Scientific Tutor

What sections should I know before attempting to learn this section?

—> Introduction to Units

 

What are unit prefixes?

In addition to the basic chemistry units, you also have the prefixes that modify the original unit. They are laid out in this table I have created below that I call the unit prefixes table.  Keep this table open as you are learning and practicing through the rest of the chapter.

That looks like a lot of units to memorize but what I want you to focus on the 3 most important ones. Those are milli (m), centi (c), and kilo (k).  Look at their last column of information the one called “common ratio”.

 

Milli means 1,000 times smaller. To put it another way, 1000 millimeters = 1 meter.

You can also write that as a proportion or ratio like I do below:

 

1000 mm

1 m

 

or

 

1 m

1000 mm

 

No matter how you write out the statement, it means that 1000 millimeters and 1 meter are the same length measurement. The great thing about this is that when you use metric measurements for conversions, you can write out equations in any order you want to as long as they are true statements.

 

Centi means 100 times smaller. To put it another way, 100 centimeters = 1 meter.

You can also write that as a proportion or ratio like I do below:

 

100 cm

1 m

 

or

 

1 m

100 cm

 

Kilo means 1000 times bigger. To put in another way, 1 kilometer = 1000 meters.

You can also write that as a proportion or ratio like I do below:

 

1000 m

1 km

 

or

 

1 km

1000 m

 

To make future questions on homework, a quiz, or a test, memorize these three prefixes above and how to write them as proportions or ratios.

 

Examples: Write down the ratios in a sentence. Use the unit prefixes table if necessary.

 

How many centimeters in 1 meter?

Answer: There are 100 centimeters in 1 meter.

 

How many kiloliters are in 1 liter?

Answer: 1 / 1000 = 0.001……There are 0.001 kiloliters in 1 liter.

 

PRACTICE PROBLEMS: Write down the ratios in a sentence. Use the unit prefixes table if necessary.

 

How many milliseconds in 1 second?

Answer: There are 1000 milliseconds in 1 second.

 

How many centigrams in 1 gram?

Answer: There are 100 centigrams in 1 gram.

 

How many moles in 1 kilomole?

Answer: There are 1000 moles in 1 kilomole.

 

How many meters in 1 centimeter?

Answer: 1 / 100 = 0.01……There are 0.01 meters in 1 centimeter.

 

How many kilograms in 1 gram?

Answer: 1 / 1000 = 0.001……There are 0.001 kilograms in 1 gram.