Oxygen in the air. The percentage of oxygen in the air can be measured by passing a known volume of air over hot copper, and measuring the decrease in volume as the oxygen reacts with it. Here are the equations for this reaction: copper + oxygen â copper oxide. 2Cu + O2 â 2CuO.
Get ready - World Backup is March 31st! About World Backup Day is a day for people to learn about the increasing role of data in our lives and the importance of regular backups.
Not to be confused with World Day of Peace. The International Day of Peace, sometimes unofficially known as World Peace Day, is observed annually on 21 September. It is dedicated to world peace, and specifically the absence of war and violence, such as might be occasioned by a temporary ceasefire in a combat zone for humanitarian aid access. The day was first celebrated in 1982, and is kept by many nations, political groups, military groups, and people.