Ever shed points top top a test since you forgot to compose the units?

Rightfully so! Numbers have actually no meaning without their devices of measurement. Two have the right to be greater than 12. Three have the right to equal one. This is every dependent ~ above the unit of measurement being used. In your general chemistry class, you will certainly encounter measurements of all sorts. This measurements include time, length, mass, volume, and many more. Devices of measure up are offered to conceptualize the size of this measurements. Gram, kilogram, pound, ounce, metric ton, stone, slug, microgram, atomic mass unit, carat… these room all systems of measurement because that mass alone. Why for this reason many? Some systems of measurement are more appropriate depending on what thing is gift measured. Utilizing an inappropriate unit of measure may result in a number value that is too huge or as well small. Once this happens, it i do not care very an overwhelming to wrap her head around the size of the measurement.

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Conversion factors and also their usage

A conversion variable is provided to change the unit of measure up without transforming its value. ~ above your basic chemistry exam formula sheet, girlfriend will see them together equalities wherein opposite sides of the equal sign are a provided measurement expressed in different units:

1 inch = 2.54 centimeters

1 yard = 3 feet

1 foot = 12 inches

I’m sure that if you were asked to calculate the number of centimeters in 4 inches, you’d have the ability to calculate it with no problem. If one inch equals 2.54 centimeters, then 4 inches amounts to 4 time 2.54 centimeters. Easy. Part conversions space not this intuitive. Specifically when lock require an ext than one conversion aspect to get to the unit of measurement you interested in. The factor-label method is a foolproof way to execute conversions.

The scientific research behind the factor-label method

First points first, the switch factor, initially given to you as an equality, needs to be composed as a fraction. What side of the equal authorize goes in the numerator and also what next goes in the denominator? the depends! yet we’ll acquire to that soon. For right now, what’s vital to know is the both fraction possibilities, reciprocals the one another, space valid. Why is this?

Consider the switch factor: 1 customs = 2.54 centimeters.

Two fractions have the right to be make from this:



In both fractions, the numerator and also denominator room equal quantities. Thus, these two fractions equal one another and both space equal to 1.


The surname of the factor-label an approach game is to main point the worth you are given, unit of measure included, by the conversion aspect in portion form. Remember exactly how I said conversion factors do not adjust the worth of a unit that measurement? The factor-label method endorses this. The fraction you are using to execute multiplication through is same to 1! we all know any kind of value multiply by 1 is the very same value. The just thing that will change is the unit the measurement.

So, let’s lastly get right into the nitty-gritty of the factor-label method. Your setup will constantly have the following pattern:


Recall that the fraction portion is your conversion factor and that it is same to 1. We can now answer the question about which fraction we use since there will always be 2 possibilities. Her goal is the cancel the end the unit of measure you room no longer interested in. Whatever unit girlfriend are offered to start with will overview what portion you use. In various other words, you want the unit you are offered to start with to be in the denominator. In law this, you will certainly be left with the unit girlfriend want.


So, making use of the factor-label method, how many centimeters room in four inches?


When plugging this right into the calculator, divide the product of every the worths in the molecule by the product of every the values in the denominator. You deserve to think the the 4 in the problem over as 4 end 1 to help you visualize just how to multiply.

Some concerns to asking before setting up:

What units have I been given to begin with?What units have actually I to be told come find?What conversion factors have ns been provided to get from 1 come 2?

On a typical general chemistry test formula sheet, you’ll uncover a plethora that conversion factors – several of which you won’t even need. As a ascendancy of thumb, the conversion components you will usage will save on computer the systems you have been offered to begin with and/or the units you have actually been told to find. Maintaining this in mind will protect against you from gift overwhelmed through the formula sheet.

The first conversion element you usage must have actually the devices you have actually been offered to start with since your first goal is to cancel the unit out. If the various other unit in that conversion variable happens to it is in the units you have actually been told to find, you lucky and also only need to multiply making use of one fraction. However, this is not constantly the case. The number of fractions you’ll need to multiply in her setup counts on what conversion determinants are obtainable to you.

Here’s what i mean:

Suppose you desire to recognize how plenty of feet space in 4.6 miles.

In one instance you are given the complying with conversion factor(s):

1 garden = 3 feet, 1 mile = 1760 yards

Which conversion factor would you begin with? The one that has miles! exactly how should the fraction be written? with miles in the denominator!


In another situation, friend are provided the complying with conversion factor(s):

1 mile = 5280 feet


Both setups gained us to the same answer but detailed different conversion determinants to use. One required us to use 2 conversion factors/fractions due to the fact that no conversion aspect was given that directly attached the devices we began with to the devices we wanted.

Conversions can acquire quite involved and also require united state to usage three, four, five conversion factors/fractions. This no matter due to the fact that you are merely multiplying by 1 repeatedly. Numerous general chemistry calculations have the right to be used with the factor-label an approach alone.

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To summarize, switch that only require one step/conversion element tend to be easy yet for those that require multiple steps, the factor-label an approach allows friend to stay clear and also organized. The factor-label technique also enables for girlfriend to always know where to at the very least start in a conversion. Remember, cancel out the unit you started with and also go indigenous there. Learning where to begin will give you the confidence and clarity to watch where to walk next. Lastly, it makes checking your work easy.

Questions to ask yourself as soon as checking her work:

Did the systems I needed to release out in reality cancel out?Did i miswrite my conversion factor/fraction?