Is There a Relationship Between Density and Boiling Point?

In summary, the boiling point of a substance is the temperature at which its vapor pressure equals the surrounding pressure, causing it to change into a vapor. The density of a substance does not have a direct relationship with its boiling point, but molecules with similar chemical bonds and higher density tend to have higher boiling points. Other factors that affect boiling point include the weight of the molecules, strength of attractive forces between molecules, and outside atmospheric pressure.
  • #1
SuperSandwich
2
0
Just a random question. Is there a specific relationship between density and boiling point? If there is, what is it and why do they relate?
 
Physics news on Phys.org
  • #2
In general I don't think there is. I believe that molecules that have similar type of chemical bonds (e.g. covalent bonds) in general will have higher boiling points as the density of the pure substance increases.
 
  • #3
There are two things that play a major role in the boiling point of substances

1: how heavy are the molecules.
2: how strong are the attractive forces between molecules.
 
  • #4
One additional factor is outside (atmospheric) pressure.

From Wikipedia, the free encyclopedia


Boiling water
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid[1][2] and the liquid changes into a vapor.

A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high-pressure has a higher boiling point than when that liquid is at atmospheric pressure. In other words, the boiling point of a liquid varies depending upon the surrounding environmental pressure. For a given pressure, different liquids boil at different temperatures.
 
  • #5


Yes, there is a relationship between density and boiling point. Density is a measure of how tightly packed the molecules of a substance are, while boiling point is the temperature at which a substance changes from a liquid to a gas. The relationship between density and boiling point can be explained by the kinetic molecular theory, which states that as the temperature of a substance increases, the molecules gain more energy and move faster, causing them to spread out and take up more space. This results in a decrease in density. On the other hand, as the temperature increases, the molecules also have a higher chance of overcoming intermolecular forces and escaping into the gas phase, resulting in a higher boiling point. Therefore, there is an inverse relationship between density and boiling point - as density decreases, boiling point increases. This relationship can also be seen in the phase diagram of a substance, where the boiling point is typically higher at lower densities.
 

1. What is density and how is it measured?

Density is a measure of how much mass is contained in a given volume of a substance. It is typically measured in units of grams per cubic centimeter (g/cm^3) or kilograms per cubic meter (kg/m^3). To measure density, the mass of a substance is divided by its volume.

2. How does temperature affect density?

Temperature can affect the density of a substance because most substances expand when heated and contract when cooled. This means that as the temperature of a substance increases, its volume will also increase, while its mass remains the same. This results in a decrease in density. Conversely, as the temperature decreases, the volume decreases and the density increases.

3. What are some examples of substances with high and low densities?

Substances with high densities include metals such as gold, silver, and lead, as well as liquids like mercury and molten iron. Substances with low densities include gases like helium and hydrogen, and light materials like foam, cork, and wood.

4. How does boiling point relate to density?

Boiling point is the temperature at which a substance changes from a liquid to a gas. Generally, substances with high densities also have high boiling points, while substances with low densities have low boiling points. This is because substances with high densities tend to have stronger intermolecular forces, making it more difficult for them to change from a liquid to a gas state.

5. Can density and boiling point be used to identify substances?

Yes, density and boiling point are physical properties that can be used to identify substances. Each substance has a unique density and boiling point, and these values can be compared to known values to determine the identity of an unknown substance. This is often used in chemistry and forensics to analyze and identify different substances.

Similar threads

  • Other Physics Topics
Replies
15
Views
2K
  • Other Physics Topics
Replies
14
Views
2K
  • Thermodynamics
Replies
14
Views
608
Replies
3
Views
1K
Replies
13
Views
1K
  • Other Physics Topics
Replies
2
Views
1K
  • Other Physics Topics
Replies
5
Views
6K
Replies
3
Views
988
  • Other Physics Topics
Replies
2
Views
1K
Replies
0
Views
198
Back
Top