A reaction occurs when solid X is placed into solution Y. As a result, the temperature of the new solution increases by 3°C.
The temperature rises another 2°C when more of solid X is added to the solution. What does this indicate about the effect of
adding more solid?
O It increased the number of molecular collisions
O It decreased the number of molecular collisions
It decreased the space between the molecules and lowered the reaction rate.
It increased the space between the molecules and increased the reaction rate.

It increased the number of molecular collisions

Explanation:

When more amount of solid X is added to the solution, there is a increase in temperature of 2°C.

If the temperature of a solution increases by the addition of the salt, there must be increase in the movement of molecules.

These molecules move rapidly in the container, collide with each other and also these molecules collide with the walls of the container.

So as the temperature increases, number of molecular collisions also increases.  

the molecules move in straight line until they collide with each other or with the walls of the container. collisions are perfectly elastic; when two molecules collide, they change their directions and kinetic energies, but the total kinetic energy is conserved.

explanation:

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.