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# Units, Measurement and Conversions

Units, measurement, and conversions are among the first topics covered in any science class, including chemistry. Learn about the basic units of measurement and how to convert between them.

Metric Unit Prefixes
Metric units of measurement are all based on units of ten. Here is a list of the most common metric unit prefixes.

Metric Units - Base Units
The metric system or SI (from Le Système International d'Unités.) is based on seven base units. These units describe the basic properties on which all other measurements are based.

Metric Units - Derived Metric Units
Many metric units used in science have specialized names for the values they represent. They are considered derived units and can still be reduced to factors of the seven base units. This table lists many of these units and their corresponding base unit values.

Pressure Conversions
Here are some examples of conversions between units of pressure (kPa, atm, mm Hg).

Temperature Conversions
These are examples of temperature conversion problems, with links to other worked chemistry problems and homework help.

Unit Conversions
These are examples of unit conversion problems, with links to other worked chemistry problems and homework help.

Area, Perimeter & Volume Formulas
Perimeter, surface area and volume formulas are used for many chemistry calculations. You may need to find surface area and volume to determine density and concentration, for example. While it's a good idea to memorize these formulas, here a list of formulas to use as a handy reference.

Celsius to Kelvin Temperature Conversion
Here is an example problem that explains how to convert a temperature from degrees on the Celsius scale to Kelvin.

Constants, Prefixes, Conversion Factors
This is a set of tables with some useful physical constants, conversion factors, and unit prefixes. They are used in many calculations in chemistry, as well as in physics and other sciences.

Concentration and Molarity
These are examples of concentration and molarity calculations, with links to other worked chemistry problems and homework help.

How Do I Read a Meniscus?
The meniscus is the curve seen at the top of a liquid in response to its container. When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask, it's important that the measurement accounts for the meniscus. Here's how to read a meniscus.

Mean or Average - Calculate the Mean
It's very important to know how to calculate the mean or average of a set of numbers. Among other things, this will allow you to calculate your grade point average. However, you'll need to calculate the mean for several other situations, too.

Measurements & Conversions Quiz
Take a multiple choice quiz to test your comprehension of units, conversions, and significant figures.

Metric Prefixes Quiz
How well do you know your metric prefixes? Quiz yourself with this ten question multiple choice self-test.

English to Metric Conversions - Unit Cancelling Method
Here is a worked example of how to convert English to Metric measurement units using the unit cancellation method. This example converts yards to meters.

Metric to Metric Conversions - Unit Cancelling Method
Here is a step by step example of a conversion between metric units. This illustrates how to cancel units to convert measurement units.

Molality Example Problem
Here is an example of calculating concentration or molality of a solution.

Molarity Example Problem
Here is an example of calculating concentration or molarity of a solution.

Mole - Gram Conversions
These are examples of mole-to-gram and gram-to-mole conversions, with links to other worked chemistry problems and homework help.

Scientific Notation
Scientific notation uses exponents to express numerical figures. Here's an explanation of what scientific notation is, plus examples of how to write numbers and perform addition, subtraction, multiplication and division problems using scientific notation.

Significant Figures in Measurements and Calculations
This article discusses the use of significant figures in taking measurements and performing calculations. Learn about significant figures, uncertainty, accuracy, precision, rounding, and truncating. Losing significant figures and effects of exact numbers are also described.

Significant Figures
These are examples of significant figure, accuracy, and precision problems, with links to other worked chemistry problems and homework help.

Surface Area and Volume Formulas
Surface area and volume formulas are part of the math used in common science calculations. You may need to calculate surface area and volume to determine density, pressure and concentration, for example. While it's a good idea to memorize these formulas, here a list of surface area and volume formulas to use as a handy reference.

Table of Physical Constants
Need a value for a fundamental physical constant? This handy reference table contains commonly used physical constants used in chemistry.

Temperature Converter
Here's a handy online converter for temperatures. Simply enter your known temperature (Kelvin, Celsius, Fahrenheit) and the other values will appear. It's much easier than trying to remember the formulas or do the math!

Unit Conversion Worksheets
Use these printable worksheets to practice unit conversions. These pdf questions and answers will test your understanding of metric-metric, metric-English, and temperature conversions.

Units of Measurement Quiz
How well do you know the basic units of measurement? Here's a ten question quiz covering both metric and English units that you can take to test yourself.

What Is a Mole and Why Are Moles Used?
No, we're not talking about the small burrowing mammal! Here's a look at a standard unit in chemistry and why it's used.

What Is Absolute Zero?
Learn about absolute zero and the Kelvin and Celsius temperature scales.

Why Is lb the Symbol for Pounds?
Have you ever wondered why lb is used as the symbol for the pounds unit? Here's the answer to the question.

How to Convert Celsius to Fahrenheit
It is easy to convert Celsius to Fahrenheit with these steps.

How to Convert Fahrenheit to Celsius
It is easy to convert Fahrenheit to Celsius with these steps.

How to Convert Fahrenheit to Kelvin
It is easy to convert Fahrenheit to Kelvin with these steps.

How to Convert Celsius to Kelvin
It is easy to convert Celsius to Kelvin with these steps.

How to Convert Kelvin to Fahrenheit
It is easy to convert Kelvin to Fahrenheit with these steps.

How to Convert Kelvin to Celsius
It is easy to convert Kelvin to Celsius with these steps.

What Is the Difference Between Accuracy and Precision?
This is an explanation of the difference between accuracy and precision.

What Is the Difference Between Quantity and Unit?
Learn the difference between a unit and a quantity and get examples.