How to plan an investigation

Making an idea into a question

Amna wants to test her idea. She makes it into a question 'Does stirring make sugar dissolve more quickly?'.

Choosing the equipment

They decide to dissolve the sugar in hot water and use clear containers. They put the containers onto black card. This will help them to see the sugar.
Neta gets a stopwatch so that they can measure how long the sugar takes to dissolve.

Making the test fair

What do they need to keep the same to make the test fair?
They make a list of the variables.

Variables: Amount of sugar - Amount of water - Temperature of water - Amount of stirring

Making the test accurate

It is not important who stirs the sugar in this investigation.

Choosing equipment

It is important to choose the right science equipment for an investigation.
Using the right equipment can make measurements more accurate.
Sunil wants to measure how much water he has. He can see it is between 70 and 80 ml but he wants an accurate measurement.

Sunil knows that he needs to use a measuring cylinder but he is not sure which one. Look at the water in the measuring beaker. Which measuring cylinder will give the most accurate measurement?
The 50 ml measuring cylinder is too small.

Sunil tries the others.
For an accurate measurement, use the smallest measuring cylinder that the liquid will fit into.
Use this page to help you choose what you need for your investigation.

Using forcemeters scales

Using a forcemeter

Turn the nut to check the forcemeter is set to zero.
Put the object on the forcemeter.
Put your eye level with the pointer and read the scale.
The weight of the bananas is a force of four newtons.
Many forcemeters also have a scale that will show the mass of an object in grams or kilograms.
The bananas have a mass of about 400g.
Some forcemeters can also be used to measure the size of a pushing force.
A force of about 2.5 N is needed to push this book across the table.

Using scales

These scales are not set to zero.
Look for a wheel at the back of the scales. Turn the wheel to set the scales to zero.

Put an object on the scales.
The scales will show the mass of the object.
This apple has a mass of 250g.

Looking for patterns in results and making conclusions

 There are often patterns in results. The pattern might be results that are all the same, or it might be measurements that go up or down.
Femi and Kwasi are investigating which materials conduct electricity.
They are testing objects made from different materials. The bulb lights when the material conducts electricity. Here are their results.

Bulb	Material	Object
on	metal	scissors
off	wood	ruler
off	plastic	cup
off	glass	cup
on	metal	key
on	metal	coin
off	paper	book
on	metal	spoon
off	wood	spoon
on	graphite	pencil lead
off	plastic	pen

Femi has seen a pattern in the results. Some of the results are the same. He uses the pattern to make a conclusion. Is Femi correct?
Kwasi has seen a result that does not fit the pattern.

To check that they have not made a mistake, they repeat the test with the graphite. The bulb lights up every time. So Femi's conclusion is not right.
They make new conclusions.

Using patterns to check that repeated measurements are reliable

Yoko and Marja are investigating how running affects pulse rate. They want to know if their pulse rate is different when they run at different speeds.
Yoko runs the same distance each time but at three different speeds.
To make their results reliable, Yoko runs at each speed three times. They measure her pulse rate after each time. They are going to take the average pulse rate for each running speed by finding the mean.

Here are their results so far.

Running slowly	Running very fast	Running quite fast	Exercise
155	102	190	Pulse Rate 1 in beats per minute
153	172	195	Pulse Rate 2 in beats per minute
210	178	188	Pulse Rate 3 in beats per minute
			Mean pulse rate in beats per minute

The girls look for patterns in their results. The numbers for running very fast are almost the same. But there are two measurements in the results that could be wrong. Look for numbers that do not fit the pattern.
The girls repeat two measurements to check that they are reliable. Then they calculate the mean.
 Their results now look like this.

Running slowly	Running very fast	Running quite fast	Exercise
155	169 - 102	190	Pulse Rate 1 in beats per minute
153	172	195	Pulse Rate 2 in beats per minute
148 - 210	178	188	Pulse Rate 3 in beats per minute
152	173	191	Mean pulse rate in beats per minute

Marja makes a conclusion.

The girls explain why they repeated their measurements.

Researching questions

Sometimes a science investigation is not the best way to answer a question. You may not have the equipment you need or enough time. The answers to many questions can be found in reference books or on the internet. Mai is researching food chains.

Choosing key words

First you should think about which words to look for. These should be key words for the topic you are researching. Mai could look for diet, consumer and prey.

Using reference books

Scan the contents page for these words and look them up in the index.
Try looking up consumer and prey in the index to this book. Can you find out about the diet of an animal?

Using the internet

Think carefully about the words you type into a search engine. Searches for 'Crocodile dieť and What do crocs eat?' will list different websites.
Not all the information the internet is correct, so look carefully at the websites that come up on your search. Some are more likely to be correct than others.
Mai has found two websites with information about what crocodiles eat. Which do you think is more reliable?
To find reliable websites, look for those that come from large organisations and are written by experts. Unreliable websites often have adverts and do not look as good.