WHY DO WE NEED UNITS It's a question as old as time itself. What is the purpose of all of these different units? Some may assert, "I live in America why do I have to learn the metric system?" The fact of the matter is both customary and metric system units, the two systems that we will talk about in depth in this section, will be extremely important aspects of your being for the rest of your life, so why not just learn it now? It is also important to understand inter conversions within these units. Practice questions will be included (with solutions annotated) that strive to help your ability to make these connections. It would also be useless to know these units of measurement without making real world connections. What use would it be to say something was six feet long if nobody had any indication of what six feet actually looked like in the real world. For that reason diagrams and pictures are helpful representations to gain a grasp of what these measurements really consist of in the real world. THE METRIC SYSTEM Now that we have a mutual understanding of why these different units of measurement are important, let us begin to look at the granddaddy of all measurement systems, the metric system. The metric system is a standardized set of measurements that assigns basic values to certain quantities. In the metric system basic quantities are measured as such.Figure 1.1
As we can see in Figure 1.1 different quantities have different designations. These particular set of units are called SI units and represent the most current and accurate depiction of unit measurements in every day life. These seven specific units are called base units because they are independent dimensions that are the basis of deducing other units of measurement. Now that we have the standard basic units we can begin to derive other units from there. For example, volume (length)3, so if the units for length are meters the units for volume would simply be m3. However, in chemistry volume is often measured in liters. So how do these two relate two each other? Well this is the perfect opportunity to look at a problem and try what is called basic dimensional analysis. Don't worry if you struggle with this problem at first, considering we haven't gone over converting within measurements and into different measurements, this problem may seem difficult at first. Nevertheless, in time this will all become second nature to you (we hope).
Problem #1
How many Liters are in one cubic meter?
So now that we understand the basic units let us move on to every chemistry student's favorite subject gulp unit conversion!! Unit conversions within the metric system are based on prefixes which have been highlighted in Figure 1.2 below.Figure 1.2
Most general chemistry professors require students to understand the table from kilometer to picometer, although there is obviously a lot of variation. When I was younger they made me memorize mnemonics to remember the prefixes. However, whatever works best for you in order to memorize these prefixes should be used, because these prefixes are very important in the overall understanding of metric conversions. Now that we understand these prefixes we can convert between prefixes within the same units. For example, we can convert 50 km into 50,000 m with limited strain. This brings us to Problem 2.
Problem #2
If there are 2.54 centimeters in an inch, how many inches are in 50 meters? Round to 2 decimal places.
As we can see in Figure 1.1 different quantities have different designations. These particular set of units are called SI units and represent the most current and accurate depiction of unit measurements in every day life. These seven specific units are called base units because they are independent dimensions that are the basis of deducing other units of measurement. Now that we have the standard basic units we can begin to derive other units from there. For example, volume (length)3, so if the units for length are meters the units for volume would simply be m3. However, in chemistry volume is often measured in liters. So how do these two relate two each other? Well this is the perfect opportunity to look at a problem and try what is called basic dimensional analysis. Don't worry if you struggle with this problem at first, considering we haven't gone over converting within measurements and into different measurements, this problem may seem difficult at first. Nevertheless, in time this will all become second nature to you (we hope).
Problem #1
How many Liters are in one cubic meter?
So now that we understand the basic units let us move on to every chemistry student's favorite subject gulp unit conversion!! Unit conversions within the metric system are based on prefixes which have been highlighted in Figure 1.2 below.Figure 1.2
Most general chemistry professors require students to understand the table from kilometer to picometer, although there is obviously a lot of variation. When I was younger they made me memorize mnemonics to remember the prefixes. However, whatever works best for you in order to memorize these prefixes should be used, because these prefixes are very important in the overall understanding of metric conversions. Now that we understand these prefixes we can convert between prefixes within the same units. For example, we can convert 50 km into 50,000 m with limited strain. This brings us to Problem 2.
Problem #2
If there are 2.54 centimeters in an inch, how many inches are in 50 meters? Round to 2 decimal places.
( Chemistry Genius )
www.ChordsAZ.com