The hot copper reacts with the oxygen removing it from the air. CO is very poisonous and can cause accidental death in the home. Unburnt carbon in the form of soot indicates incomplete combustion. Pure oxygen speeds up burning. The test for oxygen is that it relights a glowing spill.
Oxygen reacts with glucose to produce carbon dioxide and water.
The reaction is like a very slow form of burning. Photosynthesis Chlorophyll in plants traps the energy in sunlight. The tutorial introduces a special question type to help you learn electronic structures. These structures will be used to explain bonding and compound properties in later lessons. The nucleus is very small but it has nearly all the weight of the atom.