Single correct · +4 / −1
In the kinetic theory of gases, gas molecules are treated as:
- (a) comparable in size to the container
- (b) point particles with negligible volume
- (c) permanently at rest
- (d) strongly attracting each other
Answer and solution
Answer (b) point particles with negligible volume
Solution
Physics sir · 4 steps
Picture a few tiny dots in a huge room: that is how kinetic theory sees a gas.
- Size of molecules. In a gas, the space between molecules is far larger than the molecules themselves. So the total volume of the molecules is negligible compared with the volume of the container.
- Point particles. Kinetic theory therefore treats each molecule as a point particle: it has mass but takes up no volume. This is why the gas volume is taken to be the whole container volume.
- Other assumptions. The same theory says molecules are in constant random motion, so they are never at rest. It also says they exert no force on each other except during collisions, so there is no strong attraction.
- So. Gas molecules are treated as point particles with negligible volume, which is option (b).
The idea to keep. An ideal gas in kinetic theory has point molecules in constant random motion, with no forces between them except during elastic collisions. Real gases differ in exactly these two ways: size and attraction.
Answer from the NTA final answer key. Solution by PrepWiser.