Scientific Inquiry: Questions, Evidence & Explanations — Print · Grade 6 Science

Scientific Inquiry: Questions, Evidence & Explanations

Learning goals

I can tell an investigable question from one science cannot settle.
I can separate an observation from an inference drawn out of it.
I can explain why an explanation has to say what would count against it.

Readings for this unit

A Neat Result Is Not Yet an Explanation

Before this unit

Read the chapter opening and the named observation or diagram. Clarify one word or unit that blocks understanding. Recall the relevant earlier measurement, matter, or energy idea.

Study the unit across three 35–45-minute class sessions. Use the worked examples after an attempt and the supplied records when actual equipment is not available.

In 1847 a doctor in Vienna named Ignaz Semmelweis noticed something that should not have been true. In one maternity ward of his hospital, run by doctors, about 18 in every 100 mothers died of childbed fever. In the next ward, run by midwives, the figure was about 2 in 100. Same building, same city, same year.

He did not start by guessing a cause. He started by listing differences between the wards and testing them one at a time, and he found one that mattered: the doctors came straight from dissecting bodies, and the midwives did not. When he made them wash their hands in a chlorine solution, deaths in his ward fell to around 1 in 100 within months.

That is the whole shape of scientific work in one story. An observation nobody can deny, a list of possible causes, a test that could have come out either way, and a measurement at the end. Notice too that he was ignored for twenty years, which is part of the story as well.

Build your understanding

Where this fits

This is the first lesson of the course and the one the others lean on. Everything that follows -- particles, circuits, plate boundaries, moon phases -- is an explanation somebody built out of evidence, and knowing how that is done is what lets you judge whether to believe it. The chapter after this covers how to measure the evidence.

Use three flexible 40-45-minute sessions: what makes a question investigable; observation against inference; building an explanation that can be tested, then the practice set, revision and the exit check. Workshop, review, quiz and exams have separate time.

Part 1 · Which questions science can answer

Science can settle a question only when some possible result would count against the answer. “Does a heavier ball fall faster than a light one?” is answerable: drop a 1 kg ball and a 5 kg ball from the same height and time them. They land together, which is not what most people expect, and that result would have refuted the opposite claim. “Is this piece of music beautiful?” is not answerable this way, not because the question is silly but because no measurement could decide it. Many real questions sit in between and can be made answerable by sharpening them. “Is this water safe?” cannot be measured as written, but “does this water contain more than 10 mg of nitrate per litre?” can be, because a test either exceeds that number or it does not. Turning a vague question into a measurable one is most of the work of planning an investigation.

The test to apply is always the same, and you can use it on anything you read. Ask what result would make the person making the claim change their mind. If they can name one, you are looking at a scientific claim, and you can go and check. If no possible evidence would shift them, the claim may still be true or important, but it is not something science has the tools to settle, and dressing it up in scientific language does not change that. This matters well outside a laboratory. Advertisements, headlines and arguments online all borrow the look of scientific claims, and the quickest way to tell the difference is to ask what evidence the person would accept against themselves. A claim with an answer ready for every possible result is not a strong claim; it has stopped being about evidence at all.

The test is whether some result could contradict it. Naming the measurement and the time period is what turns an interesting thought into something a learner can actually find out on a windowsill.

Pause and explain

What makes a question investigable?

Check your reasoning after answering

That some possible result would count against the answer. If you can name a measurement whose outcome would make you abandon the claim, the claim can be tested and checked by anyone else. If no result would change your mind, there is nothing for evidence to do, however reasonable the idea sounds.

Part 2 · What you saw and what you worked out

An observation is what reaches your senses or your instrument. An inference is the explanation you build on top of it. “The thermometer in the sun reads 31 °C and the one in the shade reads 24 °C” is an observation. “Sunlight heats the air” is an inference, and in this case a wrong one: sunlight is warming the thermometer itself, not the air around it, which is exactly why weather stations keep thermometers in a shaded, ventilated box. Instruments do not settle the problem by themselves, because an instrument always reports something narrower than you assume. A thermometer reports its own temperature, a light sensor reports the light reaching its surface, and a balance reports the force pushing down on it. Knowing exactly what a device measures is what tells you which inferences its reading can support.

