Track Energy Changes - Middle School Physical Science

1. What is the law used in energy tracking that states total energy is conserved in a closed system?

   Law of conservation of energy. Energy cannot be created or destroyed, only transformed.

2. What is an energy representation used to track energy before and after an interaction?

   A model showing energy forms and transfers in a system. Diagrams or charts help visualize energy changes in interactions.

3. Which energy form is associated with height in a gravitational field?

   Gravitational potential energy, $E_g$. Stored energy due to position above a reference point.

4. Find $E_g$ change: A $2\,\text{kg}$ object drops $3\,\text{m}$ with $g=10\,\text{m/s}^2$; what is $\Delta E_g$?

   $\Delta E_g = -60\,\text{J}$. Use $\Delta E_g = mg\Delta h = 2 \times 10 \times (-3)$.

5. What does an energy bar chart represent about a system at a specific moment (before or after)?

   The amounts of energy in each form for the chosen system at that time. Shows distribution of energy types at one instant.

6. Find the missing value in a closed system: before $E_k = 6\text{ J}$ and $E_g = 4\text{ J}$; after $E_g = 1\text{ J}$, so $E_k =$ ?

   $9\text{ J}$. Total energy $10\text{ J}$ conserved: $1 + E_k = 10$.

7. Which rule must be true for total energy in a correct energy bar chart?

   Total energy before equals total energy after (including transfers). Conservation of energy requires balanced totals.

8. What does an energy transfer representation (arrow) show in a diagram?

   Energy crossing the system boundary into or out of the system. Arrows indicate direction and amount of energy flow.

9. What rule states the total energy of a closed system stays the same during interactions?

   Law of conservation of energy. Energy cannot be created or destroyed, only transformed.

10. Which energy change best matches a stretched rubber band released: elastic potential decreases, kinetic increases?

    Elastic potential energy transforms to kinetic energy. Stored spring energy converts to motion when released.

11. Identify the missing energy: before $E_g=50\,\text{J}$, after $E_k=20\,\text{J}$, closed system; what is $E_{\text{th, after}}$?

    $30\,\text{J}$. Total before ($50\text{ J}$) equals total after ($20+E_{th}$).

12. Which statement correctly completes an energy bar chart for a closed system?

    Total energy before equals total energy after. Conservation of energy requires equal totals before and after.

13. Identify the energy change when a moving cart stops due to friction with the track.

    Kinetic energy decreases; thermal energy increases. Friction converts motion to heat in the system.

14. Which transfer pathway describes energy carried by light, microwaves, or other electromagnetic waves?

    Radiation. Electromagnetic waves carry energy through space without matter.

15. Find the correct system type: total energy before is $60\,\text{J}$ and after is $45\,\text{J}$ in the chart; what is it?

    Open system (energy left the system). $15\text{ J}$ disappeared, violating closed system rules.

16. Identify the correct gravitational potential energy formula near Earth's surface.

    $GPE = mgh$. Energy equals mass times gravity times height.

17. What is the correct sign meaning for work done on a system in energy accounting?

    Positive work adds energy to the system; negative work removes energy. Work transfers energy into (+) or out of (-) the system.

18. What is the purpose of an energy representation when analyzing an interaction?

    To track energy storage and transfers before and after the interaction. Energy representations show where energy is stored and how it moves during interactions.

19. What is the energy storage associated with temperature and particle motion called in models?

    Thermal energy. Energy from random motion of particles within matter.

20. What is the energy form associated with moving electric charges called?

    Electrical energy. Energy carried by flowing electrons in circuits.

21. Identify the meaning of an energy transfer arrow crossing the system boundary.

    Energy enters or leaves the system to or from the surroundings. Arrows show energy crossing the system boundary.

22. Identify the correct statement about total energy in a closed system during an interaction.

    Total energy stays constant; only the distribution among forms changes. Energy conservation: can't create or destroy energy.

23. What is $GPE$ if $m = 2\ \text{kg}$, $g = 10\ \text{N/kg}$, and $h = 3\ \text{m}$?

    $GPE = 60\ \text{J}$. Multiply: $2 \times 10 \times 3 = 60$ J.

24. Identify the energy change: a ball falls and speeds up; which transformation best matches a closed system model?

    Gravitational potential energy decreases; kinetic energy increases. Height energy converts to speed energy as objects fall.

25. Identify the correct equation for an open system: $E_{\text{before}} + E_{\text{in}}$ ___ $E_{\text{after}} + E_{\text{out}}$.

    $E_{\text{before}} + E_{\text{in}} = E_{\text{after}} + E_{\text{out}}$. Accounts for energy flowing in and out of open systems.

