Significant Figures

Significant Figures

Significant Figures

There are 2 different types of numbers

1. Exact numbers 2. Measured numbers - they are measured with a

measuring device so these #s have ERROR.

When you use your calculator your ans. can only be as accurate as your worst measurement

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Exact Numbers

An exact # is obtained when you count objects or use a defined relationship.

Counting objects are always exact 2 soccer balls 4 pizzas

Exact relationships, conversions, are not measured 1 foot = 12 inches 1 meter = 100 cm 1 mole = 6.02 x 1023 particles

For instance, is 1 foot = 12.000000000001 inches? No 1 ft is EXACTLY 12 inches.

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Pencils down. Learning Check #1

More than one answer may be correct!

A. Exact numbers are obtained by 1. using a measuring tool 2. counting 3. definition

B. Measured numbers are obtained by 1. using a measuring tool 2. counting 3. definition

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Pencils down.

Solution

A. Exact numbers are obtained by 2. counting 3. definition

B. Measured numbers are obtained by 1. using a measuring tool

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