# Heat Capacity/ Density/ Conductivity

• Skyeagle
In summary, the conversation discusses the role of heat capacity, density, and conductivity in the melting process of materials. The participants also mention the importance of thermal diffusivity, which is determined by these variables. The thermal conductivity governs the speed of heat transfer through conduction, while density and specific heat affect the temperature change with heat. It is noted that thermal diffusivity is an exact function of thermal conductivity, density, and specific heat.
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.

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

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.

minger said:
The thermal conductivity $$k$$ governs how fast heat is transferred through conduction.
$$q = kA \frac{dT}{dx}$$

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:
whoops, my mistake. Good catch!

## 1. What is heat capacity?

Heat capacity is a measure of the amount of heat energy required to raise the temperature of a substance by a certain amount. It is typically measured in units of joules per degree Celsius (J/°C) or calories per degree Celsius (cal/°C).

## 2. How is heat capacity different from specific heat?

Heat capacity is an extensive property, meaning it depends on the amount of substance present. Specific heat, on the other hand, is an intensive property and is independent of the amount of substance present. It is defined as the amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

## 3. What is density?

Density is a measure of the mass of a substance per unit volume. It is typically measured in units of grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³). In simpler terms, it is a measure of how tightly packed together the molecules of a substance are.

## 4. How does density affect the buoyancy of an object?

Density plays a crucial role in determining the buoyancy of an object. An object with a higher density than the fluid it is placed in will sink, while an object with a lower density will float. This is due to the upward force exerted by the fluid, known as buoyant force, being greater than the weight of the object.

## 5. What is thermal conductivity?

Thermal conductivity is a measure of a material's ability to conduct heat. It is defined as the amount of heat energy that can pass through a unit area of a material in a unit time when a temperature difference exists between the two sides. It is typically measured in units of watts per meter Kelvin (W/mK) or kilocalories per meter hour degree Celsius (kcal/mh°C).

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