26. Which statement best describes an open system in energy tracking?

    Energy can cross the system boundary. External energy can be added or removed from the system.

27. Which statement best describes "dissipated energy" in middle school energy models?

    Energy spread into thermal energy, harder to use for doing work. Thermal energy is less organized and useful.

28. Identify the missing energy: before $E_k=40\,\text{J}$, after $E_k=10\,\text{J}$, closed system; what is the increase in $E_{\text{th}}$?

    $30\,\text{J}$. Lost kinetic energy ($40-10$) becomes thermal energy.

29. Which energy type is stored due to an object's height in a gravitational field?

    Gravitational potential energy. Higher objects store more energy due to gravity's pull.

30. What rule must be satisfied when comparing total energy before and after an interaction?

    Total energy is conserved: $E_{before} = E_{after}$. Energy cannot be created or destroyed, only transformed or transferred.

31. What is the formula for kinetic energy for a mass $m$ moving at speed $v$?

    $KE = \frac{1}{2}mv^2$. Mass times velocity squared, divided by two.

32. Identify the correct statement for an open system energy chart when energy enters the system from outside.

    Total after energy can be greater than total before energy. External energy input increases system's total energy.

33. What is the correct expression for kinetic energy of a moving object?

    $E_k = \frac{1}{2}mv^2$. Half the mass times velocity squared.

34. Which energy change best matches a flashlight: chemical energy in battery decreases, radiant increases?

    Chemical energy transforms to radiant energy (and some thermal). Battery's stored energy converts to light (and waste heat).

35. Which energy form increases when an object is lifted higher in a gravitational field?

    Gravitational potential energy. Height in a gravity field stores potential energy.

36. Which energy form is associated with separated electric charges in a system?

    Electric potential energy, $E_{el}$. Energy stored when opposite charges are separated by distance.

37. What is the energy form associated with vibrations traveling through matter called?

    Sound energy. Energy carried by pressure waves through materials.

38. Choose the correct energy bar-chart conclusion: if $E_{before} < E_{after}$, what must be true?

    Net energy was transferred into the system ($E_{in} > E_{out}$). System gained energy; more energy entered than left.

39. Find the energy transferred out as heat: total before $12\text{ J}$, total after $7\text{ J}$, no other transfers; $E_{\text{out}} =$ ?

    $5\text{ J}$. Energy difference shows heat lost to surroundings.

40. What is the meaning of the term system in an energy tracking problem?

    The objects being analyzed for energy changes. Defines the boundary for tracking energy changes.

41. Which energy form is associated with motion of an object?

    Kinetic energy. Moving objects have kinetic energy proportional to speed squared.

42. Which energy form is associated with an object's motion?

    Kinetic energy. Moving objects have kinetic energy proportional to mass and speed squared.

43. What does the law of conservation of energy state for a closed system?

    Total energy stays constant; it only changes form or location. Energy cannot be created or destroyed in isolated systems.

44. Which energy type is stored in chemical bonds (food, fuel, batteries)?

    Chemical energy. Energy stored in molecular bonds, released in reactions.

45. Which two transfer pathways are typically shown crossing a system boundary in middle school models?

    Work and heat. The two main ways energy moves between system and surroundings.

46. Which energy type is associated with moving electric charges in a circuit?

    Electrical energy. Flowing electrons carry energy through conductors.

47. What is the first step when using an energy representation for an interaction?

    Define the system and the surroundings. Establishes boundaries to track where energy flows.

48. What is the law used in energy tracking that states total energy is conserved?

    Law of Conservation of Energy. States that energy cannot be created or destroyed, only transformed.

49. What is elastic potential energy in words for energy representations?

    Stored energy in stretched or compressed materials. Springs and rubber bands store this when deformed.

50. Which equation correctly represents conservation for a closed system with only $E_g$ and $E_k$ changing?

    $E_{g,i}+E_{k,i}=E_{g,f}+E_{k,f}$. Total energy before equals total energy after.

51. What is the key difference between energy transfer and energy transformation?

    Transfer crosses a boundary; transformation changes form within a system. Transfer moves energy between systems; transformation converts between forms.

52. What is the correct expression for elastic potential energy stored in a stretched spring?

    $E_{\text{el}} = \frac{1}{2}kx^2$. Half the spring constant times displacement squared.

53. Which energy form is carried by waves such as light or sound?

    Radiant energy (light) or sound energy (waves). Electromagnetic and mechanical waves transport energy.

54. Which energy storage form often increases when friction causes warming during motion?

    Thermal energy. Random molecular motion energy that manifests as temperature.

55. What is the definition of a system when using energy representations?

    The objects chosen for analysis; everything else is the surroundings. Defines the boundary between what we're studying and everything else.

