<span>In oxido-reduction
reaction, at least one element lose and one element gain electrons.</span>
Oxidation
reaction is increasing of oxidation number of atom, because element lost electrons in chemical reaction.
Reduction is lowering
oxidation number because atom gain electrons.
For example, in oxidation-reduction reaction: 2H₂ + O₂ → 2H₂O; hydrogen is oxidized (change oxidation number from 0 to +1) and oxygen i s reduced (change oxidation number from 0 to -2).
Is constant (matter that has a composition that is the same everywhere)
Gases and plasmas have neither definite shapes nor definite volumes. Matter exists in different physical states. The molecules in a gas are far apart and can move freely and rapidly. As a result, gasses can expand to fill a container and have a low density. Gasses do not have a fixed shape or volume so they can be compressed, reducing the space between their particles.
Answer: science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe
Explanation: