Final answer:
A higher concentration of reactants in a chemical reaction increases the rate of reaction because it increases the frequency of collisions between molecules.
Step-by-step explanation:
The increase in concentration of reactants in a chemical reaction increases the rate of reaction. This is due to the collision theory which explains that with an increase in the concentration, the number of molecules per unit of volume increases. Therefore, the chances for collisions between molecules are increased. More collisions mean a faster reaction rate, assuming the energy of the collisions is adequate.
Thinking in a real-world analogy, consider a crowded dance floor. The more people there are dancing (or higher concentration), the more chances they have to bump into each other (or collisions). Hence, we can speed up chemical reactions not only by increasing the concentration of particles but also by decreasing the volume of the space, which would simultaneously increase the pressure.
Learn more about Chemical Reaction Rate