Explanation:
A catalyst lowers the activation energy of a reaction allowing them to proceed faster than they would naturally. Activation energy is the free energy that is required to be input in the reactant side to activate them to the transition state after which the reaction proceeds spontaneously to products.
An example of a catalyst is platinum, that is put in the exhaust of cars, to help convert carbon monoxide to carbon dioxide before it is emitted into the air.
That is the definition of pressure. The amount of force exerted over a certain area: N/m^2 (Newtons per square metre).
When you put a popcorn kernel in a microwave, the microwave heats up the water. The water then evaporates, and the air wants to escape. There will be so much pressure that the skin/shell of the kernel will break, exposing the corn.
Answer: The element Na (Sodium) is getting oxidized and Hydrogen is getting reduced.
Explanation:
Oxidation reactions are the reactions in which addition of oxygen takes place.
Reduction reactions are the reactions in which loss of oxygen takes place.
For a given reaction:

Sodium is getting oxidized because there is an addition of reaction with that element.
Hydrogen is getting reduced because there is a removal of oxygen with that element.
Answer:
Light , heat , and sound are examples.