaction?
A Endothermic Reaction
B Exothermic Reaction
[This object is a pull tab]
Ans
wer B
It releases energy to the surroundings which makes them
surroundings feel warmer and also releases energy in the form of light.
Slide 87 / 115
28 Which reaction pictured is endothermic?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
Ans
wer
Slide 87 (Answer) / 115
28 Which reaction pictured is endothermic?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
[This object is a pull tab]
Ans
wer C
Slide 88 / 115
29 Which reaction pictured is the most exothermic?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
Ans
wer
Slide 88 (Answer) / 115
29 Which reaction pictured is the most exothermic?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
[This object is a pull tab]
Ans
wer A
Slide 89 / 115
30 Which reaction has the products with the most energy?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
Ans
wer
Slide 89 (Answer) / 115
30 Which reaction has the products with the most energy?
A
B
C
ENERGY
REACTION COMPLETION
A
B
C
[This object is a pull tab]
Ans
wer C
Slide 90 / 115
Return to Tableof Contents
Temperature and Thermal Energy
Slide 91 / 115
What is the relationship between temperature and thermal energy?
Why not use temperature instead of energy for the reaction diagrams?
Slide 92 / 115
FROM BEFORE: Thermal Energy is the portion of an object's average potential and kinetic energies per atom or molecule, depending on what substance it is. Thermal Energy is responsible for the object having a measurable temperature.
NEW:Temperature is not energy. It is related to energy but also is influenced by what the substance is and what phase of matter it is. Temperature is something we can directly measure.
Reminder
Slide 93 / 115
Size is not the only thing that influences how much mass an object has. It depends on what the object is made of as well. A soccer ball filled with air will have a different mass than a soccer ball filled with water or a soccer ball filled with cement, even though they are the same size.
SIMILAR SCIENCE
Slide 94 / 115
When making a pizza, sometimes the recipe calls for preheating a pizza stone in the oven. This allows the pizza stone to be the same temperature as the oven.
The air inside the oven also heats up to the temperature of the oven.
When you open the oven, if you touch the pizza stone or the oven itself, you will probably get burned. The air inside the oven doesn't burn you, though. That is because, even though everything in the oven is the same temperature, the air has a lot less thermal energy than the oven or the pizza stone. The interactions of the atoms in each substance cause them to require different amounts of energy.
Slide 95 / 115
Thermal energy also changes when a substance changes phase. If you measure the temperature of ice cream when it melts or of water when it boils, the temperature stays constant until the phase change finishes. Extra energy must be added to make those phase change happen.
Sometimes, objects need to lose energy for a phase change to happen. When water freezes energy must be released before the ice
can form.
Phase Changes
Slide 96 / 115
31 Which has more thermal energy, 5.0g of solid candle wax or 5.0g of liquid candle wax if they have the same temperature?
A the solid wax
B the liquid wax
C they have the same
Ans
wer
Slide 96 (Answer) / 115
31 Which has more thermal energy, 5.0g of solid candle wax or 5.0g of liquid candle wax if they have the same temperature?
A the solid wax
B the liquid wax
C they have the same[This object is a pull tab]
Ans
wer B
Slide 97 / 115
32 Which has more thermal energy, 5.0g of solid candle wax or 15.0g of solid candle wax if they have the same temperature?
A the 5.0g sample
B the 15.0g sample
C they have the same
Ans
wer
Slide 97 (Answer) / 115
32 Which has more thermal energy, 5.0g of solid candle wax or 15.0g of solid candle wax if they have the same temperature?
A the 5.0g sample
B the 15.0g sample
C they have the same[This object is a pull tab]
Ans
wer B
Slide 98 / 115
33 What energy change must happen for a gas to condense to a liquid?
A decrease energy
B increase energy
C more information is needed
Ans
wer
Slide 98 (Answer) / 115
33 What energy change must happen for a gas to condense to a liquid?
A decrease energy
B increase energy
C more information is needed[This object is a pull tab]
Ans
wer A
Slide 99 / 115
34 What energy change must happen for sublimation to occur?
A decrease energy
B increase energy
C more information is needed
Ans
wer
Slide 99 (Answer) / 115
34 What energy change must happen for sublimation to occur?
A decrease energy
B increase energy
C more information is needed[This object is a pull tab]
Ans
wer B
Slide 100 / 115
35 If substance one and substance two are at the same temperature, which one has more thermal energy?
A substance one
B substance two
C more information is needed
Ans
wer
D they have the same energy
Slide 100 (Answer) / 115
35 If substance one and substance two are at the same temperature, which one has more thermal energy?
A substance one
B substance two
C more information is needed
D they have the same energy
[This object is a pull tab]
Ans
wer C
If you don't know the amount of each substance or what the substances
are, you can't compare their thermal energies even if you know their
temperatures.
