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Scientific method – chemistry

Scientific method – chemistry

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What does pH measure?

Scientific method – chemistry

Everyone knows: pineapple juice is much nicer than orange juice. In your opinion, yes. - I think the OPPOSITE. - And, as always, - you're WRONG. -YOU are wrong! No, I'm right! Orange juice IS nicer! NO!

Stop fighting now! Because... you can't measure which juice is NICER. You can't measure something that's just an OPINION. But I don't like sour juices… and orange juice is ALWAYS more sour than pineapple.

In a scientific investigation you begin just as Jenny did now - from a guess or an assumption. This is called forming an hypothesis. In order to determine whether the hypothesis is true or false - you carry out experiments. Sourness can be measured scientifically. The unit we measure with is called pH.

The more sour or acidic a substance is, the lower its pH. You can measure pH with an electronic device that you put in the juice. ... let's see, the pH of the pineapple juice is 4.0. ... and for the orange juice it's 3.5. There, you see, Michael!

Orange juice is more acidic! But what if it's only THIS orange juice that's more acidic? There are many different kinds of orange juice. Michael is right. We have to make more measurements to see if Jenny's hypothesis holds.

Jenny has found ten different kinds of orange juice, and as many different kinds of pineapple juice in the store. Pineapple 3.4... - orange 3.7. - Yes! But then pineapple IS more acidic! Well, when Jenny and Michael write down the results, they see that there is quite a big variation among the juices. I don't get how we should interpret this!

Which one is more acidic? In a scientific experiment, it's not enough JUST to investigate. You also need to analyze the results of the investigation. The first test showed that this particular pineapple juice was more acidic than that orange juice. This means we can dismiss Jenny's hypothesis that orange juice is ALWAYS more acidic - than pineapple juice.

What I meant is that orange juice is more acidic - GENERALLY SPEAKING... like... What, are you changing the HYPOTHESIS NOW? When a hypothesis has been proven wrong in a scientific investigation, you can form a new hypothesis: Is orange juice on average more acidic than the juice from pineapples? This is what we do to test our new hypothesis: The value of each pH measurement is added together and divided by the number of measurements - in this case, ten.

The analysis of the investigation clearly shows that the orange juices that Jenny and Michael bought are, are, on average, more acidic than the pineapple juices... And thus that confirms the new hypothesis! The method Jenny and Michael used to arrive at a conclusion is called the scientific method. This is how we can describe the different steps in the scientific method: Identify a problem - What is it I want to find out? Formulate a hypothesis - How do I think things are connected?

Carry out an investigation or an experiment - to test whether the hypothesis is correct. Carefully gather the data - in a controlled way. Analyze the data - in order to draw a conclusion. Does the conclusion fit the hypothesis? If it does, then the hypothesis is true - or verified.

That means that you have gained new knowledge. But if the hypothesis must be dismissed, it can mean that the investigations were not good enough, or that the hypothesis was wrong. Then you either need to redo the investigations, or come up with a new hypothesis. Although actually, I like apple juice best. No, cranberry juice is nicer!

You cannot be serious!