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Chemistry: SI Units & ConversionsPowerPoint Presentation

Chemistry: SI Units & Conversions

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Chemistry: SI Units & Conversions

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Chemistry: SI Units & Conversions

- Time: second (s)
- Length,distance: meter (m)
- Mass: kilogram (kg)
- In class, we consider the “base unit” to be grams.

- Volume: liter (l)
- Temperature: Kelvins (K) note: no degree symbol
- In chemistry lab, we use the Celsius temperature scale. ( °C)

- A derived unit is one in which the units are combined mathematically.
- Volume: cubic centimeter (cm3)
- (cm x cm x cm)

- Area: square meter (m2)
- ( m x m)

- Density: mass volume

- Volume: cubic centimeter (cm3)

Kelvins = C + 273

°C = Kelvins - 273

- Prefixes for units smaller than 1:
- micro () 1 X 10-6 or
- milli (m) 1 X 10-3 or
- centi (c) 1 X 10-2 or
- deci (d) 1 X 10-1 or

- Prefixes for units larger than 1:
- kilo (k) 1 X 103 or 1,000

Conversion Using the Factor-Labeling Method : (Dimensional Analysis)

Starting unit

Target unit

Problem: Convert 32.05 cm to m

=

X

Step 1: write down the starting measurement: number and unit!

Step 2: Convert from this prefix to the base unit. (This means meters, liters or grams.)

Step 5 If you have arrived at the target unit, you are done!

Be sure to include the unit and significant figures in your answer!

Step 3: Cancel the units that divide each other out.

Step 4: Perform the math… divide by the numbers on the bottom, multiply by the numbers on the top!

Practice!

Convert 0.00450 km to cm

?

X

X

=

The correct answer is 450 cm, but that’s only 2 sig figs…. ?????

Use scientific notation to correct the sig figs!

4.50 x 102 cm