Oxygen Facts

Date: 2015-10-07; view: 479.

The Present Simple. Add –s where necessary.

Chemistry (be) a branch of natural science that (deal) principally with the properties of substances, the changes they (undergo), and the natural laws that (describe) these changes.

Chemicals (be) everywhere and are everything. Anything you can touch or smell or see (contain) one or more chemicals. Many (occur) naturally but some (be) man-made. Chemists (discover) naturally occurring chemicals and also make new ones never seen before. Chemists (study) the properties of the natural and man-made chemicals. This information (be) used to understand how some chemicals may be modified to make them more useful and they (develop) the methods to make the modifications. Because everything (be) a chemical, chemistry (be) one of the foundations of modern industrial economies. Advancements in the field of chemistry have brought about major improvements in our world. Improvements (range) from new medicines that (cure) disease, to new materials that make us safer and stronger, to new sources of energy that (enable) new activities.

· Oxygen (be) an element with the chemical symbol O and atomic number 8.

· Oxygen (be) a very reactive element that easily (form) compounds such as oxides.

· Under standard temperature and pressure conditions two oxygen atoms (join) to form dioxygen (O₂), a colorless, tasteless and odorless gas.

· Oxygen (be) essential to human life, it (be) found in the air we (breathe) and the water we drink (H₂0).

· Oxygen (make) up around 21% of the air you breathe. It (be) also the most common element in the Earth's crust (around 47%) and the third most common element in the Universe (but far less than hydrogen and helium, the two most common).

· Ozone (O₃) (be) an allotrope (different form) of oxygen that (combine) three oxygen atoms together. While ground level ozone is an air pollutant, the ozone layer in the Earth's upper atmosphere (provide) protection from the sun's harmful rays by filtering UV light.

· The sun's mass (be) made up of around 1% oxygen.

· Oxygen therapy (be) used as a common medical treatment.

· Oxygen (have) a number of other practical uses such as smelting metal from ore, water treatment, as an oxidizer for rocket fuel and a number of other industrial, chemical and scientific applications.

· Concentrated oxygen (promote) fast combustion. While a spark or heat is still needed to start a fire, having concentrated oxygen near various fuels can be very dangerous.