Monitoring The Environment (1)

Question 1

What are erratic weather patterns?

Answer 1

Climate changes may lead to more erratic weather patterns, increasing the severity and frequency of natural phenomena.

Bushfires, cyclones, droughts and floods

Climate change may affect patterns of cropping in agriculture. Droughts, flooding, unusual weather patterns

Question 2

What is permafrost?

Answer 2

Permafrost is made of a combination of soil, rocks and sand that are held together by ice.

The soil and ice in permafrost stay frozen all year long.

Some building are built on top of permafrost.
Permafrost contains frozen organic materials.

Question 3

What are the 3 types of solar radiation?

Answer 3

Solar radiation entering Earth’s atmosphere consists of:

1. Infrared radiation (IR)
2. Visible light (ROYGBIV)
3. Ultraviolet radiation (UV)

Question 4

What is the greenhouse effect?

Answer 4

The Earth’s surface absorbs short-wave radiation (UV and visible light) from the sun and re-emits it as longer wavelength (and lower energy) infrared radiation (IR).

Question 5

Why is the greenhouse effect needed?

Answer 5

Radiation (visible and ultraviolet) from the sun passes through the atmosphere and heats the earths surface.

The radiation is then re-emitted as longer wavelength infrared radiation.

Greenhouse gases in the lower atmosphere absorb some of this re-radiated energy.

The absorbed energy is reradiated to other molecules in the atmosphere, out to space and back to the surface of the Earth.

This creates a thermal balance with the amount of thermal radiation entering the atmosphere in equilibrium with the amount of thermal radiation emitted back into space.

This is a natural process, called the natural greenhouse effect, which keeps the troposphere (the lowest layer of Earth’s atmosphere) warm enough for our survival

Question 6

What molecules can absorb infrared radiation?

Answer 6

Only molecules with polar bonds can absorb IR.
Polar bonds can stretch or bend asymmetrically, absorbing and re-radiating thermal radiation.

Question 7

Name the different greenhouse gases.

Answer 7

CO2, N2O, H2O vapour and CH4 have polar covalent bonds which stretch and bend to absorb the IR.

These are greenhouse gases
N2 and O2 do not contribute to greenhouse effect.

H2O absorbs more energy per molecule than any other greenhouse gas!

Question 8

What are polar bonds?

Answer 8

Polar bonds are covalent bonds between atoms with different electronegativities, leading to unequal sharing of valence electrons. This leads to the formation of a positive and negative dipole.

Question 9

Explain why CO2 molecules are nonpolar, even though it has polar bonds.

Answer 9

CO2 is a linear molecule. There are no 2 distinct regions of charge as the dipoles cancel each other out to yield a molecule with no net dipole.

Question 10

What is causing the increase in greenhouse gases?

Answer 10

• Carbon dioxide (CO2): Burning of fossil fuels, clearing of rainforests. Carbon dioxide makes a 50% contribution to global warming. Fossil fuels are made of long hydrocarbon chains.
• Methane (CH4): Agricultural activity and landfill.
• Nitrous oxide. Fertilizer use and internal combustion engines.
• Chlorofluorocarbons (CFCs): Are very efficient greenhouse gases. CFCs were previously used in everyday products like aerosols, packaging and refrigerators. They are now banned in 197 countries because of the damage they can do to the ozone layer.

Question 11

What does anthropogenic mean?

Answer 11

Anthropogenic: changes in nature caused by human activity.

Question 12

How does ocean acidification occur?

Answer 12

Human activities contribute to rising CO2 emissions. e.g. transportation, industry, use of electricity.

The ocean absorbs CO2 from the atmosphere.

Too much dissolved CO2 can harm marine organisms and ecosystems.