56. A closed system has $E_{\text{total}} = 120\ \text{J}$. After, $KE = 70\ \text{J}$. What is the remaining energy?

    $50\ \text{J}$. Total energy conserved: $120 - 70 = 50$ J in other forms.

57. What does chemical energy represent in an energy bar chart?

    Stored energy in chemical bonds (food, fuel, batteries). Breaking bonds releases this stored energy.

58. Identify the energy change: A moving cart slows due to friction; where does energy go?

    $E_k$ decreases and $E_{th}$ increases. Friction converts motion energy to heat energy.

59. Find the correct conclusion: If $E_i = 20\text{ J}$, $E_{in} = 10\text{ J}$, and $E_{out} = 5\text{ J}$, what is $E_f$?

    $25\text{ J}$. Apply conservation: $20 + 10 = E_f + 5$, so $E_f = 25\text{ J}$.

60. What must be true about total energy bars before and after for a closed system?

    Total before equals total after. Conservation of energy requires equal totals.

61. What is the energy storage associated with motion called?

    Kinetic energy. Energy due to an object's speed and mass.

62. What does a negative energy transfer into the system indicate on an energy diagram?

    Energy leaves the system to the surroundings. System loses energy when transfer is negative.

63. Which energy form is stored in a stretched or compressed spring or elastic object?

    Elastic potential energy. Deformed elastic materials store energy that releases when returning to shape.

64. Which energy form is associated with motion in energy bar charts?

    Kinetic energy, $E_k$. Energy of moving objects, depends on mass and speed.

65. What is the definition of a system in an energy analysis?

    The object(s) chosen for study, separated from surroundings. Everything outside the system is the surroundings.

66. What is an energy representation used for when comparing before and after an interaction?

    A model that tracks energy forms and transfers during a change. Shows how energy changes form and location during interactions.

67. Which energy change best matches a sliding object that slows due to friction on a table?

    Kinetic decreases while thermal energy of objects increases. Friction converts kinetic energy to heat.

68. What does a larger bar in an energy bar chart represent?

    A greater amount of energy in that form. Bar height is proportional to energy quantity.

69. Which energy form typically increases when two surfaces rub and warm up?

    Thermal energy. Friction converts kinetic energy to heat.

70. Which energy forms increase in a hand-rubbing interaction, and which decreases?

    Thermal increases; kinetic of hands decreases. Friction converts hand motion to heat energy.

71. Which equation summarizes energy tracking with transfers: $E_i + E_{in} = E_f + E_{out}$?

    $E_i + E_{in} = E_f + E_{out}$. Conservation equation balancing initial, final, and transferred energies.

72. What does the term system mean in an energy tracking problem?

    The objects being analyzed for energy changes. The specific objects whose energy changes we're tracking.

73. What is the key first step when making an energy representation for an interaction?

    Define the system and identify what is in the surroundings. Clear boundaries determine what energy to track.

74. What is thermal energy in energy tracking representations?

    Energy associated with random motion of particles (heating). Temperature indicates this microscopic kinetic energy.

75. What does the thermal energy bar in an energy representation usually indicate about an interaction?

    Energy spread out as heating due to friction, collision, or contact. Friction converts mechanical energy to heat.

76. Identify the missing energy form: battery powers a motor that spins a fan; chemical becomes what?

    Chemical energy becomes kinetic energy (with some thermal energy). Motors convert electrical energy from batteries to motion.

77. Which energy storage form increases when a spring or rubber band is stretched or compressed?

    Elastic potential energy. Energy stored in deformed elastic materials.

78. What is the energy form associated with light (electromagnetic waves) called?

    Radiant energy. Energy carried by electromagnetic waves like visible light.

79. Which energy form increases in a resistor or filament when electric current runs through it?

    Thermal energy. Electrical resistance converts electrical energy to heat.

80. Find the missing energy after: before $E_g=40\,J$, after $E_k=25\,J$ and $E_{th}=15\,J$.

    Missing energy is $0\,J$ (total after is $40\,J$). Total energy conserved: $40=25+15+0$.

81. Which energy form increases when a moving object slows due to friction in a closed system?

    Thermal energy increases. Friction converts kinetic to thermal energy.

82. What rule must be satisfied in every energy representation for a closed system?

    Total energy stays constant (energy is conserved). Energy cannot be created or destroyed in isolated systems.

83. Which energy change is most consistent with a falling object with negligible air resistance?

    Gravitational potential decreases while kinetic increases. GPE converts to KE as object accelerates downward.

84. Find the speed from energy: If $m=4\,\text{kg}$ and $E_k=50\,\text{J}$, what is $v$?

    $v = 5\,\text{m/s}$. Solve $50 = \frac{1}{2}(4)v^2$ gives $v^2 = 25$.

