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Scientists use observation and inference to answer questions In this topic, you will learn that:
• good scientists need to be observant and notice things around them • quantitative observations usually contain numbers with units • qualitative observations contain words and descriptions • scientists use observations to infer (explain) what is happening.
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The skill of observation usually requires you to notice small differences. Figure 1 shows two scenes. There are 10 differences between the two. Can you find them all?
qualitative observation an observation that uses words and is not based on measurements or other data
Figure 1 Use your observation skills to identify the differences between the two pictures.
Quantitative or qualitative observations quantitative observation an observation that uses a number, such as a measurement
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Quantitative observations use measurement – they are ‘amounts’ or quantities and are normally written using numbers. The numbers are usually accompanied by units that describe the size or what is being measured, such as 2.7 m or 23.4 degrees Celsius (°C). For example, 10 m is a measurement of length, while 10 L is a measurement of volume.
Figure 2 A qualitative observation would be that this substance was dark yellow.
Qualitative observations use words to describe anything that is not an amount. The five main sense organs of the human body are essential for qualitative observations. What you see, hear, smell, taste or feel are generally qualitative observations. ‘Rough’, ‘sour’ and ‘yellow’ are all words describing qualitative observations.
Testing your senses The secret to being observant is to use your senses. The activities in this unit will make you more aware of your senses. In some activities you will need a blindfold. It is best to use safety glasses that have been painted black or covered with dark paper. You will not test your fifth sense, taste, because it is not good safety practice to eat in a laboratory.
OXFORD UNIVERSITY PRESS OXFORD SCIENCE 7: VICTORIAN CURRICULUM No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means.
