An educated prediction is just a guess with its reasons showing. Build one here, watch it grow, run a check-up on it — and you'll never be stuck on "what do I write?" again.
Plant the ideaA hypothesis is an educated prediction shaped like a tiny story: if I change one thing, then this will happen, because here's the reason why.
Notice the shape. It isn't a wild guess, and it isn't a fact you already know — it sits right in between: a prediction you can actually test, with the thinking behind it on full display.
The word itself is a clue. "Hypothesis" comes from old Greek words meaning roughly "to place underneath." That's exactly its job: it's the idea you slide underneath an experiment, like a foundation under a house. The experiment then sits on top and presses down — and either your foundation holds, or it cracks. Both outcomes teach you something.
Here's why scientists write the hypothesis before they touch any equipment. Once you've said out loud "I think this will happen, and here's why," you've made a promise to yourself. You can't quietly change your mind later and pretend you always expected whatever the experiment showed. Writing it down first is how science keeps you honest — it stops you from fooling the one person it's easiest to fool, which is you.
Spin the three dropdowns. Each pick drops into the sentence, lights up one part of the recipe, and feeds your idea so it sprouts. Try mixing parts from different experiments — the plant will tell you when the story stops making sense.
If I change one thing, then a result happens, because the reason why.
Pick a change, a result, and a reason to grow your hypothesis.
Did you notice what happened when you mixed parts from different experiments? The sentence still reads like English — "if I heat the water, then the toy car rolls faster, because plants use light to make food" — but it's nonsense. The change, the prediction, and the reason have to be about the same thing. That's the quiet rule hiding inside every good hypothesis: all three parts must tell one connected story.
Try this: shuffle a fresh hypothesis, then read it aloud as if you're explaining it to a friend. If you can't say it without stumbling, that's usually a sign one of the three parts doesn't fit — exactly what the drooping sprout is warning you about.
Every hypothesis hides the same three pieces. Once you can name them, you can write one about almost anything — a plant on your windowsill, a recipe, a bike that keeps squeaking.
Read those three back to yourself and you'll spot the rhythm: I do something → I expect something → here's why. Lock that rhythm into your head and a blank page stops being scary. You're not inventing from nothing; you're just filling three slots, in order.
Anyone can guess that sugar dissolves faster in hot water. A hypothesis goes one step further and says why. Here's the reason made visible: temperature is really just how fast the tiny particles are jiggling. Crank up the heat and watch them speed up — and watch the sugar disappear faster.
Warm water: the particles bustle along, knocking sugar loose at a steady pace.
The faster the particles bump into the sugar, the quicker it breaks apart and dissolves. That little chain of cause and effect — heat → faster particles → faster dissolving — is exactly what your "because" is pointing at. Without it, you'd only have half a sentence.
The "because" earns its keep in two ways. First, it connects your prediction to what you already know, so your idea isn't floating in mid-air — it's tied to real science you can build on. Second, it gives you something specific to check. If the sugar dissolves faster but you discover the real reason was that you stirred harder, your "because" was wrong — and finding that out is a genuine discovery, not a failure.
The honest truth: your "because" is allowed to be wrong. A hypothesis is your best current guess about why, not a fact carved in stone. The whole point of the experiment is to find out whether your reason holds up. A wrong "because" that you tested carefully still beats a right answer you simply assumed.
Behind every hypothesis is an experiment, and behind every experiment are variables — the things that could change. There are exactly three kinds, and a good hypothesis points straight at two of them. Picture a control panel: one dial you turn, one needle that reacts, and a row of locked switches you promise not to touch.
Why does locking the rest matter so much? Imagine you give one bean plant more sunlight and more water and it grows taller. Was it the sun or the water? You'll never know — you changed two dials at once, so the needle's answer is muddled. Change one thing, keep the rest locked, and the experiment gives you a clean answer. Your hypothesis names the dial (the change) and the needle (the prediction); the locked switches are the promise you make to keep the test fair.
A lot of people carry around half-right ideas about hypotheses. Let's swap each one for the real version, because the myths are exactly what trips people up in exams and lab reports.
"A hypothesis is just a guess."
It's an educated prediction with a reason attached. A guess says "the ice will melt." A hypothesis says "the ice will melt faster if I add salt, because salt lowers the temperature water can stay frozen at." The reasoning is the whole difference.
"A good hypothesis has to turn out right."
A hypothesis that gets disproved is still great science. You haven't failed — you've learned that the world doesn't work the way you thought, which is genuinely useful. Many famous discoveries began with a hypothesis that fell apart and pointed somewhere more interesting.
"You can prove a hypothesis true forever."
Experiments can support a hypothesis (the evidence agrees) or refute it (the evidence disagrees) — but science never slams the door shut. There's always room for new evidence to change the story later. "Supported so far" is the strongest, most honest thing a careful scientist will say.
"A hypothesis and a theory are the same thing."
A hypothesis is a single testable idea. A scientific theory is a big, well-tested explanation that has survived many experiments — like the theory of how diseases spread. Theories are built from mountains of supported hypotheses; one is the brick, the other is the building.
There's one more trap worth naming. A hypothesis has to be falsifiable — that's a long word for a simple idea: there has to be some result that would prove it wrong. "My plant grows because it wants to" can't be tested, because nothing could ever disprove it. "My plant grows taller in more light" can be tested — if it doesn't, you've got your answer. If no possible result could ever prove your idea wrong, it isn't a hypothesis yet.