85. What is the energy conservation rule to apply when tracking energy before and after an interaction?

    Total energy before = total energy after. Energy cannot be created or destroyed, only transferred or transformed.

86. What is the correct conservation equation using system energy and transferred energy?

    $E_{\text{before}} + E_{\text{in}} = E_{\text{after}} + E_{\text{out}}$. This equation balances all energy in the system.

87. What is the term for energy transfer due to a temperature difference (hot to cold)?

    Heat. Thermal energy flows from warmer to cooler objects.

88. What is the correct expression for gravitational potential energy near Earth's surface?

    $E_g = mgh$. Height $h$ times mass $m$ times gravity $g$.

89. Which energy form increases when the temperature of matter increases?

    Thermal energy. Related to particle motion; higher temp means more thermal energy.

90. Choose the correct conclusion: In a closed system, energy bars sum to $80\,\text{J}$ before. What must they sum to after?

    $80\,\text{J}$. Energy conservation requires constant total.

91. What is the final kinetic energy if $m=2\,\text{kg}$ and $v=3\,\text{m/s}$?

    $9\,\text{J}$. Using $KE=\frac{1}{2}mv^2=\frac{1}{2}(2)(3^2)=9\,\text{J}$.

92. Which energy form is associated with the temperature of matter and particle motion inside it?

    Thermal energy. Random particle motion increases with temperature, storing thermal energy.

93. Which choice best describes an open system in energy tracking?

    Energy can cross the system boundary to or from the surroundings. Energy exchange with surroundings is possible.

94. Identify the energy change: A stretched spring launches a cart on a smooth track.

    Elastic potential decreases; KE increases. Stored spring energy converts to motion energy.

95. Which energy transfer mechanism is shown when a battery powers a bulb through a circuit?

    Electrical energy transfer from battery to bulb. Current carries energy from source to load.

96. What is the definition of a system in an energy representation?

    The object(s) chosen for analysis and their stored energies. Defines the boundary for tracking energy storage and transformations.

97. Which energy form is stored in fuels, food, and batteries?

    Chemical energy, $E_{ch}$. Energy stored in molecular bonds, released in reactions.

98. Which energy transformation best matches a stretched rubber band that is released?

    Elastic potential energy transforms into kinetic energy. Stored elastic energy converts to motion when released.

99. Which transfer pathway describes energy carried by moving electric charges in a circuit?

    Electrical transfer. Electric current carries energy through conducting materials.

100. Identify the missing term: Energy crossing the system boundary by a force doing work is called ______.

     Work. Forces acting through distances transfer energy as work.

101. Which term names energy that changes form within the same system during an interaction?

     Energy transformation. Energy converts between forms (e.g., kinetic to potential) within one object.

102. A ball's $GPE$ decreases by $40\ \text{J}$. If no energy leaves the system, how much does $KE$ increase?

     $40\ \text{J}$. In closed systems, lost GPE equals gained KE.

103. Which choice best describes a closed system in energy tracking?

     No energy enters or leaves the system; only energy changes form inside. Energy is isolated within the boundary and can only transform.

104. What is the energy form stored in a stretched or compressed object called?

     Elastic potential energy. Springs and rubber bands store energy when deformed.

105. Which energy type is associated with temperature and particle motion inside matter?

     Thermal energy. Random molecular motion creates heat energy.

106. Which energy form is stored when a spring or rubber band is stretched or compressed?

     Elastic potential energy. Deformed elastic materials store energy that can be released.

107. Which energy representation is correct for a flashlight: battery energy decreases, light and heat increase?

     Chemical energy decreases; radiant and thermal energy increase. Battery's chemical energy converts to light and heat.

108. What is the difference between energy transferred and energy transformed in an interaction?

     Transferred: crosses system boundary; transformed: changes form within system. Transfer moves energy between systems; transformation changes its type.

109. Identify the energy change: A sliding box slows down on a rough floor (no height change).

     KE decreases; thermal energy increases. Friction converts motion energy to heat.

110. Which energy form typically increases when friction acts during motion on a surface?

     Thermal energy increases. Friction converts kinetic energy to heat.

111. What is the best definition of a system in energy tracking problems?

     The objects you choose to analyze for energy changes. Define your system boundary to track energy flow in and out.

112. Identify the energy transformation in a flashlight converting battery energy to light.

     Chemical energy transforms to electrical then radiant (and thermal). Battery's stored chemical energy powers the circuit.

113. What is the definition of the surroundings in an energy representation?

     Everything outside the system that can exchange energy with it. Includes all matter and energy not included in the system.

