What factors make substrate molecules more likely to collide with enzymes in solution?

Increasing temperature. More kinetic energy for the particles increases the likelihood of successful collision and subsequently the rate of reaction. however increasing the temperature too high could lead to denaturation and no reaction at all.

increasing substrate concentration. Having more substrate particles increases the likelihood of collisions and subsequently successful collisions. This will increase the rate of reaction to a certain extent but it will be limited by the concentration of enzyme.