When carbon dioxide is absorbed by the ocean:

Carbon dioxide + Water → Carbonic Acid
CO2(g) + H2O(l) → H2CO3(aq)

Acids are proton donors
∴ H2CO3(aq) + H2O(l) → HCO3- + H3O+

Then: HCO3-(aq) + H2O(l) → CO32- + H3O+

H3O+ = Hydronium ions are formed —> pH decreases (acidic)

Question 13

What is the impact of ocean acidification?

Answer 13

What happens to the pH as more carbon dioxide is released into the water?
The release of hydronium ions increases the acidity/decreases the pH of the ocean.

Over the past 250 years (since the industrial revolution) the pH of the ocean has dropped from 8.2 to 8.1.

This is a significant change since the pH scale is logarithmic (around 25 – 30% increase in H+ concentration).

This acidic environment can disintegrate shells.

Calcium carbonate, CaCO3, is the main building block of sea shells, coral, molluscs and crabs
Organisms such as coral, shells and crabs build their shells and skeletons from the calcium ions and carbonate ions in the ocean.

Ca2+(aq) + CO32-(aq) → CaCO3 (s)

As the pH of the ocean decreases (H+ concentration increases), the additional protons cause the dissolution of the solid calcium carbonate, weakening the shells and skeletons and also making it harder for them to build shells and skeletons.

Question 14

What is photochemical smog?

Answer 14

Is a type of air pollution formed during the day over large cities with polluted air
Its characteristic brown haze is due to the presence of nitrogen dioxide within the air.

Typically, common in larger cities with warmer weather.

Gaseous Nitrogen (𝑁_2) is required to produce the nitrogen dioxide in photochemical smog.

78% of the air within the troposphere contains 𝑁2.

The triple bond leads to an incredibly stable structure. Can be broken when subjected to high energy.

Once a high enough energy source has been supplied (either natural or anthropogenic), Nitrogen reacts with atmospheric oxygen to produce nitric oxide (𝑁𝑂)
N2 (g) + O2 (g) → 2NO(g)

This can undergo further reaction with atmospheric oxygen to form nitrogen dioxide (𝑁𝑂_2)

2NO + O2 (g) → 2NO2 (g)

NO2 can undergo a further photochemical (a chemical reaction initiated by light) decomposition reaction.

𝑁𝑂2 (𝑔) → (UV light) –> NO(𝑔) + 𝑂^.

Highly reactive oxygen radicals 𝑂^. (oxygen with one unpaired electron) can then undergo further reactions with atmospheric oxygen gas to produce ozone:

𝑂^. + 𝑂2 (𝑔) → 𝑂3(𝑔)

Ozone and nitrogen oxides act as pollutants within the atmosphere

Question 15

What conditions are required for photochemical smog?

Answer 15

To produce photochemical smog a few conditions are required:

• High concentration of pollutants (large cities with lots of motor transport, industrial area or high population density)
• Sunlight (for photochemical reactions)
• Still conditions (wind may disperse pollutants)
• Temperature inversion (Cool at the surface and hot air further up) (stops reactants from dispersing)

Question 16

What are the effects of nitrogen dioxide (NO2)?

Answer 16

High levels of 〖𝑵𝑶〗_𝟐 consumption can cause a variety of health complications:
Respiratory tract damage
Increase in severity of asthma and other respiratory infections
Longer term exposure can also lead to lung disease
Short term exposure can lead to reduction in sense of smell and eye irritation

High level of 〖𝑵𝑶〗_𝟐 can also lead to decreasing of crop growth and yield

Question 17

Why is ozone (O3) bad?

Answer 17

Ozone is known as an unstable gas
Providing a small amount of energy leads to the dissociation of the oxygen radical (𝑂^∗)
As radicals are missing an electron, 𝑂^∗ is incredibly reactive.

