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Matter Lab 6-8 / Week 03 / Wednesday
3/6
Week 03 · Heat, Temperature and Changing State

Wednesday

Bench Lab: The ice melt race
// Faster particles, flowing heat and the points where matter changes
⏱ about 20 min

Wednesday: Bench Lab: The Ice Melt Race

Rocket has three ice cubes lined up on three plates. "Sun, shade and the coolest corner of the house," he says.

"Are they the same size?" Raven asks. Rocket looks closer. One is clearly bigger. "Oops."

He trades it for a matching cube from the same tray. "Now it is fair."

Nova hovers over the plates, her light steady. "What are you changing on purpose?" she asks. "And what are you keeping the same?"

"Changing the spot," Rocket says. "Keeping the cube size, the plate and the start time the same."

"And what are you measuring?" Raven asks. "How long each one takes to melt," he says, starting the timer.

Raven writes three columns in the Bench Log: Spot, Start time, Melted at.

Your mission

Today you plan and run an investigation: in which spot does an ice cube melt fastest, and why?

A fair test changes one thing on purpose. Here, that is the spot. Everything else stays the same.

The thing you change is called the independent variable. The thing you measure, the time to melt, is the dependent variable.

The things you keep the same, such as cube size and plate type, are called controls.

If you have a thermometer, you will also watch a cup of water. You will record how its temperature changes as ice melts in it.

  • Three ice cubes of the same size from the same tray
  • Three matching plates or saucers
  • A timer or clock
  • A cup of tap water and a kitchen or room thermometer, if your family has one
  • A towel for spills
  • Your Bench Log
Safety first
Ice comes straight from the freezer. Hold cubes with a towel if your fingers get cold.
Warm tap water is the warmest thing you use. A grown-up handles any kettle, stove or microwave.
Choose spots that are safe to reach. Never put a plate on a stove, a heater or a windowsill above a drop.
Nothing goes in the mouth. Wipe up puddles right away and wash your hands when the lab is done.
  1. Pick three spots: a sunny or warm spot, a room temperature spot and the coolest spot you can find.
  2. Write your prediction in the Bench Log: which spot will melt the cube first, and which last?
  3. Put one plate in each spot. Place one cube on each plate at the same moment and write the start time.
  4. Check every five minutes. Write what you see: cube, half cube, sliver or puddle.
  5. Write the time when each cube is completely melted.
  6. If you have a thermometer, read the temperature of a cup of tap water. Add an ice cube and read it again every two minutes.
  7. Pour the water down the sink and dry your Bench.
PREDICT BEFORE YOU TIME
  • Read the question.
  • Tap your answer.
Which spot will melt the ice cube fastest?
In this test, what is the independent variable, the thing you change on purpose?
An ice cube is added to a cup of tap water. What happens to the water temperature?
SpotPrediction (1st, 2nd, 3rd)Start timeCompletely melted atMinutes to melt
Warm or sunny spot
Room temperature spot
Coolest spot
Time (minutes)Water temperatureWhat the ice looks like
0 (before the ice)
2
4
6

What the lab shows

Heat flowed from the warmer air into each ice cube. Where the air was warmer, more energy flowed in, and the cube melted sooner.

As the ice melted, its temperature did not rise. All the energy going in was used to break the particles loose from their fixed positions.

In the cup, heat flowed from the warmer water into the colder ice. The water lost thermal energy, so its temperature went down.

A fair test with controls lets you say the spot, and nothing else, caused the difference.

What the lab showsTrue or false?
The cube in the warmest spot melted first.?
Using cubes of different sizes would still be a fair test.?
The time to melt is the dependent variable.?
The water in the cup warmed up when ice was added.?
WHY THIS EXERCISEPlanning a fair test with variables and controls is exactly what this week's standard asks you to do.
The things kept the same in a fair test are called ____.
Heat flowed from the warmer air into the colder ____.
Draw your three plates in their spots with arrows showing heat flowing from the air into each ice cube.

Excellent investigation. Tomorrow you will read the melting and boiling points of real substances and see how yours compares.

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