The Case of the Vanishing Chalk

A classroom mystery that teaches observation, questions, hypotheses, testing, and careful reporting — the scientific method in a story.

Opening

Miss Amaka’s classroom was the kind of room where rulers lived in a mug, and every chair had a secret nickname. One bright Tuesday, as the bell finished its cheerful ring, something small and strange happened: Chalk started to vanish from the board. Not little dust — whole sticks of chalk disappeared between lessons.

It began with a shrug. "Probably Tunde," said one of the older pupils. Another suggested the cat in the compound had a fondness for chalk (unlikely but very funny). Miss Amaka raised her hand and asked the class to notice, not jump to reasons. "If we want to know what happened, we'll need to watch carefully and ask better questions," she said. "Let's treat this like science."

This is the moment where a story becomes an investigation. The class discovered they could turn an odd problem into a lesson about observing, wondering, and testing ideas — the same skills real scientists use when they do research.

Teacher tip: Use the story to frame curiosity. Encourage students to treat the missing-chalk problem as a safe, small mystery they can solve together.

The Mystery Begins

At 9:00 AM the board had five sticks of chalk in the pot. By 10:30 two were missing. At midday they were down to one. The janitor laughed and said the cleaners sometimes tidy up too carefully — but he had not touched the classroom that morning.

Amaka asked the class to write down exactly when they had last seen the chalk and where they had left it. Small notebooks opened and scribble-notes multiplied. The class used different colored pens so they could see patterns in handwriting if necessary. It felt serious and slightly secretive: the handwriting looked like clues.

Next, Miss Amaka asked them to list everything that could cause chalk to disappear. The answers were a mixture of playful and sensible: "someone took it", "it melted in the sun", "the chalk jumped", "it dissolved in water", "the cleaning cloth hid it", "it was used to write and the pieces fell".

Instead of picking the funniest idea first, Miss Amaka praised careful observation: "Every idea is welcome, but the best ideas are ones we can try and test. We'll use steps that help us find out which idea fits the facts."

Observe Closely — The First Step

Observation is the scientist's first tool. It uses the five senses (sight, hearing, touch, smell, taste — but not taste in our classroom experiments!). The class learned to write down exact observations without adding reasons. That is, they wrote: "Chalk count 5 at 8:50; chalk count 3 at 10:15." rather than "Someone stole chalk."

For two days the class kept a chalk-log. One child volunteered to be the "Chalk Watcher" for each period. They recorded where the chalk was kept, who used it, and any stray pieces on the floor. They also checked pockets during break (only with permission) and asked the janitor if he had borrowed any.

Important discovery: the chalk seemed to vanish even when the room was locked during break times. This fact began to change which ideas were plausible. If chalk went missing while the room was secured, maybe something about the chalk itself or the environment was causing the disappearance.

Make a Hypothesis — An Idea to Test

A hypothesis is a testable idea. The class generated several hypotheses together, keeping them short and clear:

• H1: Someone is taking the chalk home.
• H2: Chalk is dissolving because of humidity (high moisture).
• H3: Chalk is breaking into dust and slipping into cracks or under the board.
• H4: The janitor removes old chalk during cleaning.

Miss Amaka asked the class to choose which hypothesis to test first and why. They picked H2 and H3 because these were easy to test with simple classroom tools (plastic bags, small trays, a magnifying lens, and a ruler).

Design an Experiment — Fair and Simple

Good experiments keep variables controlled. That means changing one thing at a time while keeping other conditions the same. The class designed two short tests:

Test for H2 (humidity): Place two identical sticks of chalk in separate sealed plastic bags — one with a small damp sponge placed outside the bag to raise local humidity near the bag (but not touching the chalk), and one with a dry tissue. Place both bags on the same shelf. Check both every hour and record any visible changes.

Test for H3 (crumbs/hidden dust): Set a tray under the board, place three small chalk sticks on the tray, and draw on the board for twenty minutes to see whether tiny chips fall into the tray or slide under the ledge. Use a magnifying glass to inspect the tray contents.

The class wrote the experimental plan on a big chart and assigned roles: measurer, recorder, timer, and photographer. This way the experiment was fair and everyone had a job.