Slide 101 / 115
36 If 150g of iron skillet and 150g of water are both at 100 degrees Celsius, which has more thermal energy, the iron or the water?
A the iron skillet
B the water
C more information is needed
Ans
wer
D they have the same energy
Slide 101 (Answer) / 115
36 If 150g of iron skillet and 150g of water are both at 100 degrees Celsius, which has more thermal energy, the iron or the water?
A the iron skillet
B the water
C more information is needed
D they have the same energy[This object is a pull tab]
Ans
wer
BIt usually only takes a few moments to heat up a skillet on a stovetop but can take several minutes to get the
water to boil.
The official science is that water has a higher specific heat than iron.
Slide 102 / 115
Energy Flow
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Slide 103 / 115
If two objects can have the same amount of thermal energy but different temperatures, or different thermal energies and the same temperature, when does energy transfer between them?
Slide 104 / 115
When two substances touch, if they have different temperatures, energy will flow from the hotter substance to the colder substance until their temperatures are the same.
Once the temperatures are the same, the energy transfer process stops.
Slide 105 / 115
In science, unless you are talking about a disease, "cold" is an adjective, not a noun. Heat is the energy that transfers between objects.
Ice doesn't transfer cold to the juice in the glass. The juice actually transfers energy to the ice. The juice makes the ice warmer until it melts.
Slide 106 / 115
37 What quantity tries to balance out when energy is transferred via heat?
A thermal energy
B temperature
C they both must be the same
Ans
wer
Slide 106 (Answer) / 115
37 What quantity tries to balance out when energy is transferred via heat?
A thermal energy
B temperature
C they both must be the same[This object is a pull tab]
Ans
wer B
Slide 107 / 115
38 Which direction does heat flow?
A higher temperature to lower temperature
B lower temperature to higher temperature
C higher thermal energy to lower thermal energy
Ans
wer
Slide 107 (Answer) / 115
38 Which direction does heat flow?
A higher temperature to lower temperature
B lower temperature to higher temperature
C higher thermal energy to lower thermal energy[This object is a pull tab]
Ans
wer
A
Slide 108 / 115
39 Which of the following best describes how energy transfers when you cook an egg in a skillet on a stovetop?
A the stovetop transfers energy to the egg
B the egg absorbs energy from the stovetop
C the egg absorbs energy from the skillet
Ans
wer
Slide 108 (Answer) / 115
39 Which of the following best describes how energy transfers when you cook an egg in a skillet on a stovetop?
A the stovetop transfers energy to the egg
B the egg absorbs energy from the stovetop
C the egg absorbs energy from the skillet[This object is a pull tab]
Ans
wer
C
Slide 109 / 115
40 Which of the following best describes why energy transfers when you cook an egg in a skillet on a stovetop?
A the stovetop has a higher temperature than the egg
B the skillet has a lower temperature than the egg
C the egg has a lower temperature than the skillet
Ans
wer
Slide 109 (Answer) / 115
40 Which of the following best describes why energy transfers when you cook an egg in a skillet on a stovetop?
A the stovetop has a higher temperature than the egg
B the skillet has a lower temperature than the egg
C the egg has a lower temperature than the skillet
[This object is a pull tab]
Ans
wer
C
Slide 110 / 115
41 If object one is the same temperature as object two but has twice as much thermal energy, what happens when the objects touch?
A object one warms object two
B no energy is transferred
C object one gives energy to object two
Ans
wer
Slide 110 (Answer) / 115
41 If object one is the same temperature as object two but has twice as much thermal energy, what happens when the objects touch?
A object one warms object two
B no energy is transferred
C object one gives energy to object two[This object is a pull tab]
Ans
wer
B
Slide 111 / 115
42 If object one is the same temperature as object two but has twice as much mass, what happens when the objects touch?
A object one warms object two
B no energy is transferred
C object one gives energy to object two
Ans
wer
Slide 111 (Answer) / 115
42 If object one is the same temperature as object two but has twice as much mass, what happens when the objects touch?
A object one warms object two
B no energy is transferred
C object one gives energy to object two[This object is a pull tab]
Ans
wer
B
Slide 112 / 115
Summary
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Slide 113 / 115
· When a substance has different properties before and after something happens, a change has taken place.
· Observable changes can be either physical changes where the substance does not change its formula or chemical reactions where the substance changes into a new substance with a new formula.
· When changes occur, mass and matter must be conserved and may not change.
Slide 114 / 115
· A balanced equation shows the correct ratios of reactants and products that allow mass and matter to be conserved.
· There are several types of energy such as kinetic, chemical potential, and thermal.
· Energy may be absorbed or released during a chemical reaction.
· Thermal energy is different from temperature.
· Energy flows from higher temperature to lower temperature.
Slide 115 / 115