114. Identify the correct equation for energy tracking with transfers: stored energy change equals what?

     $ Delta $E_{stored}$ = $E_{in}$ - $E_{out}$$. Change in stored energy equals energy flowing in minus energy flowing out.

115. Identify the correct energy change when a moving cart hits a spring and stops briefly: $E_k$ and $E_e$.

     $E_k$ decreases to $0$; $E_e$ increases. Cart's motion energy transfers to spring compression.

116. What must be true on an energy bar chart for a closed system (no energy enters or leaves)?

     Total before energy equals total after energy. Conservation requires equal total energy before and after.

117. What does an energy bar chart represent in a before-and-after interaction model?

     Relative amounts of energy in each form before and after an interaction. Shows how energy quantities change between initial and final states.

118. What does an energy storage representation (bar chart or pie chart) show?

     Energy amounts in each form at one moment (before or after). Snapshots show how energy is distributed among different forms.

119. Which energy form is stored due to an object's position in a gravitational field?

     Gravitational potential energy. Objects higher up store energy that can convert to kinetic when falling.

120. What does elastic potential energy represent in an energy bar chart?

     Stored energy due to stretching or compressing an elastic object. Springs and rubber bands store this when deformed.

121. What is the energy storage associated with height in a gravitational field called?

     Gravitational potential energy. Energy stored due to position above a reference point.

122. Which energy change best matches braking a bike: kinetic energy decreases and thermal energy increases?

     Kinetic energy transforms to thermal energy (friction). Motion energy converts to heat via brake friction.

123. What is the definition of an energy transfer in an energy representation?

     Energy moving from one object or system to another. Energy crosses system boundaries between separate objects.

124. Which energy transfer label describes energy moved by a force over a distance?

     Work. Mechanical energy transfer through applied forces.

125. What is the key difference between energy transfer and energy transformation?

     Transfer: energy moves systems; transformation: energy changes form. Transfer crosses boundaries; transformation stays in same place.

126. Which energy form decreases in a battery when it powers a device?

     Chemical energy. Batteries convert stored chemical energy to electrical energy.

127. What does a system boundary represent in an energy diagram or energy bar chart?

     What is included in the system being analyzed. Defines what's inside vs. outside for energy accounting.

128. Choose the correct relationship for kinetic energy when speed doubles: $v \rightarrow 2v$ implies $E_k \rightarrow$ what?

     $E_k$ becomes $4E_k$. Kinetic energy depends on speed squared: $E_k = \frac{1}{2}mv^2$.

129. Which energy storage is associated with energy stored in chemical bonds (food, fuel, batteries)?

     Chemical energy. Energy stored in molecular bonds that releases during chemical reactions.

130. What is the definition of an energy transformation in an energy representation?

     Energy changing from one form to another within a system. Energy converts between forms while staying in the same system.

131. Identify the energy change in a falling object (ignore air resistance): $E_g$ decreases, what increases?

     Kinetic energy increases. Gravitational potential converts to motion energy.

132. Identify the energy change: A falling object speeds up while losing height (ignore air resistance).

     GPE decreases; KE increases by the same amount. Gravity converts height energy to motion energy.

133. Which energy storage form depends on height in a gravitational field near Earth?

     Gravitational potential energy. Stored energy due to position above a reference point.

134. What is gravitational potential energy in words for energy representations?

     Stored energy due to height in a gravitational field. Higher objects have more of this energy.

135. Identify the correct energy change: A ball compresses a spring and stops; $E_k$ decreases and what increases?

     Elastic potential energy increases. Kinetic energy transforms to spring's stored energy.

136. Identify the correct energy bar change for a dropped ball ignoring air resistance: $E_g$ and $E_k$.

     $E_g$ decreases; $E_k$ increases; total stays constant. Gravitational converts to kinetic as the ball falls.

137. Which transfer pathway describes energy moving because of a temperature difference?

     Heating (thermal transfer). Heat flows from hot to cold objects due to temperature differences.

138. Which energy transfer pathway is described by a force acting through a distance?

     Work. Force times distance transfers energy mechanically.

139. Find the missing amount: before total is $12\ \text{J}$, after internal energy is $9\ \text{J}$; what transfer out occurred?

     $3\ \text{J}$ transferred out of the system. Conservation: $12\ \text{J} - 9\ \text{J} = 3\ \text{J}$ lost.

140. What energy representation shows energy storage and transfers using boxes and arrows?

     Energy bar chart (bar model). Visual tool using bars to show energy amounts and arrows for transfers.

141. Which energy form increases when objects warm up due to friction or heating?

     Thermal energy, $E_{th}$. Random kinetic energy of particles at molecular level.