Keeping the two apart is the single most useful habit in this course, because almost every mistake you will meet is an inference being reported as though it were an observation. When you write up an investigation, put what you measured in one column and what you concluded in another. Anyone can check the first column. The second is where you can be argued with, and where a different explanation of the same numbers might turn out to fit better. A useful exercise is to take any conclusion from a textbook and hunt for the observation underneath it. Sometimes it is one measurement; far more often it is thousands, taken by different people with different instruments over decades. That gap between a one-line statement and the evidence behind it is where most of science actually lives.

Pause and explain

Why should an observation be recorded separately from an inference?

Check your reasoning after answering

Because they can be checked in different ways. Another person can repeat a measurement and get the same reading, so the record stands on its own. The explanation built on top of it may be wrong even when the reading is right, as with a thermometer in sunlight, and keeping it separate makes it possible to replace the explanation without discarding the data.

Part 3 · Evidence, and how much of it

One result is a start, not a finding. Semmelweis did not change hospital practice on the strength of one week; he tracked monthly death rates across years, which is why the drop from around 18 per 100 to about 1 per 100 was convincing rather than a run of luck. Numbers bounce around on their own, and the job of repeating a measurement is to find out how much of the change you are seeing is real. Repeating also gives you something no single reading can: the spread. Measure the same length five times and get 64, 65, 65, 66 and 65 mm, and that spread of about 2 mm is your honest uncertainty -- a difference smaller than it between two objects is not a difference you have actually detected. One measurement hands you a number with no way to judge it.

The amount of evidence a claim needs depends on what it would overturn. A claim that fits everything already known can rest on a modest result. A claim that would overturn a well-tested explanation needs evidence strong enough to also explain why everyone measuring before got a different answer. This is not stubbornness: a well-tested idea is one that has already survived many chances to fail, and that survival is itself evidence that has to be accounted for. There is a fair version of the opposite worry. Sometimes a well-tested idea is wrong and the evidence against it is brushed aside for far too long, which is exactly what happened here: Semmelweis's figures were sound and his explanation was right, and he was rejected for two decades partly because nobody had yet described germs. The rule is to weigh evidence, not to defend whatever is established.

Pause and explain

Why does a surprising claim need more evidence than an ordinary one?

Check your reasoning after answering

Because it has to account for the earlier measurements as well as its own. An idea that is already well tested has survived many opportunities to be shown wrong, and that record counts as evidence for it. Overturning it means explaining both your new result and why everyone who measured before found something different.

Part 4 · An explanation that could be wrong

A scientific explanation does three things: it accounts for the evidence you have, it says what mechanism produced it, and it makes a prediction about something you have not measured yet. Semmelweis's explanation had all three -- the doctors carried something from the dissection room, washing removed it, and therefore wards where nobody dissected should already have low rates. The midwives' ward was exactly that prediction, and it held. Compare that with an explanation that cannot fail. If someone says the deaths were caused by bad air, and then explains every low-death ward by saying its air happened to be better, nothing has been predicted and no result could ever count against it. Bad air was the accepted explanation at the time, which shows that being widely held is not the same as being testable.

The last part is what separates an explanation from a story that fits. Almost any set of facts can be explained after the event by something; the test is whether the explanation commits you to a claim about the next measurement. When you write your own explanations in this course, finish each one with the sentence “if this is right, then we should also find...”, and then go and look. Being wrong at that point is useful, which is a strange idea at first and the most important one here. Keep one more thing in mind while you do it. An explanation that turns out wrong is not wasted work provided the prediction was clear, because you now know something about the world you did not know before, and the next explanation has to account for it. Most of what is in this course was reached by somebody being specifically, usefully wrong first.

