College student. Should I memorize

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Memorizing key conversion factors is essential for success in college-level chemistry, as exams may not always provide them. Students are advised to focus on common conversions like 1 meter = 100 centimeters and 1 mile = 5280 feet, while also understanding metric prefixes like kilo- and centi-. It's noted that while some conversions may not appear on exams, having a general sense of sizes and relationships in measurements is beneficial. Additionally, students should practice solving problems to reinforce their understanding of conversions and avoid confusion under pressure. Ultimately, committing essential conversions to memory can enhance performance in chemistry courses.
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guys should I memorize the conversion ex, 1 this equals that? Or will they ALWAYS be provided on exams? I don't want to take the risk. If there are teacher who won't provide it, I don't want to take the chance I want to commit it to memory now. At the moment I'm studying the basics of Chemistry and ALL the practice problems I've been doing online provide it. So let's say they give you foot and they want meters as your final answer they will give you the scale ex this equals this amount of meters.

I'm preparing for Chem I (General Chem) at the college level so anyone who has passed me just let me know if this is something I should memorize.

thanks in advance
 
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Never seen a units conversion on an exam question - they are normally confusing because they go out of the way to use consistent units so you end up with m^3 where you would have expected litres or cc in the lab.

It is worth having an idea of general sizes of things, how big is a mole of ideal gas or a mole of a common salt - just so you know if you a factor of a million wrong somewhere
 
NobodySpecial said:
Never seen a units conversion on an exam question - they are normally confusing because they go out of the way to use consistent units so you end up with m^3 where you would have expected litres or cc in the lab.

It is worth having an idea of general sizes of things, how big is a mole of ideal gas or a mole of a common salt - just so you know if you a factor of a million wrong somewhere

so do I memorize or not? Also let me know where to start or what to start with
 
Don't memorize feet to meters etc
Do memorize m^3 to cm^3 and litres - it's surprisingly easy to get wrong under pressure
 
NobodySpecial said:
Don't memorize feet to meters etc
Do memorize m^3 to cm^3 and litres - it's surprisingly easy to get wrong under pressure

alright thanks, man :cool:
 
You will know which conversion ratios to memorize. Knowing that is intuitive based on what you study and the exercise problems you solve. Along with memorizing some essential conversion ratios, you must know what they mean.
 
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symbolipoint said:
You will know which conversation ratios to memorize. Knowing that is intuitive based on what you study and the exercise problems you solve. Along with memorizing some essential conversion ratios, you must know what they mean.

was looking through an old test (the semester is over). Here are questions:

5. Convert 1.345 miles to feet

She didn't give us a key (this amount of miles equal this amount of feet) so in a case like this if I don't have how many miles = feet memorized, what do I do? How would I go about solving it and it's not given to me.

Another question:
How many centimeters are there in a cubic meter?

what about this case? What do I do? so do you see what I was saying with the memorization? Lastly, I'm sure you're familiar with this table:
"[URL
http://voltammetry.net/_media/pine/aftermath/user/metric_prefix.jpg?w=&h=&cache=cache

how do you manipulate it?
 
Last edited by a moderator:
Responding to post #7:

You would want to lookup feet per mile in either a handbook, an almanac, or a reference page of a dictionary (yes, these are often in dictionaries). I memorized the specific fact when I was very young; you should be able to find 5280 feet = 1 mile. I just know it, and I do not need to look for the fact in a reference material.

How many centimeters in a cubic meter? You cannot compare length to volume. Did you mean cubic centimeters, or did you mean in a meter? You only need simple understanding how the prefixes of the metric system work. Those prefixes you must memorize. Note the prefix meaning, centi- means multiplied by 0.01.
 
I think it might be a good idea to know some of the more common conversions (i.e. 2.54 cm in 1 inch) although not you probably won't need them for exams. I would ask your professor if these things will be expected, but otherwise it's just useful so that you have a general idea of the relative sizes of things, like someone said before.
 
  • #10
Edin_Dzeko said:
5. Convert 1.345 miles to feet
so in a case like this if I don't have how many miles = feet memorized, what do I do? How would I go about solving it and it's not given to me.
You can't - it's not a physics question. It's like asking what TV program is on before Jay Leno in Philadelphia

Unless of course you are into medieval history and have memorized that a mile is eight furlongs; each furlong is ten chains; each chain is four rods/poles/perches and a rod is 5.5 yd
 
  • #11
You should memorize basic information like 100 cm = 1 meter or 8 fl oz = 1 cup or 5280 ft = 1 mile and so forth.
 
  • #12
chemisttree said:
8 fl oz = 1 cup or 5280 ft = 1 mile and so forth.
Cookery maybe - but for a science class?
 
  • #13
Yep. If you don't yet know that there are 5280 ft in a mile or 8 fl oz in a cup, (and you live in the US) you probably aren't cut out for science, IMO. Maybe a business major or an accounting major.

There are other conversions that you will need to learn when taking a college-level science course. Converting feet to meters is one of them.

And teachers absolutely hate this sentiment...
If there are teacher who won't provide it, I don't want to take the chance I want to commit it to memory now.
... which to a teacher would translate to something like, "Why should I do my best? I have budgeted limited time to this task so tell me just how little effort I can get by with."
 
