Question

I was wondering if you would be able to help me with Solids, liquids, gases and their relations to IMFs. I am an AP Chemistry high school student and have a test tomorrow. Here is an example question 1. As we increase the temp. of a liquid, its properties change. Which of the following would not be an expected change om the properties of a typical liquid as we increase its temperature. a. decrease in viscosity b. decrease in density c. increase in surface tension d. increase in vapor pressure I know the answer is C, but I don't understand why. P.S. would you have any study tips when it comes to IMFs and problems like this?

Answer 1

Liquid as its temperature raised, it ganis more kinetic energy and this will partly tries to break the intermolecular force(imf) and thus the molecules will go more and more far away as the temperature is increased. Thus the volume will increase(of the sample).

A.

Viscosity is the difficulty of flowing. If imf is stronger, sample have high viscosity, it will be hard for them to flow. As other molecule attracts, so prevent one molecule moving(flowing).

As temperature increased, imf decreases and viscosity decreases.

B.

Density is the ratio of mass to the volume occupied.

So density is inversely proportional to volume.

As temperature increased, imf decreases, volume increases.

Due to inverse relationship of density with volume, density decreases.

C.

Surface tension is also like measure of imf between the molecules. But on the surface of liquid sample. If temperature is raised, imf will decrease and thus surface tension should decrease.

D.

Vapour pressure is the pressure exerted by the vapour.

Liquid at any temperature evaporates and forms vapour. The rate of evaporation increases with temperatures. Reason is that molecules seperate from other molecules and goes to vapour phase easily if imf is reduced.

Connect the different properties of liquid with its imf and have an idea about whats happening at the molecular level in each properties.