2. Let’s deal with prefix milli- , since we see
it quite often in Chemistry.
(unit of mass) gram g
(unit of volume) liter L
(unit of distance) meter m
1 gram contains 1000 milligrams → 1g = 1000mg
1 liter contains 1000 milliliters → 1L = 1000mL
1 meter contains 1000 millimeters → 1m = 1000mm
3. And 1 milliwhatever is one thousands
part of whatever it is :)
Too bad, something and whatever are
not basic units of metric system.
So, technically: 1 something contains 1000 millisomethings?
1 something = 1000 msomethings
If I collect and put on a scale 1000
milligrams of something. What would be the
reading on the scale? _____________1 gram
4. If I collect and pour together 1000 milliliters of
liquid in one big measuring cylinder, what
would be the overall volume of that liquid?
_____________
My pet caterpillar crawls 1 millimeter every
minute. It travels in a straight line. How far will
it go if it will crawl for a 1000 minutes without
rest? _____________
He will never catch up.
Freedom!!!
1 Liter
1 meter
5. What if my pet caterpillar was crawling for 3
hours and then went to sleep?
3 hours → 60 x 3 = 180 min
Speed : 1 mm/min ⇒ 180mm
What is it in meters?
Oh, I know, I know…
I have to multiply it by a thousand or divide?
Which one?!?
7. I have to multiply it by a thousand or divide?
Which one?!?
Any number can be multiplied by 1 without any
change to it. You want to get rid of millimeters. So,
make sure, they are in denominator in the
conversion factor, so they would get canceled out.
8. You have 10875.56mg of gold. Are you rich?
Convert it into grams...
I know: 1g = 1000mg
I want mg to cancel out…
About 11g of gold. I guess, I’m not that rich.
9. I have 3.75 L of water. What that would be in mL?
I know: 1L = 1000mL
I want L to cancel out, and L in numerator. So, I
must choose conversion factor with L in denominator!
10. Density of gold is 19.3 g/mL.
What would be this density in g/L?
I know: 1L = 1000mL
I want mL to cancel out, and mL in denominator. So,
I must choose conversion factor with mL in numerator!
11. Another unit of volume that Chem
students get to deal with: cm3
Great! (deep sarcasm)
What do I do with it?
Nothing special:
1mL = 1 cm3
What’s the trick?
The trick is not to overthink it. When converting mL
into cm3 and back, don’t cube anything, don’t take
cubic routes. Just change the unit - it is 1:1 ratio.
12. Convert 2.35 mL into cm3
2.35 cm3
Convert 28.77 cm3 into mL
28.77 mL
Convert 7.23 L into cm3
7.23 L → 7230 mL
7230 ml → 7230 cm3
Convert 252 cm3 into L
252 cm3 → 252 mL
252 ml → 0,252 L
13. My average stride is 58 cm.
What is it in meters?
1 gram contains 100 centigrams → 1g = 100cg
1 liter contains 100 centiliters → 1L = 100cL
1 meter contains 100 centimeters → 1m = 100cm
15. I want cm to cancel out and cm in numerator, I must
choose a conversion factor with cm in denominator .
Wow!
And what would that be in good old inches?
Do you know conversion factor for
meters and inches?
16. No. But I know that 1 inch is 2.54 cm.
First, I want to get rid of meters…
And now, let’s get rid of centimeters...
I could have done it in one go...
17. Kilo- is another prefix that you frequently get to
deal with in Chemistry and in Physics.
1000 grams make up 1 kilogram → 1000g = 1kg
1000 liters make up 1 kiloliter → 1000L = 1kL
1000 meters make up 1 kilometer → 1000m = 1km
19. Dimensional analysis is especially important in
Physics where you need to convert complex units…
Car is moving at 60 mph (mph → miles/hour)
What would it be in m/sec? (1 mile = 1.6km)
