MEASUREMENT IN CHEMISTRY SI (Metric System) Units

Prefixes

Factor Label Method

Equipment

Using density for identification and applications

2. Measurement in Chemistry• Measurements in chemistry always require a

________________ & a ________________.

• NO ___________________ numbers!

• We use the International System (SI), which is similar to the metric system:

SI Units

Quantity Common unit Measurement Equipment

Mass

Length

Time

Temperature

SI Temperature: Celsius or Kelvin

SI Units

Quantity Common Unit Measurement Equipment

Amount of Substance

Energy

Volume of a Liquid

Volume of aSolid

Small and large units • Everyday units (English System)

• Length Paperclip:

Laptop

Whiteboard

Sandy Porter Road

• Metric System: Similar system but using prefixes

Small and large measurements

SI System: Based on Powers of Tenhttp://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

http://www.unc.edu/~rowlett/units/prefixes.html

Important SI Prefixes

Kilo-k

Hectoh

Deka-da

Base Decid

Centi-c

Milli-m

1000 100 10 1 0.1 0.01 0.001

10³ 10² 10¹ 10° 10⁻¹ 10⁻² 10⁻³

1 meter

1 Liter

1 gram

Equivalent amounts - Memorize! • 1 kilometer (_____) = _______ meters • 1 hectometer ( ) = ________ meters • 1 dekameters ( ) = ________ meters

• 1 meter = ________ decimeters• 1 meter = ________ centimeters• 1 meter = ________ millimeter

Memory tool: King Henry Died by Drinking Chocolate Milk

Measurements in chemistry calculations must have the same ____and ______.

To covert: • Given Quantity x Conversion Factor = Unknown (or desired) Quantity • A known beginning=• A desired end=• A connecting path=

Factor Label Method

•Please note: There are other ways to do the metric conversions. However, the following method will be used in chemistry to help prepare for the more difficultmole calculations, which will be in the next unit.Use the other methods to check your answers.

Factor Label Method

The most important mathematical process in chemistry!

• A known beginning = GIVEN• A desired end= UNKNOWN• A connecting path = CONVERSION FACTOR

Conversion Factor

• Uses equal quantities• 60 seconds = 1 minute• 1 km = 1000 meters

• Conversion factors can be written as ratios• Ratios are written as “tops or bottoms” depending on the units to be cancelled.

Example: How many centimeters are in 6.4 meters?

Example Problems: Given quantity & unit x Unknown unit = Unknown quantity & unit Given unit

1. How many grams are in 463 kilograms? • Given: • Unknown: • Conversion factor: Solve:

Example Problems: Given quantity & unit x Unknown unit = Unknown quantity & unit Given unit

2. How many milliliters are in 2.5 liters? • Given: • Unknown: • Conversion factor: Solve:

Example Problems: Given quantity & unit x Unknown unit = Unknown quantity & unit Given unit

3. How many meter(s) are equal to 16 centimeters?• Given: • Unknown: • Conversion factor: Solve:

Factor Label - Multiple steps example

• Calculate the number of seconds in one day.• 60 seconds = 1 minute• 60 minutes = 1 hour• 24 hours = 1 day

Given Desired = sec

1 day 24 hr. 60 min. 60 sec =

1 day 1 hr. 1 min.

If you are changing prefixes for a measurement:

S ↔ B

Size of the number

(quantity)

Smaller Prefix for the Unit

LargerPrefix for the Unit

Small Big

Unit Prefix

Double check your answers!

SI Prefixes