Pause and explain

Why must a scientific explanation predict something not yet measured?

Check your reasoning after answering

Because an explanation invented after the fact can always be made to fit what already happened. Committing to a result you have not seen gives the idea a genuine chance to fail, and surviving that is what makes it worth believing. An account that explains everything already known but predicts nothing new cannot be tested at all.

Apply the whole unit · Sort the claims

Three statements: (a) adding 10 g of salt to 100 mL of water raises its boiling point; (b) the blue mug keeps coffee warmer than the white one; (c) blue is a calming colour.

Your task

Decide which can be settled by measurement, say how, and explain the one that cannot.

What your response should show

Names a specific result that would falsify each testable claim
Describes a measurement with a quantity and a comparison
Explains the third case by the claim's wording, not by dismissing it
Keeps observations separate from the conclusions drawn from them

Response guidance — after your attempt

For each statement, name a result that would show it is false.
Describe the measurement you would take for the two that can be tested.
Explain what makes the third different, without calling it unimportant.

Statement (a) is investigable: boil 100 mL of pure water, record the temperature, repeat with 10 g of salt dissolved, and compare. A result of no change, or a lower temperature, would refute it; in fact the boiling point rises by roughly 1 °C. Statement (b) is investigable: fill both mugs with water at the same starting temperature, say 80 °C, leave them in the same room, and measure both after 20 minutes. If the blue mug is cooler, the claim fails. Statement (c) is different. People's reported feelings can be surveyed, and you could measure heart rate in a blue room against a white one, but the claim as written does not say what counts as calming, so no result would settle it until the word is defined. That is a limit of the question's wording rather than a judgement about whether colour matters to people.

Scientific references for this unit

Parent / teacher teaching notes

Begin with the literal observation, quantity, or diagram relationship. Ask the learner to explain why the evidence supports the claim, check a relevant unit or boundary, then discuss an alternative. The supplied numbers are illustrative, not real observations. A parent can read aloud and allow a spoken rehearsal before writing. Judge science and evidence rather than political, faith, or family agreement. Use the complete data option whenever an actual procedure is unavailable or unsuitable.

The key idea

Science answers one narrow kind of question: the kind where you can collect evidence that would change your mind. The question is not whether an idea sounds sensible but whether there is a measurement that could show it is wrong.

Worked examples

Example 1 · Two explanations for a puddle

Explain what the measurements show and why sunlight alone is not established as the cause.

Identify mass lost and the stated hour.
Name both changed conditions.
Propose a matched comparison and a limited claim.

Answer: The sunny tray lost 4 g more in the hour, but sunlight and surface area both differ. Greater exposed area could also affect evaporation. Use identical trays with equal water amounts and matched timing, varying only the intended exposure. The present evidence describes a difference without isolating its cause.

Example 2 · Transfer to a different case

A photograph shows a wet pavement. Does it establish that rain caused the water?

Identify the distinction and conditions in this new case.
Use the relevant mechanism or quantity; preserve units and the chosen boundary.
Explain why the answer fits and what further evidence would be needed.

Answer: No. It shows water at that moment; washing, irrigation, or another source could be involved. A cause needs additional information.

Example 3 · Ask a question that evidence can address · a focused example

Why is the first towel question clearer?

State the literal condition or observation in the example.
Apply the distinction explained in this teaching part.
Check whether the claim stays within the given evidence.

Answer: It defines the measured outcome, time, and piece size. The result concerns that absorption test, not every possible meaning of best.

Avoid these mistakes

Misleading claim: A plausible explanation is automatically a directly observed fact.
Misleading claim: Every scientific investigation must follow exactly the same steps.
Omitting units, measurement timing, or a model boundary makes the evidence hard to interpret.
Treating illustrative classroom data as real field measurements or copying a model is not an independent explanation.

