Unit Conversion & Dimensional Analysis | How to Pass Chemistry
21 Comments


In this video you are going to learn
everything that you need to know to finally conquer conversions. Alright
let’s do this! [Music Playing] Hello Hello Melissa Maribel here and I help students like
you understand what you just learned in class so you stress less and you
graduate faster so if you’re new here consider subscribing. Dimensional analysis,
conversion factors, conversions, unit conversions, [Sigh] All that means is going from
one unit to the next. These are the most common conversion factors that are
specific to length, mass, volume and time. In the description box below you’ll find
a link that allows you to actually access the same conversion factors. Let’s
go ahead and jump into our first example the mass of a frisbee is 125 grams
convert its mass to ounces using the conversion factor one ounce
equals twenty eight point three four nine grams you’re given is the 125 grams
this one is so nice to actually give you the conversion factor of one ounce is
equal to this amount of grams and we are finding our ounces.The plan is to go from
grams to ounces the proper setup is having your given on top diagonally we’ll
place the grams across from each other so our units will cancel. Grams would
then cancel and we’d be left with our ounces. You just divide these two
numbers. You end up getting four point four zero nine ounces however our given
was three sig figs we need to round up Your final answer is that four point four
one ounces. Moving on to example two using two conversion factors.
How many minutes will it take to drive to LA from San Francisco if a speed of
72 miles per hour is maintained the distance between the two cities is 405
miles first start with identifying
you’re given conversion factor or factors and what you are finding you’re
given is the 405 miles our conversion factors. We’ll start with the 72 miles
per hour so per hour just meaning that it is for
every one hour from there we need to convert to minutes so we’ll need the
conversion factor of 1 hour equaling 60 minutes because we are then finding
minutes. Your plan is starting with you’re given the miles we’ll convert
that to hours using the first conversion factor then from there taking our hours
and going to minutes using our second conversion factor. The set up is starting
with your given we’ll have our miles on top we want to match those miles on the
bottom so they can cancel. Note that these miles will then cancel and we’ll
have hours now on top you want to cancel out our hours we’ll put them across from
each other now they cancel as well and we’re left
with minutes multiply straight across and divide by that 72. You get three
hundred and thirty seven point five minutes however we have three
significant figures so we round up your final answer is three hundred and
thirty-eight minutes. Let’s look at our last example. A patient needs 50
milligrams of a medicine three times a day. If each tablet of medicine contains
25 milligrams, how many tablets will the patient need for a four-day prescription?
As always you want to go ahead and start with identifying your given, conversion
factor or factors and what you are looking for. The given is that 50
milligrams three times everyday conversions factor is that one tablet is
equal to 25 milligrams where we saw that that said each tablet of medicine
contains 25 milligrams and lastly you are finding the total amount of tablets
in that four-day prescription Step one is to multiply your given by
three take the 50 milligrams and multiply it by the three times per day and our
actual given is 150 milligrams per day The next plan is taking our milligrams
per day and changing that to tablets. The proper setup will have our new given the
150 milligrams per every one day. Next you want to match the milligrams to
cancel them out, we’ll place them across from each other using our conversion
factor. The milligrams will then cancel and now we have tablets per day
divide the 150 divided by 25 and you get six tablets per every one day. We
got that here with our tablet per every day. The last step is then to multiply
by four using the six tablets per every day we’ll cancel out our days putting
them across from one another six times four then gives us 24 tablets.
Grab a pen and paper and try these practice problems [Music Playing] How was that? For conversions I do
recommend practicing as many problems as possible! In the description box below
there’s a link with practice problems and step-by-step answers. Make sure to
check that out if you really want to ace your exam. Make sure you like this
video if you learned something and subscribe if you want to see more videos
just like this one and remember I am here to show you how to pass Chemistry!
So leave a comment below letting me know what you need help with and I’ll
see you next time. Grab a pen and paper Grab a pen and paper and write these practice problems [Laughs] down. [Laughs] Okay. Grab a pen and paper and try these practice problems [Laughs] Grab a pen and paper and try these practice problems….Straight face

21 thoughts on “Unit Conversion & Dimensional Analysis | How to Pass Chemistry

  1. Melissa tutored me in college algebra for a year and with her help I succeeded in achieving my first ever 4.0 GPA she helped make sense of concepts that I had trouble with. When I needed extra help on a concept we spent time going over it until I felt confident with it. With her help I had a very successful year and Melissa is very accommodating. She also always has more than one way to teach the same thing for those who learn in different ways. I would always recommend her to anyone that needs help in math or chemistry.

  2. What do you do if the conversion is not given to you? And you don't have it memorized? My teacher won't give us conversations on any of the tests

  3. where can i download your notes? and hoping you can still upload the practice problems that way i can practice for my exam

  4. So after you have done the conversion you only round to the significant numbers of the original number? For example in the video you multiplied 60*405, but rounded it up to 3 sigfigs when 60 has the least sigfigs.

  5. Here's another updated video to help you with Unit Conversion: https://www.youtube.com/watch?v=7voNNBbMcxE

  6. Thank you soooooo very much. I was struggling understanding how to set up the problem and which factor to use and this completely helped me. I really really really really am soooo grateful that you did this video. You made it sooo much easier to understand.

  7. thank you SOOO much!!! I'm so close to the chemistry regents, but I don't know anything. Thanks to you, I finally get the hang of it. Wish me luck!!!

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