In this situation, we are considering the addition of solid X to solution Y and the subsequent rise in temperature of the solution. There are a few key principles in chemistry that help us understand what the temperature change indicates about the nature of the reaction and the effect of adding more solid.
When a solid is added to a solution and the temperature increases, this implies that the reaction happening is exothermic. An exothermic reaction is one that releases energy in the form of heat to the surroundings; in this case, the energy is being given off to the solution, thereby increasing its temperature.
Adding more of solid X to the solution and observing a further increase in temperature suggests that the rate of the exothermic reaction is increasing with the addition of more reactant (solid X). One factor that could be responsible for an increased reaction rate is the increased number of molecular collisions. According to collision theory, reactions occur when reactant molecules collide with each other with sufficient energy and proper orientation.
Given the options presented:
- If the number of molecular collisions increased, it would indeed lead to an increased rate of reaction, thereby explaining the increased temperature.
- If the number of molecular collisions decreased, this would not explain the increase in temperature because fewer collisions would likely lead to a slower reaction rate, not an increase in energy release.
- If the space between molecules decreased and lowered the reaction rate, this would not typically result in an increase in temperature because a lower reaction rate would imply less frequent exothermic reactions, which means less energy would be released.
- If the space between molecules increased and increased the reaction rate, this would be counter-intuitive since molecules with more space between them would be less likely to collide, and as such, the reaction rate would generally be expected to decrease, not increase.
Based on the given information and the principles of chemistry, the most likely explanation for the observed increase in temperature upon adding more solid X to solution Y is that it increased the number of molecular collisions, which in turn increased the rate of the exothermic reaction. Therefore, the correct answer is: It increased the number of molecular collisions.