Check your understanding

Does a yellow leaf prove lack of water?

Discuss the answer

No. The color is an observation; the proposed cause needs additional evidence that distinguishes it from other explanations.

Why is the first towel question clearer?

Discuss the answer

It defines the measured outcome, time, and piece size. The result concerns that absorption test, not every possible meaning of best.

What reasoning connects mass gain with absorption?

Discuss the answer

Water retained in the towel adds mass. Comparable dry-to-wet measurements can therefore compare retained water, while spills and timing must be checked.

Can one absorption result rank every towel property?

Discuss the answer

No. The result concerns one measured property under a stated method; cost, durability, and waste need their own evidence.

Sustained scientific explanation and revision

These activities are scheduled in the parent plan. Save a first response, a correction, and the reason for the change in the science notebook.

Activity 1 · Scientific Inquiry: Questions, Evidence & Explanations · Model and explain

Assigned reading and preparation

Read A Neat Result Is Not Yet an Explanation and the linked unit teaching; use its complete supplied case and diagrams.

Your task

For Scientific Inquiry: Questions, Evidence & Explanations, study Parts 3–4 and attempt the worked case: Explain what the measurements show and why sunlight alone is not established as the cause. Explain the steps before opening the model.

Success criteria

An accurate scientific claim answering the actual question.
Relevant evidence or a labeled model with quantities and units when applicable.
Reasoning that connects evidence with the mechanism rather than only repeats it.
A specific method, boundary, scale, or alternative-explanation limit.

Hint

Begin with the actual observation, quantity, or diagram relationship. Explain how it bears on the question before making a broad claim.

Response guidance — discuss after your attempt

The sunny tray lost 4 g more in the hour, but sunlight and surface area both differ. Greater exposed area could also affect evaporation. Use identical trays with equal water amounts and matched timing, varying only the intended exposure. The present evidence describes a difference without isolating its cause.

Activity 2 · Scientific Inquiry: Questions, Evidence & Explanations · Practice, revise and exit

Assigned reading and preparation

Read A Neat Result Is Not Yet an Explanation and the linked unit teaching; use its complete supplied case and diagrams.

Your task

For Scientific Inquiry: Questions, Evidence & Explanations, complete practice questions 1–6 and both choice checks, then answer independently: A photograph shows a wet pavement. Does it establish that rain caused the water? Save a correction explaining one changed claim or method.

Success criteria

An accurate scientific claim answering the actual question.
Relevant evidence or a labeled model with quantities and units when applicable.
Reasoning that connects evidence with the mechanism rather than only repeats it.
A specific method, boundary, scale, or alternative-explanation limit.

Hint

Begin with the actual observation, quantity, or diagram relationship. Explain how it bears on the question before making a broad claim.

Response guidance — discuss after your attempt

No. It shows water at that moment; washing, irrigation, or another source could be involved. A cause needs additional information.

Words to know

observation: A recorded detection or measurement under a stated method.
inference: A reasoned interpretation of observations rather than the observation itself.
evidence: A relevant observation, measurement, or record used to evaluate a claim.
system boundary: The chosen limit specifying what is included and which exchanges cross it.
uncertainty: A stated limit in measurement or knowledge, distinct from a careless mistake.

In the real world

A doctor uses the exact same loop you do: she observes your symptoms, forms a hypothesis (a possible diagnosis), tests it with a lab test or scan, analyzes the results, and concludes what is wrong — then adjusts if the evidence points somewhere new.

Exit check

A photograph shows a wet pavement. Does it establish that rain caused the water?

Check your explanation after answering

No. It shows water at that moment; washing, irrigation, or another source could be involved. A cause needs additional information.

Explain your reasoning without notes. If a key idea is missing, revisit the lesson and try again.

Problem 1

Does a yellow leaf prove lack of water?

Answer and explanation

No. The color is an observation; the proposed cause needs additional evidence that distinguishes it from other explanations.