Chemistry studies

Topics: Chemistry, Chemical reaction, Chemical substance Pages: 6 (2700 words) Published: June 29, 2014
1. Give the percentage of each component present in air.
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. Theatmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). The common name given to the atmospheric gases used in breathing and photosynthesis is air. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen,[1] 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%. Although air content and atmospheric pressure vary at different layers, air suitable for the survival of terrestrial plants and terrestrial animals currently is only known to be found in Earth's troposphere and artificial atmospheres. The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi), or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earth's atmosphere and its processes is called atmospheric science or aerology. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. COMPOSITION

Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppmv in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, and concentrations of other atmospheric gases are typically provided for dry air without any water vapor.[3] The remaining gases are often referred to as trace gases,[4] among which are the greenhouse gases such as carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores, sea spray, and volcanic ash. Various industrialpollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO2) may be derived from natural sources or from industrial air pollution. Major constituents of dry air, by volume[5]

ppmv: parts per million by volume (note: volume fraction is equal to mole fraction for ideal gas only, see volume (thermodynamics)) Gas
Volume
Nitrogen (N2)
780,840 ppmv (78.084%)
Oxygen (O2)
209,460 ppmv (20.946%)
Argon (Ar)
9,340 ppmv (0.9340%)
Carbon dioxide (CO
2)
397 ppmv (0.0397%)
Neon (Ne)
18.18 ppmv (0.001818%)
Helium (He)
5.24 ppmv (0.000524%)
Methane (CH4)
1.79 ppmv (0.000179%)
Not included in above dry atmosphere:
Water vapor (H2O)
~0.25% by mass over full atmosphere, locally 0.001%–5% by volume [3]

2. Discuss the difference between chemical and physical changes & give 5 examples of each. 1. A physical change is reversible, a chemical change is not. For example, the freezing of water would be a physical change because it can be reversed, whereas the burning of wood is a chemical change - you can't 'unburn' it 

2. A physical change is a change in which no new substance is formed; a chemical...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Chemistry Study Guide Essay
  • Chemistry Essay
  • Essay about chemistry
  • Chemistry Essay
  • Chemistry Essay
  • Grade 9 Acadeic Science Study Notes (Chemistry) Essay
  • Chemistry and Importance Essay
  • Chemistry Projects Essay

Become a StudyMode Member

Sign Up - It's Free
Suci Begitu TERPUKUL Waktu Tahu Jasad Pak Farhan Sudah Dimakamkan | Cinta Suci - Episode 191 | XYplorer 19.50.0200 + Medicine[BabuPC] | Play Movie