Download Mechanical Energy = Potential Energy + Kinetic Energy

Name__________________________________J# _______
Energy Transfer (Conversion)
KEY QUESTION
Energy Transfer (or Conversion): Can one form of energy be converted into another? By applying mechanical
energy to sand, can you change the temperature of sand (thermal energy)?
RESEARCH/BACKGROUND
The ability to do work is called energy. Work, therefore, occurs when energy is changed from one form to
another. There are many forms of energy. So far, you have learned about one of these forms of energy called
Mechanical energy--the energy associated with the motion (kinetic) or position (potential) of an object. For
example, when Ben Roethlisberger, my favorite Pittsburgh Steelers player, throws a football, the football has
mechanical energy. Before it leaves his hands it has stored energy (potential), and once he throws the ball it has
kinetic energy.
It is important to understand that all other types of energy involve potential and kinetic energy also. Most of the
other forms of energy are associated with the particles that make up objects. These particles are far too small
for you to see. Other forms of energy are chemical, thermal, electrical, electromagnetic, and nuclear:
Chemical energy is stored in the bonds of molecules (atoms), such as in the foods we eat.
Thermal energy is the total energy of the particles of an object (heat), such as melting ice cream due to the hot
air.
Electrical energy is the energy of electrical charges, such as the energy from batteries, electrical lines, or
lightning.
Electromagnetic energy travels in waves. These waves have some electrical properties and some magnetic
properties, such as sunlight, microwaves, x-rays, radio waves, infrared radiation.
Nuclear energy is energy stored (potential) in the nucleus of an atom. It is released with either the atoms split
(nuclear fission—used in nuclear power plants) or the atoms come together or fuse (nuclear fusion—what
occurs in the sun releasing tremendous amounts of energy).
Any form of energy can be changed into any other form. This change is known as an energy conversion. The
Law of Conservation of Energy states that energy cannot be created or destroyed. The total amount of energy,
therefore, is the same before and after an energy conversion; however, the amount of useful energy decreases
(there is some wasted or exerted on outside factors).
HYPOTHESIS
Make a statement that answers the second key question above. Give reasons for your hypothesis.
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MATERIALS
 16 oz plastic bottle with lid
 fine dry sand (approx. 500 mL)
 plastic or paper funnel
 tray or tub to collect sand spills
 Celsius thermometer
 goggles
PROCEDURE
1. Using the funnel, fill the plastic bottle ½ full with sand. Do this over a tray or tub to minimize the amount
of spillage.
2. Carefully place the bulb of the thermometer in the sand.
3. Wait two minutes; then measure the temperature of the sand and record it in the data table.
4. Cap the bottle tightly and shake it vigorously for exactly five minutes. If you get tired, pass it around to
your lab partners to take turns.
5. Repeat steps 2 and 3.
6. Get new sand in the bottle and repeat steps #1-5 for two more trials.
7. **While you are shaking, complete the additional data table (attached)—Celsius/Fahrenheit conversions.
SAFETY CONCERNS
Wear goggles. Clean up any spills; sand can make the floor very slippery. If sand gets in your eyes, inform
me!!! Use caution to avoid injuries.
OBSERVATIONS/DATA
Temperature
(degrees C)
Trial 1
oC
Trial 2
oC
Trial 3
oC
Average
oC
Uncertainty
oC
Start
20
21
20
20.3
.5
24
24.5
25
24.5
.5
After five
minutes of
shaking
True Value Range oC
19.8-20.8
24-25
GATHER AND ANALYZE DATA /GRAPH
Make a bar graph of the average temperature (y-axis) and the time (x-axis) on the graph paper attached.
Yes…Bar Graph because they are amounts per time, not a change over time. Three separate trials.
CONCLUSIONS
My
hypothesis, if the amount of mechanical energy given to a
bottle of sand increased, then the thermal energy inside the
bottle would increase b/c the mechanical energy would
convert into thermal energy (more shaking = hotter sand)
was supported because the starting temperature of the sand
averaged 20.3 degrees Celsius and the ending temperatures
(after 5 minutes of shaking) ALL averaged higher (24.5
degrees) than my starting temperature (Trial 1, the temp rose
1. Write a Conclusion. Was your hypothesis correct? Cite reasons why or why not.
4 degrees, Trial 2 rose 3.5 degrees, and Trial 3 rose 5
degrees).
2. What is another way to test your hypothesis?
Varying answers
3. What did you hold constant to make sure your test was a valid one?
SHOULD HAVE held constant the amount of sand, amount
of shaking time, placement of thermometer, person shaking,
shaking speed. However, this was not necessarily the case.
Your experiment had some validity issues, but your data was
consistent enough to say that those constants had some
flexibility.
EVALUATION/ANALYSIS
1. Would changing the amount of sand used change the results? Why or why not?
Varying Thoughts
2. Would changing the size of the container used change the results? Why or why not?
Varying Thoughts
3. What kind of energy was contained in the sand after shaking? Explain. Don’t just write one word.
Thermal—Thermal energy is heat energy. The bottles were
hotter after they were shaken.
4. This experiment showed a transfer of energy. Show with a flow chart the transfer of energy from one type
to another that occurred here. Place the event that took place in the boxes and the energy type on the lines
below.
Food
Chemical
Arm Moving
Back and
Forth
Mechanical
Sand moving
Sand warms
(Friction)
Mechanical
Thermal
5. Did all of the first type of energy you applied to the sand transfer to the second type of energy you
measured? Meaning….was any energy wasted? Why or why not? Explain.
YES ---some was lost to the bottle (Thermal (warm bottle)
and Mechanical (vibrations)), to the air (Mechanical-Sound
and Thermal to air)
Average Temperature of 3 Trials (Celsius)
**Be sure you include a title, x-axis, y-axis, legend (if needed), and all units of measure.
How shaking a bottle of sand for 5
minutes affects the average
temperature (amount of kinetic thermal
energy) in the sand.
30
25
20
15
10
5
0
24.5
20.3
Start Time (0 Minutes)
After 5 minutes
Time (Minutes)