142. Find the final kinetic energy if $E_g$ decreases by $30\,\text{J}$ and thermal increases by $10\,\text{J}$ in the same system.

     $E_k$ increases by $20\,\text{J}$. Conservation: lost $E_g$ minus thermal gain equals $E_k$ gain.

143. What does a transfer arrow across the system boundary represent in an energy diagram?

     Energy entering or leaving the system. Shows energy crossing between system and surroundings.

144. What is the correct system statement if you choose the system as "ball + Earth" for a falling ball?

     Gravitational energy is internal to the system (not transferred in). When Earth is in the system, gravity is an internal interaction, not external transfer.

145. Identify the energy transfer: A battery powers a motor in the system; is energy in or out?

     Energy transfers into the motor system from the battery ($E_{in}>0$). Battery supplies energy to motor, crossing system boundary inward.

146. Which energy storage increases when the temperature of matter increases?

     Thermal energy. Heat is a form of energy related to particle motion and temperature.

147. What term describes energy moving from one object or system to another during an interaction?

     Energy transfer. Energy moves between objects or systems during interactions.

148. What is the energy form of motion of an object called?

     Kinetic energy. Energy of moving objects, depends on mass and speed.

149. What does a positive energy transfer into the system indicate on an energy diagram?

     Energy enters the system from the surroundings. System gains energy when transfer is positive.

150. Identify the missing term: If no energy crosses the boundary, then $E_i$ equals what?

     $E_f$. With no transfers, initial energy equals final energy.

151. Which energy form decreases as an object falls (ignoring air resistance) while speed increases?

     Gravitational potential energy decreases. Height decreases, so $mgh$ decreases.

152. Which energy form is associated with an object's position in a gravitational field?

     Gravitational potential energy. Higher objects have more GPE relative to a reference point.

153. Which option best represents a falling object with no air resistance: $E_g$ decreases and which form increases?

     Kinetic energy increases. Gravitational potential converts to motion energy during free fall.

154. Which energy transfer is represented when a battery powers a motor in the system?

     Chemical energy decreases while electrical and then kinetic energy increase. Battery's stored energy converts to motion.

155. Which energy storage is associated with an object moving due to its speed?

     Kinetic energy. Moving objects have energy due to their motion.

156. Identify the energy change: A book is lifted at constant speed; which storage increases?

     Gravitational potential energy increases. Lifting increases height, storing more gravitational energy.

157. Which energy forms are most common in middle school energy bar charts?

     Kinetic, gravitational potential, elastic potential, thermal, chemical. These five forms cover most middle school scenarios.

158. Identify the missing energy: before $E_e=25\,\text{J}$, after $E_k=15\,\text{J}$, closed system; what is $E_{\text{th, after}}$?

     $10\,\text{J}$. Elastic energy ($25\text{ J}$) converts to kinetic ($15$) and thermal.

159. What is the term for energy transferred by a force acting through a distance?

     Work. Force × distance transfers energy between objects.

160. What is the missing energy form: A sliding box slows down and the surface warms; $E_k$ decreases and ______ increases.

     Thermal energy increases. Friction converts motion to heat.

161. Which energy storage is associated with an object's height in a gravitational field?

     Gravitational potential energy. Objects higher up store energy that can be released when falling.

162. What does it mean if energy is dissipated during an interaction?

     Energy spreads out, often as thermal, and is less useful for work. Energy becomes harder to harness for useful purposes.

163. Identify the energy change: A spring launches a toy car; which energy transforms?

     $E_e$ decreases and $E_k$ increases. Stored spring energy converts to motion energy when released.

164. What is kinetic energy in words for middle school energy bar charts?

     Energy of motion. Objects in motion have this type of energy.

165. Which statement best describes an isolated (closed) system in energy tracking?

     No energy enters or leaves the system boundary. Total energy stays constant with no external exchanges.

166. What is the law used when tracking energy before and after an interaction in a system?

     Energy is conserved: total energy change is $0$ in a closed system. Energy cannot be created or destroyed, only transformed.

167. Find the missing energy type: A cup of hot water cools; thermal energy decreases and energy leaves as ____.

     Thermal energy transferred to surroundings as heat. Temperature difference drives thermal energy flow outward.

168. Identify the transfer: A person pushes a box across the floor; energy crosses the boundary as what?

     Work. Force applied through distance transfers energy as work.

169. What is the law used when tracking energy before and after an interaction?

     Energy is conserved; it changes form or transfers, not created or destroyed. This fundamental principle governs all energy interactions.

170. What is the law that states total energy in a closed system stays constant during interactions?

     Law of Conservation of Energy. Energy cannot be created or destroyed, only transformed or transferred.

