Posted by
**bex** on
.

if i am trying to find the diameter of an oil molecule and express my answer in scientific notation.

the info is drop of oil 0.05 cm3 from a dropper spreads out to 40 cm2

is it

vol = l x w x h

0.05cm3 = 20 x 20 xh

0.05 cm3 = 40cm2

after this im stuck as i don't know what the size of the oil molecule is

can anyone help

vol = l x w x h

0.05cm3 = 20 x 20 xh **OK TO HERE.**

0.05 cm3 = 40cm2 **You threw away the h which is the unknown here.**

after this im stuck as i don't know what the size of the oil molecule is

can anyone help
**Oh, but you do know the size of the oil drop. It has a volume of 0.05 cm ^{3} or 0.05 cc. Says so in the problem.
You have 0.05 cc = lxwxh.
The problem states that the oil drop spreads out to an area of 40 cm^{2}. That is lxw. Now the eqution is
0.05 = 40*h
solve for h.
I think i have managed it
0.05cm3 = 40 x h
h = 0.05/ 40
h = 1.25 x 10-3cm3
is this correct please
im trying to help my daughter out on this i think i need to go back to school lol
Correct if you aren't worried about the number of significant figures. There are only two s.f. in 0.05 and two in 40 (if it is 40. and not 4 x 10^1); therefore, you are allowed only two in the answer and 1.25 has three. You must round it, if s.f. are a concern, to either 1.3 x 10^-3 or 1.2 x 10^-3 depending upon how your instructor has taught you to do it. I round to the EVEN number; therefore, I would round to 1.2 x 10^-3. A note about the 40. 40 with no decimal point after it has only one s.f., 40. has two. 4 x 10^1 has one. If the 40 has only one s.f., then 1 x 10^-3 is the answer. **