# Homework Help: Density at certain temps

1. Oct 8, 2004

### nemzy

lets say for example the density for gasoline is 730 kg/m^3 at 0 degree Celsisus

Will the density be different for at a diff temperature, or will it always remain constant?

If it is different, how would you calculate it? thanks

2. Oct 9, 2004

### Spectre5

Density is mass per unit volume (well, mass density anyways)

So heating or cooling would change the density beucase the volume that the substance would change. There are a number of different ways to find the change in volume of the substance...depending on what form it is in, etc.

3. Oct 9, 2004

### nemzy

well for my homework question, it gives the avg coefficient of volume expansion. and from there on i have no idea how to calculate the density of gasoline at a diff temp.

4. Oct 9, 2004

### Spectre5

use the following equation:

$$\Delta V = \delta*V*\Delta T$$

Where $$\Delta V$$ is the change in volume, $$\delta$$ is the coefficient of volume expansion, V is the current volume, and $$\Delta T$$ is the change in temp

Edit: Changed symbols to Latex

Last edited: Oct 9, 2004
5. Oct 9, 2004

### nemzy

i know, but once u find the change in volume, how can u relate it to finding density at a certain temp?

for example, lets say density of gasoline is 730 kg/m^3 at 0 degrees

what will the density be at 20 degrees?

a gallon of gasoline occupies .00380 m^3 and the avg coefficient of volume expansion is 9.6e-4

So plugging it into the equation, i got a change of volume of 7.296e-5, with final volume being .00387296...now from here how would i be able to find the new density at the new temp?

6. Oct 9, 2004

### Spectre5

well, remember, mass density = mass / volume

you know the new volume...and you know the mass (hint: use the original density and the original volume to find the mass)