I think it's 2 I tried looking it up because I was not sure.
(1) The melting of a crystalline solid is best depicted by the second graph. This is because, the second graph shows a horizontal line which means that for a while there was no change in temperature. This zone is the latent heat of fusion.
(2) The first graph shows the graph of a solid that is just heated but does not experience phase change. However, the second graph shows a solid that changes phase (from crystal/solid to liquid).
There are 5 significant figures in the following number. All of the numbers essentially are significant.
<u>Answer:</u> The temperature of the system will be 1622 K
<u>Explanation:</u>
The equation relating the pre-exponential factor and activation energy follows:
where,
D = diffusion coefficient = 
= pre-exponential constant = 
= activation energy of iron in cobalt = 273,300 J/mol
R = Gas constant = 8.314 J/mol.K
T = temperature = ?
Putting values in above equation, we get:
Hence, the temperature of the system will be 1622 K
Solids - particles are very close together (highest density on the list)
Liquids - the particles slide past one another
Gases - particles bounce off of surroundings and the same particles of the gas
