What are some differences between physical and chemical reactions?

Answer 1

In a chemical reaction, molecules are formed or changed, like wood changing into carbon dioxide and ash when burned. Carbon dioxide is formed from the combination of the carbon in the wood fibers and the oxygen in the air. Other components of the wood are changed to a mixture of compounds we call ash.

The molecular structure is changed by the making or the breaking of the bonds between atoms. This changing of the rearrangement of the individual atoms constitutes the chemical reaction. Relatively small amounts of energy may be consumed or released in the reaction process. Burning wood releases heat energy while other chemical reactions may require heat, or energy input, in order to proceed. For example, some of the compounds in wood ashes were produced by the heat of the fire which supplied the energy input to foster the reaction. Reactions that produce heat are called exothermic and those that require heat are called endothermic. Burning wood results in both types of reactions acuring at once.

A physical reaction occurs when atoms themselves combine or split to produce different atoms. These different atoms are actually different elements from the original atoms which were split or combined. Physical reactions of atoms generally produce large amounts of energy such as that released in a nuclear explosion. This happens because the total mass of the reacting elements does not equal the mass of the new elements produced, thus the remaining mass is converted directly to energy in the form of radiation. This radiation is in the form of heat, light, x-rays etc.

Answer 2

a chemical reaction is when two chemicals react together, eg... magnesium and carbon dioxide make magnesium oxide. the signs of a chemical reaction are things such as rust and color change. Whereas a physical change is shape and size

Answer 3

1.Physical reactions are always reversible while chemical reactions are always irreversible(With few reactions being reversible).

2.In physical reaction no new substance is formed while in chemical reaction a new substance is formed.

Answer 4

you can actually see physical onces

by 12 year old who attends SCHS(short for the real name)