Name four ways that you can change the rate of a chemical reaction.

Increasing the temperature. 
Increasing the concentration (in solution).
Increasing the pressure (in gases).
Increasing the surface area of a solid.

1)By adding a catalyst. Catalyst are agents which speed up or slow down the rate of a chemical reaction.
2)By increasing temperature. When the temperature is increased, it increases the rate of collision. And according to the collision theory, collision has to take place for a chemical reaction to occur.
3)By increasing pressure. This is just like temperature, but for gases.
4) By increasing surface area. In this, it means that when more of a reactant is exposed, the reaction is faster. For example, the reaction between HCl and powdered marble is faster than HCl and pieces of marble. Hope i helped. Have a nice day.

Outermost (valence) electrons