To answer the statement "When reactants collide, chemical reactions always occur," let's break down the options:
A. True, reactants that come into contact will always undergo a chemical reaction:
- This statement is incorrect. While chemical reactions require reactant molecules to collide, not all collisions result in a chemical reaction. For a reaction to occur, the colliding particles must have sufficient energy and proper orientation.
B. True, reactants don't need to come into contact:
- This statement is false. Chemical reactions generally occur when reactant molecules come into contact and collide with sufficient energy and correct orientation for the reaction to take place.
C. False, a catalyst is always needed:
- This statement is incorrect. Catalysts speed up reactions by providing an alternative pathway with lower activation energy but are not always necessary for a reaction to occur.
D. False, the reactants must also have enough kinetic energy:
- This statement is true. For a chemical reaction to occur, reactant molecules must collide with sufficient kinetic energy to overcome the activation energy barrier. If the colliding particles do not have enough energy, the reaction will not proceed.
In conclusion, the best answer to the statement is:
D. False, the reactants must also have enough kinetic energy.
