Problem involving mercury thermometer

[xnitexlitex]

Homework Statement

A mercury thermometer contains 7.5 mL of mercury. If the tube of the thermometer has a cross-sectional area of 1.2 mm², what should the spacing between the °C marks be? (The volume expansion coefficient for mercury is 1.81 x 10^-4 °C⁻¹.)

Homework Equations

ΔV=βV₀ΔT

The Attempt at a Solution

I set ΔT = 1, converted the mL into mm³.

I got ΔV = [5.43*(10^-4)](7500)(1) = 4.0725 mm³.
However, I don't know what to do with the area!

 

[daveb]

What do you get if multiply the cross sectional area by the change in height?