How does temperature affect viscosity and density?

Answer 1

Viscosity:

In gasses, forces between atoms are not important and the transfer of momentum (hence force, hence viscosity) between different adjacent regions of a fluid is due to the movement of particles over long distance. Higher temperature means faster movement means higher viscosity in a gas.

In liquids, forces between particles dominate and shear force is transmitted through those interactions with adjacent particles. Higher temperature means more short distance particle movement and more varied interaction with neighboring particles thus decreasing the effectiveness of transmitting shear force and decreasing viscosity.

(These trends in viscosity are only general and complex interactions of particles can produce different results than described here.)

Density:

If the pressure is held constant, an increase in temperature normally results in an increase in volume of a liquid, solid or gas. This parallels the explanation of how particle motion at the microscopic level produces pressure by collisions with the walls of the containing volume. More temperature means more energetic particles that have more momentum to transfer to container walls. With constant pressure, the walls expand.

(The obvious caveat here is that molecular orientations and molecular forces can be complex and this connection between increased temperature and decrease density is not universally true. The properties of water between 0 Celsius and 4 Celsius are a well known counter example to the general rule.)

Answer 2

This is a great question, because the two are easy to confuse. Density is mass (or weight) per volume. Viscosity is how fast a substance flows through a hole driven by a given force (usually gravity). A substance like Mercury can be very high density and low viscosity. A substance like whipped cream can be very low density and very high viscosity. One of the confusions is that viscosity is not changed by altitude (pressure). Even though the atmosphere's density is extremely low at high altitude, the viscosity is about the same as at sea level.

Answer 3

the main cause for the viscosity is cohesive forces between the molecules.

here two cases arise.1)gases 2)liquids 1}in gases, temperature is directly proportional to viscosity.

this is because the cohesive forces between the molecules of gases are very small.

there fore there will be transfer of momentum between the molecules travelling with higher and lower velocities due to collisions.this momentum transfer is the main cause for viscosity in gases.exchange of momentum increases as temperature increases.hence viscosity increases as temperature increases .

2}in liquids,the temperature is inversely proportional to viscosity.

this is because as temperature increases then distance between the liquid molecules increases resulting in the decrease of the cohesive forces.therefore the viscosity decreases as temperature increases.

Answer 4

no that's imposible

a substance can either have low or high viscosity

Answer 5

If a liquid is more dense than another and the two are mixed, the denser liquid will settle to the bottom and the less dense liquid will "float" above

Answer 6

Liquids become more viscous as they become cooler.

Answer 7

no

Answer 8

Yes, der

Answer 9

Yes!