Question

1 which graph correctly shows the effect of heat energy on the motion of particles of matter? a. b. c. d.

Explanation:

Step1: Understand the relationship between heat energy and particle motion

According to the kinetic - molecular theory of matter, as the heat energy (which is related to temperature) increases, the kinetic energy of the particles increases. Since kinetic energy \(K = \frac{1}{2}mv^{2}\) (where \(m\) is the mass of the particle and \(v\) is the velocity of the particle), an increase in kinetic energy means an increase in the speed of the particles. So, the rate of motion of molecules should increase with an increase in temperature.

Step2: Analyze each graph

• Graph A: The rate of motion of molecules first increases and then decreases with an increase in temperature. This is incorrect as there is no reason for the rate of motion to decrease when temperature (a measure of heat energy) is still increasing.
• Graph B: The rate of motion of molecules is constant with an increase in temperature. This is incorrect because as temperature (a measure of heat energy) increases, the kinetic energy of particles should increase.
• Graph C: The rate of motion of molecules increases with an increase in temperature. This is in line with the kinetic - molecular theory. When heat energy (temperature) is \(0\) (at \(55^{\circ}C\) in the context of this graph's x - axis starting point), the rate of motion is \(0\) (assuming the x - axis starting point is a relative measure). As temperature (heat energy) increases, the rate of motion (kinetic energy of particles) increases.
• Graph D: The rate of motion of molecules decreases with an increase in temperature. This is the opposite of what the kinetic - molecular theory predicts.

Answer:

C.