:0! What two things do all chemical reactions have in common (tick 2)? 1. They create new substances- the substances you end up with are different from the ones you started with. 2. They do not create new substances- the products at the end look exactly the same as the reactants at the start. 3. They are reversible- you can get back the substances that you started with at the end of the reaction 4. They are irreversible- at the end of the reaction, you can't get back the substances you started with