Teach lesson
Did the thermometer get stuck?
A 26-minute science mission on the core route, or about 31 minutes with the optional graph: use a real run to investigate why a thermometer's reading barely changes while ice is being heated.
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Learning Outcomes
Use a low-heat run in the remote laboratory and observe its two cameras.
Put four moments of the process in order and recognise how the state and amount of ice change.
Explain in words and with energy arrows why the temperature changes very little during one part of the heating.
In the extension for ages 12–13, plot only four temperature–time points and identify the almost flat stretch.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
1 · A beaker of ice and a surprise
7 min
In class, your teacher will present this first part aloud while you look at the images. If you are working on your own, read it without trying to memorise all the equipment names at once: you only need to recognise what each camera shows.
Today you are going to work from your computer with a real run carried out in a laboratory: a beaker of ice and water was gently heated while two cameras recorded what happened. In TEACH you will be able to select that configuration and watch the recording. Why? To find out why the temperature hardly went up during part of the run.
Your job will be to select the recording of gentle heating and watch two things: what happens inside the beaker and how the temperature changes. When we heat something very cold, we expect its temperature to go up. That is why the result of that earlier run is so striking. Before you try to explain it, get to know the parts of the experiment and what you will be able to see.
Two metal rods come down into the beaker from above, and they have different jobs:
- The heater is the rod that can deliver energy to the contents of the beaker when it is switched on.
- The probe measures the temperature and sends the result to a digital thermometer. The probe is the part inside the beaker; the thermometer is the display where the number appears.
When you open the laboratory, you will be able to watch the same experiment from two cameras. Think of them as two witnesses who tell different parts of the story:
- The process camera looks at the beaker. It lets you follow what is happening to the ice and the water around the two rods.
- The thermometer camera looks at the display connected to the probe. It lets you know what temperature is being measured at each moment.
To solve the mystery you will need to connect what you see in the beaker with what the display shows.
The scene at the start
This is the view from the process camera at the beginning of a real run. The beaker looks whitish and cloudy: the contents make it hard to see the rods.
Now you know the setting. Next, look at the piece of data that started the investigation. We will call this opening run the shared case.
In that run, the gentlest mode was selected, Heating · Low heat. Five seconds after the start, the thermometer camera recorded this reading:
Thermometer camera · 5 seconds
The thermometer shows 0.5 °C.
The run continued in the same mode. Twenty more seconds went by. This was the new reading:
The same camera · 25 seconds
Now the thermometer shows 0.6 °C.
20 seconds passed between one image and the other, but the reading went up by only 0.1 °C. When you hear the word "heating", it would be natural to expect the temperature to rise clearly. And yet the reading barely moved: it stayed very close to zero.
That is where your mission begins. First you will choose an initial explanation. Then you will configure one recording of a real low-heat run and collect two clues of your own: one from the beaker and one from the thermometer. You will compare them with four moments from another real case. At the end you will rebuild the case as a short four-scene visual story.
You don't have to get it right the first time: a scientific hypothesis is an idea that we compare with what we actually observe. Choose the one that seems most convincing to you now, before moving on to the investigation.
Your first hypothesis
What do you think is the best explanation for the temperature barely changing between 5 s and 25 s?
Before you open the laboratory, decide what you will check: whether the ice changes and whether the thermometer number changes later. You do not need to write another answer yet; these will be the two short clues from your own run.
2 · A single run: low heat
8 min
Now investigate the case with one recording of a real low-heat run. This observation is the main part of the mission: you will need one clue from each camera to back up your explanation. You do not need to calculate rates or draw a graph.
Open the laboratory and follow the journey of the ice
Open the laboratory from this block.
From the introduction, continue to 2 · Configuration.
Choose Heating and Low heat. If that setting is already shown, leave it as it is. Do not use high heat or cooling.
Go into 3 · Observation. Playback will start automatically; do not look for another start button.
You will see the process camera (the beaker) and the thermometer camera together. Watch both without changing views.
During roughly the first 40 s, note one short clue from each camera at the same moment: write an approximate time, what you can see in the ice and water, and what the thermometer shows then.
Later, at roughly 60 s to 90 s in your video player, look at the thermometer camera again. Note an approximate reading, or say whether it is still almost the same or has clearly gone up. Both results are valid: write what happens in your recording. Keep the speed at 1×.
As soon as you have both clues, press Leave now to return to TEACH. The player may show a total duration of nearly 29 minutes, but you do not need to watch it all. After about 90 s, note whether the reading is still almost the same or has gone up, then leave. There is no need to repeat the run or make up a value you did not see.
