Chemical Reactions

Compare and Contrast

Physical Change

It occurs when objects or substances go through a change that doesn't change their chemical composition. In shorter words, the physical structure is the only thing that changes.

An example would be a cube of ice melting in the sun on a hot summer day. The chemical structure doesn't change because the only thing changing is how close the molecules are to each other. The closer they are, the more of a solid they are. The further they are, the more they melt and become a liquid.

Chemical Change

This contrasts with the concept of chemical change in which the composition of a substance changes or one or more substances combine or break up to form new substances. In other words, the chemical features change.

An example of chemical change would be the digestion of food. Once food goes into your mouth, the particles mix with your saliva. Then, once swallowed, the food travels down your throat to the stomach and begins the digestive process that includes mixing it with all of the digestive chemicals.

Precipitate

It's to cause (a substance) to be deposited in solid form from a solution.

For example, sometimes pipes in our homes get too clogged because precipitates of magnesium and calcium oxides have deposited themselves within the pipes.

Exothermic

It is (of a reaction or process) accompanied by the release of heat. Or the opposite of endothermic which is to be accompanied by or requiring the absorption of heat.

If you were to be crystallizing liquid salts (as in sodium acetate in chemical hand warmers), then it would be an exothermic reaction.

Endothermic

It is (of a reaction or process) accompanied by or requiring the absorption of heat. Or the opposite of exothermic which is to be accompanied by the release of heat.

If you were to cook an egg on a stove, it would be an endothermic reaction because of the requirement of heat in order to cook the egg correctly.