171. What does thermal energy represent in an energy bar chart?

     Energy related to temperature and particle motion within matter. Faster particle motion means higher temperature.

172. Which option best describes an open system in energy tracking?

     A system that can exchange energy with its surroundings. Closed systems cannot exchange energy with surroundings.

173. Which system choice is best for a block slowing down due to friction with the floor: block only or block+floor?

     Block+floor (includes thermal energy increase inside the system). Friction converts kinetic to thermal energy within the system.

174. Which energy type is carried by waves such as light and infrared?

     Radiant (electromagnetic) energy. Energy traveling as electromagnetic waves through space.

175. A closed system has $20\,\text{J}$ total energy before; after it has $5\,\text{J}$ kinetic. What must the other forms total?

     $15\,\text{J}$. Conservation: $20\,\text{J}$ total $-$ $5\,\text{J}$ kinetic $=$ $15\,\text{J}$ other.

176. Identify the energy change: An object speeds up without changing height; which storage increases?

     Kinetic energy increases. Speed increase means more energy of motion.

177. Identify the missing term: Energy crossing the system boundary by heating is called ______.

     Thermal transfer (heating). Heat flow transfers thermal energy across system boundaries.

178. Which energy transfer pathway involves waves such as light or infrared?

     Radiation. Electromagnetic waves carry energy without matter.

179. What does an energy representation (bar chart or diagram) show about a system?

     Energy amounts in each form and transfers into or out of the system. These visual tools help track conservation of energy.

180. What does gravitational potential energy represent in an energy bar chart?

     Stored energy due to position (height) in a gravitational field. Higher objects have more of this stored energy.

181. Which option best describes a closed system in energy tracking?

     No energy crosses the boundary; only energy transformations occur. System is isolated from surroundings, conserving total energy.

182. What is the formula for kinetic energy of a mass $m$ moving at speed $v$?

     $KE=rac{1}{2}mv^2$. Mass times velocity squared, divided by two.

183. Which transfer pathway describes energy moving by mechanical forces doing work (pushes, pulls, friction)?

     Work (mechanical transfer). Forces transfer energy when they cause displacement.

184. Which energy form is stored in chemical bonds (such as food, fuel, or batteries)?

     Chemical energy. Breaking bonds releases energy; forming bonds stores energy.

185. What energy form is stored in a stretched or compressed spring or rubber band?

     Elastic potential energy. Deformed elastic materials store recoverable energy.

186. Identify the correct equation for a closed system: $E_{\text{total,before}}$ ___ $E_{\text{total,after}}$.

     $E_{\text{total,before}} = E_{\text{total,after}}$. Conservation law: no energy enters or leaves a closed system.

187. What is the energy form stored due to position in a gravitational field called?

     Gravitational potential energy. Energy stored by height above a reference point.

188. Find the missing energy: $E_{before}=50\,J$, $E_{out}=12\,J$, so what is $E_{after}$?

     $38\,J$. Conservation: $E_{after} = E_{before} - E_{out} = 50 - 12 = 38\,J$.

189. Which term names energy that moves into or out of a system because of a force over a distance?

     Work. Force applied through a distance transfers energy.

190. What is the gravitational potential energy if $m=1\,\text{kg}$, $g=10\,\text{N/kg}$, $h=2\,\text{m}$?

     $20\,\text{J}$. Using $GPE=mgh=(1)(10)(2)=20\,\text{J}$.

191. Identify the energy change: A ball falls and speeds up; what decreases and increases?

     $E_g$ decreases and $E_k$ increases. Gravity converts height energy to motion energy during fall.

192. Find the missing after-energy: system has $E_{\text{before}}=20\ \text{J}$ and $E_{\text{out}}=5\ \text{J}$; what is $E_{\text{after}}$ if $E_{\text{in}}=0$?

     $15\ \text{J}$. Conservation: $20\ \text{J} - 5\ \text{J} = 15\ \text{J}$ remains.

193. Which energy form increases when an object speeds up (without height change)?

     Kinetic energy. Moving objects have kinetic energy proportional to $v^2$.

194. Which energy type is stored in a stretched or compressed spring or rubber band?

     Elastic potential energy. Deformed elastic materials store recoverable energy.

195. What is the formula for gravitational potential energy near Earth for height $h$?

     $GPE=mgh$. Mass times gravitational field strength times height.

196. What is the meaning of the term surroundings in an energy tracking problem?

     Everything outside the chosen system. Includes all matter and energy not in the system.

197. Which energy storage is associated with a stretched or compressed spring or elastic band?

     Elastic potential energy. Deformed elastic materials store energy that releases when returning to shape.