Tap a sentence below and the checker examines it like a doctor with a stethoscope — does it name a change you control? Predict something measurable? Give a reason? Could it ever be proven wrong? Watch which boxes light up green, and which ones it flags.
Pick a statement above to run the check.
Health: waiting for a patient…
See the pattern? The statements that fail almost always fail in the same predictable spots — a missing "because," a prediction you can't actually measure, or a claim nothing could ever disprove. Once you know the four checks, you can run them on your own writing in your head before you ever hand it in.
Theory sticks best when you see it work on real questions. Here are five hypotheses from different corners of science — tap any one to see its three parts laid out, plus how you'd actually test it and what result would support or sink it.
"If I give a bean plant more hours of sunlight a day, then it will grow taller, because plants use light to make their own food through photosynthesis."
Hours of sunlight per day — the dial you turn. Try 4 hours versus 8 hours.
The plant's height in centimetres, measured at the same time each day with a ruler.
Light is the energy source for photosynthesis, so more light should mean more food and more growth.
Same seed type, pot, soil, and water for every plant — only the light changes.
Supported if the 8-hour plants end up clearly taller. Refuted if extra light makes no difference (or scorches them) — which would send you hunting for a better reason.
"If I sprinkle salt on an icy step, then the ice will melt sooner, because salt lowers the temperature at which water can stay frozen."
Salt or no salt — two identical ice cubes, one sprinkled, one left plain.
The time it takes each cube to fully melt, timed with a clock.
Salt mixed into ice lowers its freezing point, so the ice can't stay solid at the same temperature.
Same size cubes, same room, same surface — only the salt differs.
Supported if the salted cube melts noticeably faster. Refuted if both melt at the same rate.
"If I make a pendulum's string longer, then it will take more time to complete one swing, because a longer arm has farther to travel on each pass."
The length of the string — try 20 cm, then 40 cm, then 60 cm.
The time for one full swing (time ten swings and divide by ten for accuracy).
A longer pendulum sweeps a wider arc, so each swing covers more distance and takes longer.
Same weight on the end, same starting angle, same push (or no push) every time.
Supported if longer strings give slower swings — which they reliably do. A neat case where the prediction holds and the "because" is on the right track.
"If I store a slice of bread somewhere warm, then it will grow mould sooner, because warmth helps the mould's tiny spores grow and spread faster."
Temperature — one slice on a warm windowsill, one in the fridge.
How many days until the first fuzzy spot appears, checked once a day.
Mould is a living thing, and like most living things it grows faster in warmth than in cold.
Same loaf, same size slice, both in sealed bags — only the temperature changes. (An adult should help, and don't open the mouldy bags.)
Supported if the warm slice moulds first. Refuted if the fridge slice somehow moulds sooner — surprising, and worth a closer look.
"If I jog for five minutes before reaching for my toes, then I'll be able to reach farther, because warming up loosens the muscles so they stretch more easily."
Warmed up or not — measure your reach cold, then again after a five-minute jog.
How far past your toes your fingers reach, in centimetres, using a measuring tape.
Gentle movement warms the muscles, and warm muscles stretch a little farther than cold ones.
Same stretch, same time of day, measured the same way each time.
Supported if your warmed-up reach is longer. A hypothesis you can test on yourself in ten minutes — which is part of what makes science feel real.
Notice how every single one follows the same skeleton: name the dial, name what you'll measure, give the reason, then say what result would settle it. Different topics, identical bones. That's the trick — the shape never changes, only the words you pour into it.
This isn't only a lab-report skill. The if/then/because reflex is how careful thinkers chase down answers in all sorts of jobs — and in everyday life, probably more often than you'd guess.
A diagnosis is a hypothesis: "if it's the flu, then a test will show the virus, because your symptoms match it." The test either supports the guess or sends the doctor back to thinking.
Every theory of a case is a hypothesis waiting for evidence: "if she did it, then her fingerprints would be on the door, because she had to open it to get in."
They run "A/B tests": "if we make the button blue, then more people will tap it, because blue stands out against the page." Then they measure the taps.
"If the bike light won't turn on because the battery's dead, then a fresh battery will fix it." Swap it, test it — that's a hypothesis you live by without noticing.
Once the if/then/because shape clicks, you start hearing it everywhere — in the kitchen, on the sports field, in an argument with a friend about why the WiFi keeps dropping. That's the real prize here. You're not just learning to fill in a worksheet; you're learning a way of thinking that quietly makes you better at figuring out the world.
Each card makes a claim. Decide: does it have all three parts — especially a reason — and could it actually be tested? Or is it only a hunch? Tap your answer.
"If I keep this plant in the dark, then its leaves will turn pale, because without light it can't make the green stuff it needs."
"Chocolate is the best ice-cream flavour."
"The taller candle will burn out first."
"If I roll the ball on carpet, then it stops sooner, because the rough carpet rubs against it with more friction."
"If I play music to my plant, then something interesting will happen, because plants enjoy company."
"If I drop the tablet into warmer water, then it will fizz away faster, because warmth makes the reaction happen more quickly."
Next time a blank page asks you for a hypothesis, don't reach for the perfect answer. Reach for the shape.
Name the one thing you'll change on purpose — your dial.
Say what you think will happen, in something you can measure.
Add the reason — that's what makes it science, not a guess.