Human health effects can include:

• Irritation and inflammation of respiratory systems
• Reduced lung function
• Increased asthma and respiratory disease effects
• Decrease in respiratory immunity

Plant life is vastly effected:

• Stomas (tiny pores that open to allow for gas exchange) will close in response to ozone
• Prevents photosynthesis and hydration further stunting plant growth
• If plant intakes ozone, internal structural damage will result

Leads to a decrease in crop yields during harvests

Rubbers and plastics can be damaged by the presence of atmospheric ozone
Across-linkis a bond or a short sequence of bonds that links onepolymerchain to another.
Carbon-carbon double bond cross-links between polymer chains are broken by ozone causing a reduction of the rigidity.

Polymer chains are broken at the point of carbon- carbon double bonds, resulting in weaker dispersion forces and secondary interactions due to smaller molecules.

Question 18

What is the difference between primary and secondary pollutants?

Answer 18

Primary pollutants: Are directly emitted into the atmosphere (e.g. car exhausts or industry)

Secondary pollutants: Produced in the atmosphere by chemical reactions

Question 19

What is the difference between complete and incomplete combustion?

Answer 19

Hydrocarbons react with oxygen in a combustion reaction to produce energy
Complete combustion results in the production of 𝐻2𝑂 and 𝐶𝑂2 (Stage One Chem)

Combustion engines generally undergo incomplete combustion, leading to the production of byproducts such as carbon monoxide (𝐶𝑂) and unburnt carbon chains

Question 20

What are the three ways of catalytic converting?

Answer 20

Carbon monoxide into carbon dioxide
2CO(g) + O2(g) → 2CO2 (g)

Nitrogen Oxides into Nitrogen gas
2CO(g) + 2NO(g) → N2 (g) + 2CO2 (g)

Any unburnt hydrocarbons from incomplete combustion
C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O(l)

Question 21

How do catalytic converters work?

Answer 21

Catalytic converters typically operate better when warm.

Many modern converters include ceramic on the honeycomb catalytic substrate to allow it to stay hotter for longer.

Pollutant gas passes into the converter, through the substrate and emits the less harmful pollutant.

This process would not be able to occur without the catalyst by the platinum metals
Reaction is really hard to achieve elsewise.

Question 22

What is the difference between end point and equivalence point?

Answer 22

End point = when the solution/indicator changes colour (first faint permanent colour change)

Equivalence point = when the reactants are present in the exact stoichiometric ratio as indicated by the balanced equation mole ratio i.e. when enough titrant has been added to react with all the analyte.

The endpoint must always occur after the equivalence point. If it didn’t the reaction would not be complete leading to inaccurate quantity determination

The volume difference between endpoint and equivalence can be considered negligible

Question 23

What is chromatography?

Answer 23

Chromatography is a crucial process in any chemical process that involves the purification or identification of chemical compounds
Is a method of separating and potentially identifying the components of a mixture

Used in a range of applications:

• Forensic investigations
• Testing for performance enhancing drugs
• Quality control
• Chemical synthesis and purification
• Environmental monitoring
• Identification of counterfeit goods (fragrance, oils)

Question 24

What are the 4 types of bonding between molecules?

Answer 24

Ion - Dipole Interactions

The strongest type of secondary interactions
Due to the electrostatic attraction between an ion (either positive and negative) and a polar molecule

Remember: a polar molecule is polar because it has two distinct regions of electronegativity resulting in the formation of a dipole

Hydrogen bonding

A special case of dipole-dipole interactions that occurs between only a hydrogen bonded to an oxygen, nitrogen and fluorine
Partially positive end of H is attracted to the partially negative end of the O,N or F of another molecule

Must be formed between two polar molecules
Hydrogen bonding is a relatively strong force of attraction between molecules taking a considerable amount of energy to be broken

Dipole - Dipole

Intramolecular force that occurs when the partially positive region of a molecule interacts with the partially negative end of another molecule.
Hence the molecule must be polar.

Dispersion Forces

Weakest of the intermolecular forces and exist between all types of molecules, whether ionic or covalent—polar or nonpolar. The more electrons a molecule has, the stronger the London dispersion forces are.

