Why does the same reaction crawl in one test tube and race in another?
You can think of a reaction as a chemical change where your starting substances turn into new substances. What you actually care about in kinetics is speed: how quickly that change happens.
After you’ve described the change, you give it a name.
<strong>Rate of reaction</strong> means the amount, mass, volume, or concentration of a substance changing over a certain time interval.
The compact way to write that is
Your “quantity” depends on what you measured in the lab. If you tracked concentration, your unit could be mol dm⁻³ s⁻¹. If you followed mass loss, you might use g s⁻¹, and if you collected a gas, cm³ s⁻¹ makes sense.
If your teacher asks for a rate, check what your data table measured first. Your unit must match that measurement divided by time.
A surprising bit is that you do not always measure the reaction directly. You usually watch some visible clue change with time, then use that clue to work out how fast the reaction is going.
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