# Math Help - For Chemistry, Please help

1. ## For Chemistry, Please help

just a little rusty on the conversion side of maths at the moment, so was wondering about this question:

'An ice cube is 2.00 in. on a side and weighs 1.2*10^2 grams.

a) what is the density of the ice?
b) what volume of water (d=1.00g/ml) is obtained when the ice cube melts?'

I have attempted part a, but never got the real answer (which is 0.916g/cm^3)

so here is what I was starting:
d=mass/vol.

mass = 1.20*10^2g

converting in. to cm: 1in. = 2.54cm
therefore 2in. * (2.54cm/1in.) = 5.08 cm.

therefore vol.= pi(5.08)^2(5.08)
= 411.85

so d=mass/vol.

1.20*10^2g/411.85=0.291

I don't know what I have messed up, but if someone could help me understand, that would be appreciated!!

2. ## Re: For Chemistry, Please help

It's an ice CUBE.

3. ## Re: For Chemistry, Please help

so where should I 'cube' it?

4. ## Re: For Chemistry, Please help

A cube is a particular sort of rectangular solid, $\pi$ does not come into the calculation of its volume.

5. ## Re: For Chemistry, Please help

isn't the formula for the volume of a container V=pi(r^2)h?

6. ## Re: For Chemistry, Please help

That's the formula for the volume of a cylinder radius r and height h, not a cube.

7. ## Re: For Chemistry, Please help

ooh. could you please tell me what I am meant to do in the equation instead?

8. ## Re: For Chemistry, Please help

The only thing that you did wrongly was the calculation of the volume of the cube.
Suppose that you have a rectangular box, picture a shoe box say.
If its dimensions are a cm * b cm * c cm, what is its volume ?
For a cube, a = b = c.

9. ## Re: For Chemistry, Please help

so all that is, is 2in=2in=2in. how does that fit in? also, why and where do I change from in. to cm.?