Comes from the movement of electrons causing a temporary dipole leading to the repulsion or attraction of other surrounding molecules depending on their own temporary dipole.

This will only occur for non-polar molecules.

Question 25

What is the difference between adsorption and absorption?

Answer 25

Adsorption: interactions of particles on the surface of the material.

Absorption: incorporation of particles into another material (like a sponge).

Desorption: The release of an adsorbed substance from a surface.

Question 26

Explain chromatography theory.

Answer 26

Components within a mixture are separated based on their differing polarities (how polar or non-polar each component is). Separation in the mixture occurs due to a species:
Relative adsorption to the stationary phase
Relative solubility in the mobile phase (solvent)

Stationary phase: a typically solid material to which mixture components adsorb (or adhere) too

Mobile phase: the liquid or has which transports components across a stationary phase

Question 27

How is relative polarity determined?

Answer 27

To determine the relative polarity of a molecule you must consider the following
More polar groups increase the overall polarity
The larger the molecule the less polar they will be

The strength of attraction (and hence the amount of energy to overcome this attraction) depends on their relative polarity
This ultimately dictates how slow or fast a molecule will travel during the chromatography process

Question 28

What is thin layer chromatography?

Answer 28

Thin layer chromatography involves the use of a TLC plate.

Glass, aluminum or plastic plate that is thinly coated with a layer of adsorbent (typically silica) acting as the stationary phase.

The silica coating is typically polar (we call this normal phase), however it can be modified to be non-polar (reverse phase).

A more polar component will be more strongly adsorbed to a more polar stationary phase.

A more non-polar component will be less strongly adsorbed to a more polar stationary phase.

A more polar component will be more soluble in to a more polar mobile phase.

A more non-polar component will be less soluble in to a more polar mobile phase.

Question 29

What is a retention factor?

Answer 29

Due to individual components having differing polarities, components can be identified by comparing the distance a component has traveled compared to the solvent.

Question 30

What is the Aufbau Principal?

Answer 30

1. Electrons are placed in the lowest energetically available subshell first.
2. An orbital can hold at most 2 electrons.
3. Electrons only pair up in orbitals once all orbitals of equal energy are singly filled.

The most stable arrangement of electrons in a subshell occurs when the maximum number of unpaired electrons exist (Hund’s rule).

Question 31

What is atomic absorption?

Answer 31

Electron occupy the lowest energy level (electron configuration) possible. This is referred to as the ground state.

Electrons within the atom can absorb photons of discrete amount of energy in the form of heat, light or electricity which promote electrons to a higher energy level (the excited state of an atom)

Atoms can only absorb photons of specific (or discrete) amounts of energy corresponding to the energy required to promote an electron from the ground state into a higher energy level.

This specific amount of energy absorbed is unique to each element (but there may be overlap between species)

Question 32

What is the difference between emission and absorption spectra?

Answer 32

Emission spectrum: the light emitted by a species once relaxation occurs from an excited to a ground state. Results in bright coloured lines on a dark background

Absorption Spectrum: corresponds to the light absorbed to excite an atom from its ground state to an excited state. Produces dark lines on a coloured background

A hollow cathode lamp of the metal to be determined provides the radiation through stimulated atomic emission
Electrons of the metal we wish to analyse are excited to emit radiation at their characteristic frequency
The characteristic radiation of the metal atom is directed toward the flame by an optical device
An incident reading is recorded (a spectrum without any sample present)

The sample under analysis is sprayed (aspirated) into the flame decomposing the metallic compounds into metal atoms and ions.
The energies of the radiation from the lamp that match the energy transitions of the meal atoms in the flame are absorbed (this is why it’s called atomic absorption).

The absorbed energy is then re-radiated by the atoms in the flame in all directions, with little rejoining the incident beam.
Unabsorbed radiation is then transmitted through a monochromator to select one of the frequencies.

The selected radiation is sent to a detector which measures the absorbance value by measure the different between incident and transmitted radiation.