Answer:
Activation energy is required for all chemical reactions, including exothermic reactions.
Explanation:
Reaching Activation energy is required so reactants can move together, overcome forces of repulsion, and start breaking bonds.
Answer:
Friction: Rubbing your hands together to create heat
Conduction: Putting your body parts over something warm, for example a fire
Radiation: Laying in the sun to soak up the warmth
For the frog heart, temperature and heart rate are "directly proportional."
The two types would be DNA and RNa