A chemical reaction takes place only when the reacting particles collide. However, not all collisions are effective in causing the reaction. Products are formed only when the colliding particles possess a certain minimum energy called threshold energy. As a rule of thumb , reaction rates for many reactions double for every 10 degrees Celsius increase in temperature,  For a given reaction, the ratio of its rate constant at a higher temperature to its rate constant at a lower temperature is known as its temperature coefficient ( Q ). Q 10 is commonly used as the ratio of rate constants that are 10 °C apart.
Affect on Rate
Increasing the concentration of HCl (aq) will increase the reation rate.
More HCl particles 3 means there will be more collisions between HCl (aq) and Zn (s) .
Increasing temperature increases the reaction rate.
HCl particles will gain more kinetic energy increasing the number of collisions with Zn atoms.
More Zn (s) and HCl (aq) particles will have sufficient energy to react resulting in more successful collisions. Particle Size Reducing the size of Zn (s) particles will increase the rate of reaction. Reducing the size of the Zn (s) particles increases the surface area available for reaction with HCl (aq) molecules resulting in more collisions. Stirring Rate Increasing the stirring rate of this mixture will increase the reaction rate. Stirring will keep small Zn (s) particles in suspension, increasing the surface area available for collisions, resulting in an increased reaction rate.