  • #14
chemisttree said:
... which to a teacher would translate to something like, "Why should I do my best? I have budgeted limited time to this task so tell me just how little effort I can get by with."
You have to be selective in what you memorize though.
Knowing that an ideal gas is 22.4l/mol at STP and 24l/mol at room is useful, knowing the entire periodic table or avagadro's number to 10places is less so.

I assumed that even in the US science was done in metric - except for the occasional Nasa 'administrative error' - so reciting how many feet in a rod, chain, furlong, mile and oz, pints, gallons, barrels, hogsheads, tuns was all in the past
 
  • #15
Okay I'm back. So after more practicing and fooling around. I learned something today. The solution to my memorization dilemma:

Turns out this is the solution:
=================================
Prefix...Symbol...Value
Mega-....M...10^6
Kilo-...k....10^3
------------------------------------
deci-...d....10^-1
centi-.....c.....10^-2
_*it's not necessary to list whole table_
=================================

so is it a good idea to commit this to memory? with this I can now face questions like:
"Convert 75m into cm" without having how many m=cm memorized. Because knowing the table above helps with the conversion.

Also the teacher noted some key things: "Remember 1mL = 1 cm^3 or 1L=1dm^3)"

Yay! So happy :biggrin: what a load of my back :cool:
-------------------Answers to forumers:-------------------------------------
"Yep. If you don't yet know that there are 5280 ft in a mile or 8 fl oz in a cup, (and you live in the US) you probably aren't cut out for science, IMO. Maybe a business major or an accounting major." - chemisttree

Yeah, my science and math background aren't that good that's why I'm trying to cover the basics so I won't struggle when I begin class (or at least suffer for not knowing the simple things). :redface: I'll consider what you said and commit it to memory. Thanks.


"You have to be selective in what you memorize though.
Knowing that an ideal gas is 22.4l/mol at STP and 24l/mol at room is useful, knowing the entire periodic table or avagadro's number to 10places is less so." - NobodySpecial

that's the reason why I came on here to ask you more advanced guys. I'm a total noob to science and like I said my background's really bad. So if you could help me and point me in the direction of what will be useful to memorize you'd save me from memorizing something useless
-------------------------------------------------------------------------------

Closing question(s):

Now I understand not everything will be on the units and prefixes chart that I mapped out above. Most of you have been throwing feet -> miles and inches to feet.

Ex:
Convert 87km into miles. I don't have miles on my chart and mi isn't a prefix whereas k is. For this particular problem however 1mi=1.609km was provided and I've understood the conversion concept well enough to be able to get the answer when such information is provided. So is this the case where I should memorize how many km = a mile and how many feet = a mile? I know 12 inches = a foot :D

Thanks for your help so far guys. I appreciate it.
-------------E-D-I-T-----------------------------
So here's what I have a list of things to commit to memory (aside the prefix chart):

LENGTH:
1 foot = 12 inches
1 yard = 3 feet
1 miles = 5280 feet

WEIGHT:
1 pound = 16 ounces
1 ton = 2000 pounds

CAPACITY:
1 cup = 8 fluid ounces
1 pint = 2 cups
1 quart = 2 pints
1 gallon = 4 quarts
 
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  • #16
Edin_Dzeko said:
Prefix...Symbol...Value
Mega-....M...10^6
Kilo-...k....10^3
------------------------------------
deci-...d....10^-1
centi-.....c.....10^-2
_*it's not necessary to list whole table_
=================================

so is it a good idea to commit this to memory?

Definitely, they are universal - they are present in every science, where you have to deal with numbers very large and very small.
 
  • #17
Stump at a simple problem

Okay here's what I'm confused with:

Convert 3.50 Liters to mL:

so 10^-3 mL / 1 Liter and 1 Liter / 10^-3 mL

so:

......10^-3 mL
3.50 Liters...--------------
......1 Liters...

Liters cancel and it becomes 3.50 x 10^-3 = .00350 mL but checking the solutions I got
3500 mL instead of .00350 mL. What's wrong? Someone explain it to me.

Also I looked on google and got: 1 liter = 1000 milliliters so is the 10^-3 the mistake here? The paper I got it from wrote it as 10^-3 for milli (m)

thanks in advance.
 
  • #18
1 mL = 10-3L, so 1L = 1000 mL.
 
  • #19
Here's another one:

Convert 8.7 cm to mm:

cm --> m --> mm

.....10^-2 m 1 mm
8.7 cm --------- x --------- = .000087 mm or 870000 mm
.....1 cm...1000 m

but the solution said it was 87 mm I understand that's due to the fact that 8.7 has only 2 significant figures. so if I wrote down 870000 mm on a test would that be marked wrong? 870000 mm is still 2 significant figures but it's values are different.

I'm not sure about the conversion of milli. I used 1 mm / 1000 m instead because 1 L = 1000 mL and I got 8.7x10^-5. that's why I put 000087 or 870000 wasn't sure which because I'm not sure about the calculation of milli

is my calculator behaving weird or what?
 
