Beginning Chem unit conversion help

[~Pi(~3.14)]

Hey, got a question here for my chemistry class...and its got me stumped. How would you go about doing this? any help? need to have it done by tonight!!


8.A copper wire (density = 8.96 g/mL) has a diameter of 0.42 mm. How long (in cm) would 24 g of this wire be?

[dbqinsa]

It is just the unit conversion that you're having trouble with?

[LaughingSkull]

1 mL = 1000 cubic mm

that should be enough, otherwise you suck :P

[~Pi(~3.14)]

could you just outline the operations for me? cuz im not getting it.

[bluedot]

Density is mass / volume: p = m/v

The volume of a cylinder is a function of diameter and length... Write that equation out and put it in the first equation. Then solve for the only thing you don't know.

If it's just the units that are troubling you, you need to work on metric prefixes. For instance, 1 m = 100 cm = 1000 mm. To get that in a volume, 1 m^3 = (100)^3 cm^3 and so on.

Does this answer your question?

[Elven_Lord]

a copper wire is a cylinder with volume = (pi)(r)^2(L). You want to find L and you know volume and radius. The radius is 0.21 mm and the volume is 2.678 mL = 2.678 cm^3

Convert .21 mm to cm (.021 cm).

The answer is 1933.01 cm

[LaughingSkull]

sigh, and you even have a maths-inspired nickname :P

The formula for weight is volume times density. We already have the weight, it's 24 grams. And the density is 8.96 g/mL, which is 8.96g/1000mm^3, which is 0.00896g/mm^3.

Therefore volume is weight divided by density or 24g/(0.00896g/mm^3) = 2679mm^3 (rounded, forgot about significant digits)

Volume of a cyllinder is area of base times length. The area of the cross section of the cable is (0.21^2)*3.14 = 0.14 sq mm (rounded again; standard area of a circle formula).

Divide 2679 by 0.14 and you get the length in millimetres.

something like that.