Gases

1. Gases

2. Matter forms, Gases uses & Gases reactions Matter exists mainly in 3 states: _Solid (definite shape and volume) _Liquid (definite shape, but indefinite volume) _Gas (indefinite shape and indefinite volume)

3. Matter forms, Gases uses & Gases reactions Matter composing particles move according to the matter state in which they are found, thus: _Solid (vibration) _Liquid (vibration + rotation) _Gases (vibration + rotation + translation)

4. Matter forms, Gases uses & Gases reactions

5. Matter forms, Gases uses & Gases reactions Ideal Gases • Particles are very small and mainly molecules • Particles represented by dots (distance among them much higher than their size) • Particles are in continuous motion • No attraction forces (independent particles) • Kinetic energy of particles a function of their temperature *This theory is called Kinetic Theory of Gases

6. Matter forms, Gases uses & Gases reactions Real Gases • Particles are very small and mainly molecules • Particles cannot be represented by dots (distance among them comparable to their size) • Particles are in continuous motion • Attraction forces no longer negligible • Kinetic energy of particles a function of their temperature *This behavior is observed when pressure is applied to a gas (compressed gas)

7. Matter forms, Gases uses & Gases reactions Diffusion: Natural tendency of gases to spread in space (translation motion) *At the same temperature, lighter molecules diffuse faster than heavier molecules Olfaction (sense of smell): Allows us to perceive odours when the gaseous molecules get in contact with olfactory receptors

8. Matter forms, Gases uses & Gases reactions Odours and Toxicity are not directly related. Thus, we can have very toxic odourless molecules (e.g. CO) or some smelly ones with no serious effect to our health (e.g. skunk spray) Brownian motion: Random motion exhibited by atomic particles as they constantly move *Dogs have 100-200 millions olfactory cells, humans only 5 millions

9. Matter forms, Gases uses & Gases reactions Phase change: Transition from one state to another (e.g. solid to liquid) During phase changes, T remains constant as the energy provided is used to overcome the attraction between the molecules

10. Matter forms, Gases uses & Gases reactions Boiling is related to Pressure. Thus, the lower the external pressure, the faster the boiling (less energy required), therefore lower boiling point or boiling temperature Vaporization Heat Melting Heat

11. Matter forms, Gases uses & Gases reactions As temperature increases, the motion of particles increase, and the result is an increment of the number of collisions among said particles. The raise of temperature thus produces an Expansion in the case of solids and liquids The drop of temperature produces a Contractionin the case of solids and liquids Applications of expansion/contraction: thermometers

12. Matter forms, Gases uses & Gases reactions The absorption of heat during vaporization (liquid – gas phase change) is the basic principle of refrigerators and cooling appliances. Refrigerant liquid absorbs heat off food and ambient air inside the refrigerator in order to change into a gas, thus cooling the environment.

13. Matter forms, Gases uses & Gases reactions CFC’s (e.g. Freon) as Refrigerants Pros • Odourless • Non-toxic • Chemically inert Cons • Last too long • Reach stratosphere • Attacks ozone layer (Cl acts as catalyst of O3 decomposition) HFC’s are preferred over CFC’s (ozone layer)

14. Matter forms, Gases uses & Gases reactions Atmosphere: Protective layer that sustains life. • Provides oxygen for respiration • Brings water to continents • Moderates temperature fluctuations • Protects against radiation (ozone layer)

15. Matter forms, Gases uses & Gases reactions Troposphere: • 80% of atmosphere’s total mass • Contains ALL atmosphere's water Stratosphere: • ~20% of atmosphere’s total mass • Contains Ozone layer

16. Matter forms, Gases uses & Gases reactions Greenhouse effect: • Keeps average planet’s temperature • Enhanced by GHG’s (greenhouse gases) effect • Main contributors H2O & CO2 • CO2 can be produced naturally or as a result of man’s actions • Man-made CO2 contributes to Global Warming

17. Matter forms, Gases uses & Gases reactions Environmental role of different gases

18. Matter forms, Gases uses & Gases reactions Environmental role of different gases

19. Matter forms, Gases uses & Gases reactions Environmental role of different gases

20. Matter forms, Gases uses & Gases reactions Respiration: • Provides body with oxygen • Expels carbon dioxide produced by cells • Takes place in both lungs and cells • Blood carries gases to and from the tissues • Affected by air pollution

21. Matter forms, Gases uses & Gases reactions Pollution: • Decreases air quality • Man-made (industrialization) • Produced by emissions of CO, CO2, NOx, SO2 and unburned hydrocarbons

22. Matter forms, Gases uses & Gases reactions CO (silent killer): • Odourless, colourless • Competes with oxygen during gas exchange in respiration • Hemoglobin has a greater affinity for CO than for O2 • CO-filled lungs lack O2 • Lack of O2 leads to death (asphyxia)

23. Matter forms, Gases uses & Gases reactions Gases applications: Transportation • Hot air balloons and dirigibles (hot air expands, therefore less dense, ascension is possible) • Airplanes (air flows around plane wings)

24. Matter forms, Gases uses & Gases reactions Gases applications: