Download Unit 8.1.3 Study Guide: Energy in Changes

Name__________________________________________ Per.________
Unit 8.1.3 Study Guide: Energy in Changes
I Can Statements
“I Can Statements” are the learning targets for each unit. By the time you take the test for this unit,
you should be able to confidently say:
1. I can identify the different forms of energy given off in a chemical change.
2. I can explain how molecules are affected when heat is added or taken away.
3. I can measure, graph, and explain the relationship between the states of water and changes
in its temperature.
4. I can explain how adding or removing heat affects a change.
5. I can show that other variables (e.g. stirring, crushing, and concentration) affect the speed of
changes.
Teach the Concepts
One great way to study is to explain concepts to others. Teach the following concepts to a parent,
grandparent, aunt, uncle, or even an older sibling.
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What happens to molecules when energy is added?
What happens to molecules when energy is taken away?
How does energy affect a chemical change or reaction?
How do molecules behave in each phase (solid, liquid, and gas)?
What is the difference between an exothermic and endothermic reaction?
What are some of the types of energy transformations?
Describe exactly what is happening at every part of the phase change graph of water, going
both up AND down in energy.
Signature _______________________________
Read/Summarize
Energy is involved in chemical and physical changes. Energy is the ability to do work. In fact, your
car uses chemical energy to do the work of moving you around. The burning of the gasoline and
expansion of gases it produces move the pistons in the engine, eventually moving you. Your body
uses chemical energy when it breaks down food, releasing the energy you need to do your work.
Summarize the paragraph above:
During physical and chemical reactions energy is either taken in or given off. One example you may
have seen is when ammonium nitrate in an ice pack reacts with water. This reaction takes in energy
from the surrounding area causing the temperature to decrease. Some changes give off energy.
This energy can be seen in several forms; the most common are heat, light, and sound. Dynamite
exploding gives off all three of these forms of energy.
Summarize the paragraph above:
The motion of the molecules in a substance is related to its temperature. As temperature increases,
the movement of the molecules also increases. This is due to the molecules gaining more energy;
therefore they move faster and spread out if there is room. This also works in reverse; the colder a
substance gets, the slower its particles move because they have lost their energy. This can be seen
as water boils and then freezes. When it is boiling, the molecules have lots of energy and are moving
all around. When it freezes the molecules slow down until they lock into a solid form.
Summarize the paragraph above:
Heat energy, also known as thermal energy, is related to temperature. Temperature can be
measured by the speed of the moving molecules as they hit a thermometer. Heat takes into
account how many molecules are moving at that speed. A large beaker of water and a small
beaker of water may be at the same temperature, but the large beaker has more heat.
Summarize the paragraph above:
When water is a solid, it has the least amount of energy. The molecules are hardly moving at all. As
energy is added to the ice, the molecules start moving faster until the ice begins to melt. When even
more energy is added, it will change from a liquid to a gas. The graph later in the study guide shows
how the temperature of water changes as heat is added. Notice the phase changes: there is no
increase or decrease in temperature!
Summarize the paragraph above:
Check Yourself!
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ENERGY AND MOLECULES
1. What happens to the motion of molecules in a substance when energy is added?
a. Taken away?
ENERGY AND CHEMICAL CHANGES
2. Give five examples of energy being released during a chemical change.
3. Explain how temperature is related to the energy in a chemical change.
4. Give two examples of exothermic reactions.
5. Give two examples of endothermic reactions.
6. What is the “rate” of a reaction?
a. What are some things we can do to increase the rate of reaction?
b. What are some things we can do to decrease the rate of reaction?
7. How does adding energy to a chemical change affect the reaction?
8. How does removing energy from a chemical change affect the reaction?
9. In the table to the right draw a picture of the molecules
before and during an exothermic reaction, and the
molecules before and during an endothermic reaction.
ENERGY AND PHASE CHANGES
10. Why doesn’t temperature increase when a substance is changing phase, even if you are still adding
energy?
11. Which has more kinetic energy, water in a gas phase, or water in a liquid phase?
12. When ice melts, is it losing or gaining energy?
13. Label each diagram below as a cold solid, hot solid, cold liquid, hot liquid, cold gas, or hot gas.
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Listed below are different pieces of information that can be identified on a phase change graph of water. For
each piece of information find the correct place on the graph and write the corresponding letter(s) next to
each item. Note: many of them will have more than one answer.
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
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12)
13)
14)
15)
16)
17)
Boiling point __________
Melting point __________
Phase change __________
Melting __________
Freezing __________
Condensing __________
Evaporating/boiling __________
Solid warming up __________
Solid cooling down __________
Liquid warming up __________
Liquid cooling down __________
Molecules using energy to change phase _______
Gas heating up __________
Gas cooling down __________
Molecules moving slowly __________
Molecules moving very quickly __________
Molecules are tightly packed __________
18)
19)
20)
21)
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23)
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27)
28)
Molecules are loosely packed __________
Molecules are widely spaced __________
Molecules have high kinetic energy __________
Molecules have low kinetic energy __________
Temperature is increasing __________
Temperature is decreasing __________
Temperature is staying constant __________
Energy is being added __________
Energy is being decreased __________
The temperature at which ice melts __________
The temperature at which liquid water evaporates or
boils __________
29) The temperature at which water vapor condenses
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30) The temperature at which liquid water freezes
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TYPES OF ENERGY AND ENERGY TRANSFORMATIONS
14. List all the different types of energy.
15. Listed below are objects that convert one type of energy to another. For each object, tell the original
type of energy it possesses, and then tell what kind of energy it transforms into. The first one is done for
you as an example.
ORIGINAL ENERGY TYPE
NEW ENERGY TYPE
(What the object produces)
Glow stick
Hand warmer
Flashlight (with battery)
Wind-up Flashlight
Electric Fan
Space Heater
Radio
Windmill
Microwave
Firecracker
Bicycle
Battery
16. Give an example where the following energy transformations might take place:
Electrical to thermal
Chemical to thermal
Electrical to mechanical (kinetic)