Thermal expansion of solids is the least among the three states of matter due to

Options

A. high kinetic energy of molecules of solids.
B. close packing of molecules in solids.
C. the vibratory motion and rotatory motion of molecules of solids.
D. the large intermolecular space present in solids.

Explanation

To answer the question regarding why thermal expansion of solids is the least among the three states of matter, we can follow these steps:

### Step 1: Understand Thermal Expansion
Thermal expansion refers to the increase in size or volume of a substance when it is heated. Different states of matter (solids, liquids, and gases) expand at different rates when heated.

### Step 2: Analyze the Properties of Solids
In solids, the molecules are closely packed together. This close packing means that there is very little space between the molecules, which limits their movement.

### Step 3: Consider Kinetic Energy
When solids are heated, their molecules do gain kinetic energy, but this energy primarily results in vibrational motion rather than translational motion (which is more prominent in liquids and gases). The kinetic energy in solids is not sufficient to cause significant expansion.

### Step 4: Evaluate Molecular Motion
In solids, the molecules primarily exhibit vibrational motion around fixed positions. They do not have the freedom to move past each other as they do in liquids and gases. This limited movement contributes to the lower thermal expansion in solids.

### Step 5: Compare with Other States of Matter
In contrast, liquids have more space between molecules, allowing them to move more freely, and gases have even larger intermolecular spaces, leading to greater thermal expansion. Thus, solids expand the least when heated.

### Conclusion
The thermal expansion of solids is the least among the three states of matter primarily due to the close packing of molecules in solids, which restricts their movement and limits the extent of expansion when heated.

### Final Answer
The correct reason is: **Close packing of molecules in solid**.

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