Collect Data — Watch and Record

Data are the facts you collect during an experiment. For the humidity test students photographed the chalk in each bag hourly and wrote short notes: "no change", "surface more crumbly", "small cracks". For the tray test they weighed the tray before and after (use a simple kitchen scale if available) and examined any dust under magnification.

After two days the group noted that the chalk in the 'humid' bag had tiny surface fissures and a slightly softer surface — but not full dissolving. In the tray test they found a small number of chalk particles, but not enough to account for whole sticks going missing. That pointed away from chalk simply crumbling in the classroom to explain the vanishing problem.

Miss Amaka reminded students: good scientists change their ideas in the light of new data. It was also time to test H1 and H4 more carefully using observational controls.

Analyze & Conclude — What Does the Evidence Say?

Analyzing means looking at the data and asking what they support and what they contradict. The class compared counts of missing chalk, photos, and the tray weights. The humidity test showed minor surface changes but not disappearance; the tray test showed crumbs but insufficient loss. That suggested H2 and H3 were partial contributors but not whole explanations.

To test H1 and H4 (someone taking chalk or the janitor removing it), the class used a non-confrontational observational test: they made simple paper "chalk tags" — a thin strip looped around a stick — with a unique color code and asked permission to leave the classroom door slightly ajar for short intervals while one student watched from the corridor (with consent and supervision). They were interested in whether people entering would disturb the chalk or move it.

After three sessions, they observed a pattern: during break times when the door was left ajar for observation, a small group of ants from a crack in the wall were carrying teeny particles of chalk to a nest inside the wall cavity. The particles were tiny — enough to dull many sticks over time, but not to make full sticks disappear overnight. While useful, this alone still did not explain whole sticks going missing.

On the fourth observation, the class discovered that a cleaning cloth habitually used to wipe the board had a secret — small slips of chalk often got caught in the pockets of a cloth bucket stored behind the teacher's desk. When the bucket was emptied, the cloths were taken to a cleaning room where dust was shaken out. A student who volunteered to help in the cleaning store later reported that whole sticks sometimes fell into a loosish box under the sink. The "missing" chalk had been collected there accidentally during cleaning rounds by the cleaner.

With the evidence in hand, the class concluded: multiple factors contributed to the apparent vanishing — humidity causing slow surface loss, ants carrying tiny particles, and cleaning routines that moved intact sticks into storage. None alone explained everything, but together they explained the pattern of missing chalk.

Extension Activities & Teaching Notes

Use this mystery to explore many science skills:

• Observation practice: Create a "chalking" station and ask children to record changes every 30 minutes for a day.
• Variables & controls: Test humidity, heat, or pressure using simple controlled setups.
• Recording and reporting: Have students produce a poster summarizing their hypothesis, method, data, and conclusion.
• Ethics and care: Discuss respectful observation — asking permission before checking pockets or rooms — and the difference between observing and accusing.

Assessment ideas: short lab reports, group presentations, and reflective journals about what surprised them and how scientists change ideas when new evidence appears.

Educational Videos (AdSense-friendly embeds)

Below are short, reputable videos lesson.They are from established educational channels (SciShow Kids and kid-science explainers) and are embedded without autoplay.

Scientific Method for Kids — an easy steps explainer to introduce observation, hypothesis, test, data, conclusion. (Source: educational kid explainer). 0

Short summary (add your own 1–3 sentences):

Steps of the Scientific Method — short kid-friendly breakdown of observation, hypothesis, testing, data and conclusion. 1

Short summary (add your own 1–3 sentences):

SciShow Kids: Problem solving and doing simple investigations — great for showing scientists at work. 2

Short summary (add your own 1–3 sentences):

SciShow Kids: Field observations and hands-on exploration for kids — helps build observation skills. 3

Short summary (add your own 1–3 sentences):

Final Notes — Teaching with Care

This mystery teaches children important science practices: to notice details, make careful plans, test fairly, and explain conclusions using evidence. It also teaches patience and ethical observation: ask before you search someone’s pocket; treat others with respect when collecting data.

© Edwin Ogie Library — Use for non-commercial educational purposes welcome. For reuse contact edwinogielibrary@gmail.com.