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Energy Paths Around the Backyard Sandbox

Use a class investigation to trace energy from one place to another.

Start with the Buzzer

Read the class investigation. Use the observations to answer the questions.

A Backyard Science Visit

During a supervised science visit, Ms. Chen's class investigated energy around her backyard sandbox. They used a dry board beside the sandbox for equipment. Students recorded what changed at a place away from an energy source. They completed one test at a time so the equipment from one test would not affect another.

First, the class connected a low-voltage battery, wires, a switch, and a small buzzer. The battery was one meter from the buzzer. Imani listened from the other side of the sandbox. With the switch open, she heard no buzz. Closing the switch made the buzzer sound. Opening it stopped the sound. They repeated this three times without moving the battery, buzzer, or listener. The buzzer setting stayed the same.

Next, students stood a white card in shade inside the sandbox. A small mirror rested at a sunny edge. An adult adjusted the mirror until a bright patch appeared on the card one meter away. Turning the mirror face down removed the patch. Returning it to its earlier position brought the patch back. The card stayed in shade.

With the mirror aimed at the card, students placed cardboard across the path between them. The bright patch disappeared. They then moved the cardboard behind the card, away from that path. The bright patch returned. They kept the mirror and card in the same positions.

Finally, students put equal amounts of dry sand into three identical thin plastic trays. Each sample began at 26°C. An adult supplied two identical sealed cold packs kept near 8°C. One tray rested directly on a pack. Another rested on a foam sheet placed on the second pack. The third tray rested on the board without a pack.

All three trays stayed in shade for eight minutes. The air remained near 26°C. Students kept the sand depth, tray type, and measuring time the same. They measured the sand at the same depth in each tray. The packs stayed sealed, so no pack liquid entered the sand. The graph shows the final temperatures.

1.
The buzzer sounded one meter from the battery when the switch was closed. Which explanation best fits?
  • A. Sound from the battery traveled along the wires.
  • B. Electric current carried energy through the connected wires.
  • C. Light from the switch carried energy to the buzzer.
  • D. Warm air from the battery traveled to the buzzer.
2.
Select the two observations that together support the claim that sound energy traveled from the buzzer to Imani.

Imani heard buzzing across the sandbox when the switch was closed.The class placed its equipment on a dry board.The battery was one meter from the buzzer.Imani stopped hearing buzzing when the switch was opened.The card remained in shade during the mirror test.

3.
The switch is closed. A student removes one wire from the battery but leaves the battery beside the equipment. What should happen?
  • A. The buzz should get louder because the wire path is shorter.
  • B. The buzz should continue because the battery is still nearby.
  • C. The buzz should continue because the switch is still closed.
  • D. The buzz should stop because the current's path is broken.
4.
The class next wants to test whether the buzz sounds quieter farther away. Which plan makes the fairest comparison?
  • A. Keep the buzzer setting fixed and have Imani listen at two distances.
  • B. Lower the buzzer setting and have Imani listen farther away.
  • C. Keep Imani in one place and change the buzzer setting.
  • D. Replace the buzzer and have a different person listen farther away.
5.
Trace the energy path from the battery to Imani. Name two ways energy moved and use an observation to support each part of the path.

Follow the Bright Patch

Use the mirror observations. Think about the path between the sunny edge and the shaded card.

6.
The mirror is aimed at the card, and the cardboard is behind the card. A student turns the mirror face down. What is most likely to happen?
  • A. The patch will brighten because the cardboard is behind the card.
  • B. The patch will remain because the card has already received light.
  • C. The patch will disappear because the mirror no longer sends light there.
  • D. The patch will move to the cardboard because it is behind the card.
7.
A student says, "The card's bright patch came from sunlight reaching it directly, not from the mirror." Which comparison best challenges that claim?
  • A. The mirror was in sunshine while the equipment board stayed dry.
  • B. The shaded card gained and lost its patch when the mirror was turned.
  • C. The card was white while the cardboard was a different color.
  • D. The mirror and card were one meter apart throughout the test.
8.
Why did moving the cardboard from between the mirror and card to behind the card bring the patch back?
  • A. The cardboard supplied extra light when it was behind the card.
  • B. The card stored light while the cardboard was in front of it.
  • C. The cardboard warmed the card enough to make a bright patch.
  • D. The cardboard stopped blocking the light traveling to the card.

Explain the Sand Temperatures

All three sand samples started at 26°C. Compare the graph with the steps of the cold-pack test.

Class Results: Sand After Eight Minutes0481216202428On cold packFoam over packNo cold packTray setupSand temperature (°C)
9.

After eight minutes, how many degrees cooler was the sand directly on a cold pack than the sand above the foam?  °C

10.
Why did the class use the same amount and depth of sand in each tray?
  • A. To make each tray reach the cold pack's temperature in eight minutes.
  • B. To make each sample lose the same amount of heat during the test.
  • C. To compare the setups without also changing the sand samples.
  • D. To make the tray without a pack become cooler than the other trays.
11.
Which direction of heat transfer best explains the sand cooling from 26°C to 20°C?
  • A. From the 8°C pack through the tray into the warmer sand.
  • B. From the 26°C air into the sand as the sand became cooler.
  • C. From the shaded board into the sand directly above the pack.
  • D. From the warmer sand through the tray into the colder pack.
12.
The adult removes the cold pack from under the 20°C sand. The tray stays in the 26°C air. What is most likely to happen over time?
  • A. The sand will warm toward 26°C as it receives heat from its surroundings.
  • B. The sand will cool toward 8°C because that was the pack's temperature.
  • C. The sand will stay near 20°C because the tray is still in shade.
  • D. The sand will warm far above 26°C because the cold pack is gone.
13.
The class repeats the direct-contact test, but both the sand and the sealed pack begin at 26°C. The air is also 26°C. What result is most likely after eight minutes?
  • A. The sand will drop near 20°C because it touches a pack.
  • B. The sand will stay near 26°C because there is little temperature difference.
  • C. The sand will drop near 8°C because the pack is sealed.
  • D. The sand will rise well above 26°C because it touches plastic.
14.
A student claims, "The foam slowed heat transfer from the sand to the cold pack." Does the evidence support this claim? Use the starting temperature and both cold-pack results to explain.