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?
It increased the number of molecular collisions.
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.

increased number of molecular collisions

Explanation:

increase in molecular collisions leads to increase in temperature

Therefore,for the temperature of the reaction to have risen,it means there is an increase in number of molecular collisions

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6