# Heat Capacity/ Density/ Conductivity

1. Jan 25, 2009

### Skyeagle

Hi guys,

Just like to check with you:

How does heat capacity, density and conductivity plays a part in the melting of a certain material.

I mean, if a material has a lower heat capacity, while other factors are the same, does that mean it will melt faster compared to one with a higher heat capacity when exposed to the same amount of heat intensity?

Likewise for density and conductivity, how to they play a part in the melting of a certain material?

Thanks.

2. Jan 26, 2009

### Mapes

Look into thermal diffusivity, which governs how fast thermal energy propagates. It is connected to the variables you mention above.

3. Jan 26, 2009

### minger

Thermal diffusivity is important, but I think the OP wanted to know how the specific components affect the melting.

The thermal conductivity $$k$$ governs how fast heat is transferred through conduction.
$$q = kA \frac{dT}{dx}$$
Density and specific heat governs how the temeprature changes with heat.
$$\Delta T = \frac{Q}{mc}$$
With mass of course being related to density.

4. Jan 26, 2009

### Mapes

No, it doesn't; time doesn't appear independently in that equation. Although copper has a higher thermal conductivity than gold, for example, a temperature rise propagates faster in gold. In the heat equation

$$\frac{\partial T}{\partial t}=\alpha \frac{\partial^2 T}{\partial x^2}$$

(1-D shown for simplicity), the thermal diffusivity $\alpha$ (units m2 s-1) is an exact function of thermal conductivity, density, and specific heat. I wanted to let Skyeagle find the relationship on her/his own.

Last edited: Jan 26, 2009
5. Jan 26, 2009

### minger

whoops, my mistake. Good catch!