Knobs and notebook

The idea

To investigate a scientific question, first list the things that can be changed or controlled, and then the things that can be observed or measured, either as yes/no answers or as numbers.

Two lists

To find out what changes the way a puri puffs, a scientist makes two lists before frying anything.

Which list do you think comes first?

• Things I can change or control
• Things I can observe or measure
• Both lists at the same time

Fill the planning page

A note card shows one thing from the puri investigation. Tap the part of the page it belongs in.

Change, then observe

First list what we can change or control. Then list what we can observe or measure: either a yes or no answer, or a number.

The first column holds the knobs we turn. The second holds the notebook entries that tell us whether turning a knob made any difference.

• We can change or control | We observe or measure
• Thickness and size of the dough | Does the puri puff? (yes or no)
• Kind of flour | Does a very thick dough still give a thin side? (yes or no)
• Oil temperature, and how the dough is dropped | Time to puff (a number, in seconds)

Notes

First list what can be changed or controlled, then what can be observed or measured: yes or no answers, or numbers.

Check yourself

A student tests whether the amount of sunlight changes how fast a bean seedling grows. Which of these can she change or control?

In the same experiment, which one is a yes or no observation?

Here are six items: oil temperature, *does the puri puff?*, thickness of the dough, *time to puff*, kind of flour, *does a thick dough still give a thin side?* How many of them do we observe or measure?

Answer: 3

Observed or measured: does it puff (yes or no), time to puff (number), thin side (yes or no). The other three are things we change or control.

• The height of the seedling after a week. She measures this. It is an observation, not a knob she turns.
• Whether the seed sprouted. She observes this (yes or no). She cannot choose it.
• The amount of sunlight the pot gets — correct. Yes. She can place the pot in more or less sunlight, so it is something to change.
• The number of leaves she counts. She counts these. It is a number she observes.
• Height of the seedling in cm. Height is a number, not a yes or no.
• Did the seed sprout? — correct. Yes. The answer is yes or no.
• Hours of sunlight given. That is something she changes. It is a number, but not an observation.
• Number of leaves. That is a number, not a yes or no.