If you are working in pairs, one person can be the beaker detective and the other the thermometer detective. Share both clues before you leave.
If you find it hard to make out the ice, to read the display, or to write while you are watching, ask a classmate or the teacher to describe one frame aloud and read the temperature. You can dictate your two clues to someone else. What matters is how you connect the observations; how well you can see and how quickly you write are not being assessed.
Clue 1 · Both cameras at the start
In your run, during roughly the first 40 s, what could you see in the beaker and what did the thermometer show at that moment? Write down an approximate time and one very short clue from each camera.
Clue 2 · The thermometer later
Later, at roughly 60 s to 90 s and before pressing Leave now, what reading did you see in your run? If you couldn't read the exact number, write whether the temperature was still almost the same or had clearly gone up.
3 · Compare with the shared case
5 min
Your run has already given you two clues. Now return to the shared case from the opening, which is a different real run from your recording. Its four cards—each one an image with its time and temperature—let the whole class use the same reference even when each recording shows different timings. Compare the order of the changes, not whether both clocks show the same time. The cards do not replace your own observations: in your closing sentence you will have to use the clue from the beaker and the clue from the thermometer from your own run.
The shared readings are: 5 s → 0.5 °C; 25 s → 0.6 °C; 45 s → 3.2 °C; 70 s → 14.3 °C. The four images in the next question show the beaker at those same moments.
Choose the visual clue
Compare the four frames and their readings. Look for an intermediate moment: the contents have clearly changed since 5 s, but the thermometer is still near 0 °C. There is also more ice left than at 45 s. Which image-and-reading pair is the best evidence?
Fill in the four rows as a minimum record of the shared case. In each one, choose the description that best matches its card. A description may be used more than once. Do not add new rows.
Minimum record of clues
Fill in exactly the four rows of the shared case. The time and the temperature are already fixed; choose only what can be seen in the beaker.
| Time s | Temperature °C | What can be seen |
|---|---|---|
4 · Create “The journey of the ice”
6 min
Use your shared-case table to turn its four scenes into a mini science story called The journey of the ice. We are only giving you the time and the temperature for each scene:
1. 5 s · 0.5 °C
2. 25 s · 0.6 °C
3. 45 s · 3.2 °C
4. 70 s · 14.3 °C
Now add the scientific meaning yourself in the answer box. For each scene:
- reuse the state phrase you already chose in the table;
- add → energy and just a few words about its effect: changes state, raises temperature, or both.
You do not need to write four full sentences: one short line per scene is enough. You can type or dictate them. You are not being marked on drawing skill or perfect spelling, but on your interpretation of the evidence.
Hand in four lines and two closing sentences
Write or dictate one short line per scene using this pattern: "state or amount of ice → energy: effect". Then add only two sentences:
1. "My run: at the start I saw… and the thermometer showed…; later the thermometer…"
2. "I think the temperature hardly went up between 5 s and 25 s because…; my run matches / does not quite match the shared case because…"
You do not need to repeat the work on paper or write another conclusion.
Optional: photo of The journey of the ice
If you would like to turn the four sentences into drawings, you can do that on paper and upload a clear photo. It should show the four times and temperatures, your interpretation of the state of the water, and the energy arrows. This is an optional creative extension: the answer box above is already the complete submission.
Extension for ages 12–13 · Four points and a circle
5 min
Use only these four points: 5 s → 0.5 °C; 25 s → 0.6 °C; 45 s → 3.2 °C; and 70 s → 14.3 °C.
On squared paper or in a graphing tool:
1. put time (s) on the horizontal axis and temperature (°C) on the vertical one;
2. plot the four points and join them in order;
3. draw a circle around the stretch between 5 s and 25 s;
4. write a short label next to the circle that explains in your own words what was happening there.
Do not calculate rates: plot only those four points.
The lines only help you follow the order: with four points we don't know exactly what happened between one and the next.
If making a graph is a barrier, use the no-graph route in the next question: put the four pairs in order and explain the 5–25 s stretch in words or by dictation.
Optional: photo of the four-point graph
If you can, upload a photo or an image of the graph with its two axes, units, four points and the almost flat stretch circled. If you can't upload it, show it to your teacher on paper. As an accessible alternative, write or dictate the four time–temperature pairs in order and identify the 5–25 s stretch in the next question.
What the stretch means
Explain in your own words what you think the 5–25 s stretch means—the one you circled, if you made the graph. If you did not make, upload or show the graph, first write the four time–temperature pairs in order here and then interpret that stretch.
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