  • #20
Borek said:
1 mL = 10-3L, so 1L = 1000 mL.

that's what I used. 3.50 x 10^-3 = 3.5 x 10^-3. don't you move the decimal to the left because of the negative? which would make it .0035? or do you move the decimal to the right which would make it 3500?
 
  • #21
No, that's not what you did.

1mL = 10-3L doesn't mean 10-3mL/1L but 1000mL/1L.

Look:

1mL = 10^{-3}L

You want 1L on the right, so divide both sides by 10-3:

1/10^{-3}mL = 10^{-3}/10^{-3}L

or

1000mL = 1L

Think this way: milli means 1/1000th, so mL is much smaller than 1L. If so, it can be 10-3mL/1L, it must be many mL per 1L.
 
  • #22
Borek said:
No, that's not what you did.

1mL = 10-3L doesn't mean 10-3mL/1L but 1000mL/1L.

Look:

1mL = 10^{-3}L

You want 1L on the right, so divide both sides by 10-3:

1/10^{-3}mL = 10^{-3}/10^{-3}L

or

1000mL = 1L

Think this way: milli means 1/1000th, so mL is much smaller than 1L. If so, it can be 10-3mL/1L, it must be many mL per 1L.

Oh ok. Nice catch, bud. I see where the mistake was/lies.

I fixed it and now see how the answer works:

3.50 L x 1 mL / 10^-3 L = 3500 mL

thanks, bud. I see it. so when you're converting it's:

1 (prefix)(unit) = 10^(value of prefix & symbol)(unit)

so for instance how many meters are in a kilometer:
1 (kilo)(meter) = 10^(3)(meters)
 
  • #23
Edin_Dzeko said:
1 (kilo)(meter) = 10^(3)(meters)

Right.
 
  • #24
Two things:

[1] Convert 8.6 g/mL to lb/gal the answer is 72 lb/gal. But how do you get that? can you write it out?

Here was my attempt:

.....1..lb.... .00025 gal
8.6 g/mL x ----------- x ---------- = 1.1 lb/gal
.,,,,,,,,,,,,,,, .00220 g,,,,,,,,,,,,,,1 mL

Where is my mistake what did I do wrong?

===================================================

[2] d = .789 g/mL and v=150 mL

150 mL x __.789g____ = 118 g
......mL

my question is shouldn't it be 1.2 x 10^2? 150 is only 2 sig figs while .789 is 3 so shouldn't the answer be in 2 sig figs?

or did the author of the work forget to put a "." after the 150?
 
  • #25
No idea where did you get 1 lb/0.00220 g.

Most likely 150 is three sig figs, 1.5x102 would be two. But I understand your confusion, sometimes notation is not clear. Significant digits are faulty by design, don't treat them too seriously.
 
  • #26
Borek said:
No idea where did you get 1 lb/0.00220 g.

Most likely 150 is three sig figs, 1.5x102 would be two. But I understand your confusion, sometimes notation is not clear. Significant digits are faulty by design, don't treat them too seriously.

How would I solve it then? I got 1lb / .0020 g from the web.

1 lb = 454 g
1 g = .0020 lb

(according to google)

is it wrong? How would I solve problem [1]? can you set it up for me at least?
 
  • #27
Edin_Dzeko said:
Two things:

[1] Convert 8.6 g/mL to lb/gal the answer is 72 lb/gal. But how do you get that? can you write it out?

As well as Borek's comments, bear in mind that PF is international - what is your gallon? http://en.wikipedia.org/w/index.php?title=Gallon&oldid=402659177

(though this is not strictly a sf issue)
 
  • #28
Edin_Dzeko said:
1 lb = 454 g
1 g = .0020 lb

This is exactly opposite to

1lb / .0020 g
 
  • #29
Chemical and Physical properties:

I'd like to know if the answers to these are correct:

Water Boils at 100 C -------------------------------------Physical
Color of fabric -------------------------------------------Physical
Polymerization (example: commercial glue) -----------------Chemical
Mass of certain amount of Fe -----------------------------Physical
Magnet separate iron shavings & white sand ---------------Physical
Decomposition of Hydrogen perox. when exposed to light ---Chemical
Burning a log ---------------------------------------------Chemical
Boiling egg (turning hard) ---------------------------------Chemical
Slicing bread ---------------------------------------------Physical
Ice cream melting ----------------------------------------Physical
Density of glucose ----------------------------------------Physical
 
  • #30
Please start new threads when asking new questions.

In general your answers are right, but if that's how the question was posted... sigh.

Boiling point is a property, OK. Burning of a log is NOT a property, it is a process. Some of processes presented are a combination of physical and chemical changes, so they are difficult to classify.
 
  • #31
Borek said:
Please start new threads when asking new questions.

In general your answers are right, but if that's how the question was posted... sigh.

Boiling point is a property, OK. Burning of a log is NOT a property, it is a process. Some of processes presented are a combination of physical and chemical changes, so they are difficult to classify.

[1] Oh ok. I'd really like that. I just thought I would get flamed by the others for opening many threads. But thanks. Now that I have your approval I'll freely go ahead and do so.

[2] Yep that's exactly how they were asked. :smile:

Thanks, bud. I appreciate it.
 

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