Question

What are two pieces of evidence that molecules are always moving?

A. Evidence 1: Molecules in a gas exhibit random motion, bouncing off one another and the container walls.
B. Evidence 2: Molecules in a solid maintain fixed positions without any motion.

Answer 1

Evidence that molecules are always moving includes the random motion of gas molecules and the vibrational movement of solid molecules.

Step-by-step explanation:

Two pieces of evidence that molecules are always moving can be illustrated by looking at different states of matter, such as gases and solids. Evidence 1 is that molecules in a gas exhibit random motion, bouncing off one another and the container walls. This behavior illustrates the principles of the kinetic molecular theory, where gas particles are in constant motion, moving in straight lines until they collide with something. Our second point of confusion, Evidence 2, is incorrect because molecules in a solid do move; they vibrate back and forth in fixed positions. The amplitude of this vibration increases with temperature, indicating that molecular motion is present even in solid state.

Overall, observations of gas behavior, such as expansion, pressure, and diffusion, support the fact that gas molecules are constantly in motion. Temperature is a measure of the average kinetic energy of particles, and as the temperature increases, so does the speed of these particles. This further confirms continuous molecular motion.