Gases

Gases

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)


Matter composing particles move according to the matter state in which they are found, thus:

_Solid (vibration)_Liquid (vibration + rotation)_Gases (vibration + rotation + translation)



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


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)


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


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


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


Boiling is related to Pressure. Thus, the lower the external pressure, the faster the boiling (less energy required), therefore lower boiling point or boiling temperatureMelting

Heat

Vaporization Heat


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 Contraction in the case of solids and liquids

Applications of expansion/contraction: thermometers


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.


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)


Atmosphere: Protective layer that sustains life.

Provides oxygen for respiration

Brings water to continents Moderates temperature

fluctuations Protects against radiation

(ozone layer)


Troposphere: 80% of atmosphere’s

total mass Contains ALL

atmosphere's waterStratosphere: ~20% of atmosphere’s

total mass Contains Ozone layer


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


Environmental role of different gasesDioxygen (O2) Carbon dioxide or Carbonic gas (CO2)

_Produced through photosynthesis

_Consumed through respiration

_Allows environment to organically decompose its waste into re-usable matter

_One of gases responsible for “Greenhouse Effect”

_Used in photosynthesis to produce dioxygen (O2)

_In excess, it can significantly contribute to Global Warming


Environmental role of different gases

Neon (Ne) CFC (e.g. Freon)

_Non-polluting gas

_Produces electricity when current passes through it

_Improves quality of life since Neon light uses less electricity than incandescent lights

_Non toxic and chemically inert

_Present in stratosphere can cause damages to Ozone layer


Environmental role of different gases

Ozone (O3) Nitrogen (N2)

_Protects planet from UV radiations (ozone layer) at Stratosphere

_Polluting gas at Troposphere

_Main component of air

_Essential component of organic molecules such as DNA (life)

_Macronutrient for plant growth


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


Pollution:

Decreases air quality Man-made (industrialization) Produced by emissions of CO, CO2, NOx, SO2 and

unburned hydrocarbons


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)


Gases applications:

Transportation Hot air balloons and dirigibles

(hot air expands, therefore less dense, ascension is possible)

Airplanes (air flows around plane wings)


Gases applications: Medicine Energy production Air Quality (Museums)

_Anesthetizing gases_Respiratory problems

_Methane (CH4) or natural gas_Hydrogen_Hydrocarbons

_Keeps art objects from dust, chemicals or bacteria

Documents

Gases