Chemistry · Class 9-10 · Chapter 1 · The idea of chemistry
How a question gets answered.
This is the most useful part of the chapter and the least remembered, because it is not a fact but a method. Once you have it, it works outside chemistry too, since the steps really belong to any question at all.
1. What research actually means
The definition is as plain as it is important: research is trying to find something out by testing it. And one thing follows from that directly, which the book is not shy about saying: whoever follows the process is a scientist. It does not take a large laboratory or expensive equipment. It takes the rule.
The widget below runs one small experiment from beginning to end. The question is this: when ammonium chloride (NH₄Cl) dissolves in water, is heat given out or taken in? Walk the steps, and watch how the drawing above them changes.
step by stepwalk the steps
One question, start to finish
Set the question. It has to be a question a test can answer. “Is chemistry beautiful” cannot be measured; this one can: when NH₄Cl dissolves in water, is heat given out or taken in?
Gather what is known. Look in books and at earlier work. You find that some substances give out heat as they dissolve, lime for one, and others take heat in. So it cannot be assumed either way. Skip this step and you spend your time discovering what was already known.
Plan the work. Decide what you need: a beaker, a measured volume of water, a thermometer, a stand, a spoon and a weighed quantity of NH₄Cl. Decide what you will measure too, before you start: the temperature after each addition.
Make a hypothesis. From what you know, set up a likely answer in advance. It is a claim the experiment could prove wrong, and that is its whole job. A hypothesis is not something you defend. It is something you try to break.
Run it and record. Write down the temperature of the water first. Then add the NH₄Cl a little at a time, stirring and reading the thermometer after each addition. Write what happens, not what you were expecting.
Test the hypothesis. Look at the list. The temperature fell after every addition, and the beaker feels cold. So dissolving is taking heat in from its surroundings. If the hypothesis had said the opposite, then the hypothesis would have to change, not the readings.
Settle it. Not on one run. Do the experiment several times, and only if it comes out the same every time do you conclude: dissolving NH₄Cl in water takes heat in, which makes it an endothermic process.
Publish it. Write down what you asked, how you tested it, what you found and what you concluded, and put it where others can repeat it and check. Without publishing, the work does not become science, and this is exactly where the alchemists used to stop.
The drawings are models, not scale drawings.
The steps are not for reciting, they are for running. And the two places people get the order wrong are these: gathering what is known comes before the experiment, and publishing comes last. Read nothing first and you rediscover the known; publish nothing at the end and nobody can check you.
check yourselfpick one answer
Which one comes last
What is the last step of the research process?
The experiment sits in the middle. After it come testing the hypothesis, repeating the work, and publishing.
The hypothesis comes early, before the experiment. What comes after the experiment is not a hypothesis, it is a conclusion.
Right. The work ends by being published, so that other people can repeat the experiment and check it. Unpublished, the claim cannot be tested, and a claim that cannot be tested is not science.
Gathering information is an early step, before the experiment. Putting it last turns the whole order upside down.
2. Why it has to be measured
The step that gets skipped most easily is the measuring, because the answer often feels known in advance. Put a second substance beside the first and that feeling collapses. Add lime to water and the vessel gets hot, so heat is coming out. Add NH₄Cl and it gets cold, so heat is going in. Both are dissolving, and they go opposite ways.
Which is why nothing can be assumed. Tap either one and see which way the temperature goes.
by handtap either substance
You only know once you measure
The graph is a model of the direction only. There are no measured readings in it; if you run the experiment, the numbers will be your own.
Taking heat in makes a process endothermic; giving heat out makes it exothermic. Concentrated sulphuric acid (H₂SO₄) in water also releases a great deal of heat, enough that it becomes a question of safety as well. The chapter comes back to that at the end.
which firsttap whichever comes first
Put the steps in order
Which one is first? The one without which nothing else can start.
Yes. And the next?
Not yet. There is a step before this one.
That is it. The two places people slip are these: gathering information comes before the experiment, and publishing comes last of all.
3. A hypothesis and a conclusion are not the same thing
Confusing these two is the costliest mistake here. A hypothesis comes before the experiment, and it is a claim that could turn out wrong. A conclusion comes after, and not after one run either, but after the same result has come back several times.
And the rule standing between them is the backbone of the whole enterprise: when the data and the hypothesis disagree, the hypothesis is what changes, not the data. You can save a hypothesis by editing the readings, and then there is nothing left that anybody knows.
Below are eight sentences lifted out of a student's notebook. Tap each one and see which step it belongs to.
from the notebooktap any sentence
Which step is this sentence from
Setting the question. Choosing a question a test can answer. Notice that this one has two possible answers and both of them can be checked by measuring.
Gathering what is known. Looking up what other people already know. This sentence belongs before the experiment, not after it.
Planning the work. Deciding the materials and the method in advance. What will be measured is decided here too.
The hypothesis. Nothing has been proved yet. The words “I think” are the giveaway that this is not a conclusion, and the experiment exists to break it.
Running it and recording. Writing down what happened. There is no interpretation in this sentence, only a reading.
Testing the hypothesis. Holding the hypothesis up against the data. It matched, which is fine; had it not, that would have been fine too, and the hypothesis would have changed.
Settling it. One run is not enough. The words “three times” are what separate this step from the one before it.
Publishing. It is science because somebody else can check it. Handing in the notebook is publishing on a small scale, and the principle is the same.
All eight. The hard pair was “I think” and “did it three times”, which is to say the hypothesis and the conclusion. One comes before an experiment, the other after several.
check yourselfpick one answer
The beaker feels cold
When ammonium chloride dissolves in water the beaker feels cold. What follows from that?
If heat were being produced the beaker would feel warm, as it does with lime or concentrated H₂SO₄. Feeling cold points the other way.
Right. Cold to the touch means heat is leaving the beaker and its surroundings, which is to say the dissolving is absorbing it. That is an endothermic process.
Evaporation does take heat, but what is happening here is dissolving, and the temperature drops the moment the solid goes in. Water at room temperature does not evaporate that fast.
If nothing were dissolving there would be no change in temperature at all. The change is itself the evidence that something is going on.
4. The steps are not chemistry's
Here is the last thing: none of this is special to chemistry. “Why are my plant's leaves going yellow” runs on exactly the same steps. First find out what makes leaves go yellow. Then set up a guess, say that it is being watered too much. Then water two plants differently and write down what happens. Then compare, and then do it again a few times.
And do not drop the last step, even for the plant. Tell somebody who can tell you back. If you say it out loud, someone may catch your mistake, and catching mistakes is what the whole method is for.
check yourselfpick one answer
When the guess does not hold
A student guessed that adding NH₄Cl would raise the temperature, and the experiment shows it falling. What should they do now?
Editing the data saves the guess and kills the knowledge. This is the one move that makes everything else on the page worthless.
A hypothesis being disproved is not a failure, it is a result. This run taught the most of any of them, because it removed a wrong belief.
Right. This is the central rule: when the data disagrees with the hypothesis, the hypothesis changes, not the data. Then the experiment is repeated until it is certain.
An instrument really can be faulty, but that is something to check, not to assume. Measuring again with a second thermometer is a fair move; assuming is not.