Chapter 17, Problem 2RAT

Imagine that you can see individual molecules. You watch a small collection of molecules that are moving around slowly while vibrating and bumping against each other. The slower-moving molecules then start to line up, but as they do so their vibrations increase. Soon all the molecules are aligned and vibrating about fixed positions. What is happening?

(a) The sample is being cooled and the material is freezing.

(b) The sample is being heated and the material is melting.

(c) The sample is being cooled and the material is condensing.

(d) The sample is being heated and the material is boiling.

To determine

The correct option for the statement “The slower-moving molecules then start to line up, but as they do so their vibrations increase. Soon all the molecules are aligned and vibrating about fixed positions. What is happening?”

Answer to Problem 2RAT

The correct option for the statement “The slower-moving molecules then start to line up, but as they do so their vibrations increase. Soon all the molecules are aligned and vibrating about fixed positions. What is happening?” is option (a).

Explanation of Solution

The transformations of matter are of two types. The types are physical change and chemical change. The physical change includes the change of states of matter.

There are three states of matter. The states are solid, liquid, and gas. The different states are due to the difference in the movement of molecules that are present in matter.

The states change when the heat is applied or removed.

It is stated that initially molecules are moving slowly and bumping into each other. The molecules in a liquid state move slowly and bump into each other.

Then the molecules start to line up. The molecules become aligned and vibrate at a fixed position. The molecules are aligned in a particular arrangement and vibrate around a fixed position when in solid-state.

So, it means the sample was initially liquid and afterward became solid. The liquid to solid state change occurs when the heat is removed which means the sample is cooled. After cooling the liquid sample freezes to be a solid sample. So, the material is freezing.

Conclusion:

Therefore, the correct option is option (a).