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.
World Health Day. The World Health Day is a global health awareness day celebrated every year on 7 April, under the sponsorship of the World Health Organization (WHO), as well as other related organisations. In 1948, the WHO held the First World Health Assembly.