change because of temperature

Question

An aluminium rod has a length of exactly one meter at 300K. How much longer is it when placed in a 400°C oven?

I've been told the answer but not sure how to get to the answer 

Answer 1

You need to look up the coefficient of thermal expansion of aluminum. 

 

L₀ = length at 300 K

L = length at 400°C (i.e. at 573 K)

α = coefficient of thermal expansion of aluminum (look it up)

ΔT = temperature change

 

Then

 

L = L₀(1 + αΔT)

 

Plug in the numbers, and be careful with units.