198. What is the law used when tracking energy before and after an interaction in a system?

     Energy is conserved; it changes form but total stays constant. This fundamental principle states energy cannot be created or destroyed.

199. Identify the correct kinetic energy formula used in energy representations.

     $KE = \frac{1}{2}mv^2$. Energy equals half mass times velocity squared.

200. What does kinetic energy represent in an energy bar chart?

     Energy of motion. Objects with velocity have this form of energy.

201. Find the missing after-energy: Before $E_k=6$ J, $E_g=4$ J; after $E_g=1$ J, closed system. What is after $E_k$?

     After $E_k=9$ J. Total energy conserved: $6+4=10$ J before equals $9+1=10$ J after.

202. Identify the correct equation for conservation of energy in a closed system.

     $E_{\text{total, before}}=E_{\text{total, after}}$. Mathematical statement of energy conservation.

203. What does the term surroundings mean in an energy tracking problem?

     Everything outside the system boundary. All matter and energy not included in the defined system.

204. Which option best represents a sliding box slowing from friction: kinetic energy decreases and which form increases?

     Thermal energy increases. Friction converts motion energy into heat.

205. Identify the missing form: a compressed spring is released and the cart speeds up; elastic energy decreases and ___ increases.

     Kinetic energy increases. Spring's stored energy converts to motion energy.

206. What is the energy storage associated with chemical bonds called?

     Chemical energy. Energy stored in molecular bonds that can be released.

207. Which energy change best matches a ball falling with little air resistance: $E_g$ decreases, $E_k$ increases?

     Gravitational potential energy transforms to kinetic energy. Height energy converts to motion energy as object falls.

208. Which option correctly describes the system boundary in energy diagrams?

     An imaginary surface separating the system from the surroundings. Defines what's inside vs. outside the system.

209. Identify the energy change when a moving cart slows down due to friction on a rough floor.

     Kinetic decreases; thermal energy of cart+floor increases. Friction converts motion energy into heat, warming both surfaces.

210. Which energy type is energy of motion that increases with speed?

     Kinetic energy. Objects in motion have this energy; faster = more energy.

211. What is the energy form stored in chemical bonds called?

     Chemical energy. Energy stored in molecular bonds, released in reactions.

212. Find the after kinetic energy: before $E_k=60\,J$, $20\,J$ transfers out as heating to surroundings.

     $E_k=40\,J$. Initial minus heat lost: $60-20=40\,J$.

213. What is the best definition of the surroundings in an energy tracking problem?

     Everything outside the chosen system. The surroundings interact with your system through energy exchange.

214. Which energy transfer pathway is described by temperature difference between objects?

     Heating (heat transfer). Hot objects transfer energy to cold ones.

215. Find $E_{out}$: $E_{before}=90\,J$, $E_{after}=65\,J$. How much energy left the system?

     $25\,J$. Energy left system: $E_{out} = E_{before} - E_{after} = 90 - 65 = 25\,J$.

216. Which energy transfer label describes energy moved because of a temperature difference?

     Heat. Thermal energy flows from hot to cold regions.

217. What is the energy storage associated with stretched or compressed objects called?

     Elastic potential energy. Energy stored in deformed elastic materials like springs.

218. Which storage increases when a compressed spring launches a toy car and the spring relaxes?

     Kinetic energy increases as elastic potential energy decreases. Spring releases stored elastic energy, converting it to car's motion.

219. Which energy storage form increases when an object speeds up?

     Kinetic energy. Energy of motion, proportional to mass and velocity squared.

220. Which energy form is stored in a stretched or compressed spring or rubber band?

     Elastic potential energy, $E_e$. Stored when elastic materials are deformed from equilibrium.

221. Identify the energy change for a dropped book that speeds up while falling (ignore air resistance).

     Gravitational potential decreases; kinetic increases; total stays constant. As the book falls, height energy converts to motion energy; total conserved.

222. What is the law used in energy bar charts that compares total energy before and after an interaction?

     Energy is conserved: $E_{\text{total,before}} = E_{\text{total,after}}$. Total energy remains constant in isolated systems.

223. Which option best describes an open system in energy tracking?

     Energy crosses the boundary to or from the surroundings. System exchanges energy with surroundings through transfers.

224. Which option correctly completes this statement: In a closed system, $\Delta E_{total} =$ what value?

     $0$. Total energy remains constant in isolated systems.

225. What energy representation lists initial, transfers, and final energy in a structured format?

     Energy flow diagram (system energy diagram). Organizes energy states and transfers in a systematic table format.

226. Identify the energy change when a battery powers a motor that lifts a mass at constant speed.

     Chemical energy decreases; gravitational potential energy increases. Battery's stored energy lifts mass against gravity.

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