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Unit 5: Water We Drink APPLICATION QUESTION

Question One:

Distillation. Impure water is evaporated, and pure water condenses on the plastic foil. The water then drips down into the cup collecting the pure water that is consumable.

Or we can just purchase water purifying equipment for hiking, like Ultraviolet Light Water Purifier.

Question Two:

Desalination using reverse osmosis techniques is costly to maintain the condition of the technology used, and it requires a high-energy consumption. Places usually use this where they do not have natural resources of water. (Eg. Singapore.) If they have natural resources, cities will use other cheaper ways to purify water, such as distillation.

Desalination will cause environmental problems as well, upsetting the ecosystem, and affect marine life since water is needed to be pumped from the sea, and pipes may vacuum and kill the marine-organisms.

Question Three:

  1. The main source is from the pipes that contain lead. The lead is dissolved into the water.
  2. In a chemistry lab, we practice the separation of aqueous and chlorinated waste. We do not dispose the lead into the sink. Hence, research activities cannot account for the elevated lead levels, unless someone do not practice safe disposal of chemical waste.

Question Four:

Whether the solute is soluble is dependent on the energy required to overcome the bonds between the solute-solute and solvent-solvent molecules, and the energy released due to the bonds formed between the solute and solvent molecules.

Water-soluble molecules would be polar compounds, due to similar bonding between water molecules being polar as well. The energy absorbed for bond breaking will be sufficiently compensated for the energy released from the bond formation between solute and solvent molecules.

Though a fat-soluble compound is often non-polar as fats are usually non-polar. This similarity in the polarity of the solute and solvent will result in sufficient energy for compensation provided by the bond formation, to support the bond breaking, making the reaction of solubility favourable.

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Unit 3: The Chemistry of Global Climate Change APPLICATION QUESTIONS

Question 1:

The presence of greenhouse gases absorbs and traps the energy radiated by the Earth, thus heating up the atmosphere. Clouds are composed of water vapor, which is a strong greenhouse gas, thus contributing to the heating up of the atmosphere, so the Earth is not cooling rapidly.

Question 2:

The statement is incorrect. Global warming will upset the climate system and cause extreme weather. Some places will experience extreme heat waves, droughts, while other places will experience excessive precipitation and colder-than-before weather. Despite the image showing the people experiencing extreme cold weather and are in knee-deep snow, there is still global warming, and it is the cause of the extreme weather the people in the image are experiencing.

Question 3:

The absorption of microwaves by water molecules will interfere with detection of intended objects. This is since the water molecules will absorb the microwaves instead. Thus, the design in unsuccessful.

Question 4:

In the short run, the most serious situation is the bad air quality. The particles in the air will cause direct health problems such as respiratory problems.

Global warming has more drastic consequences, due to the rising sea levels caused by glacial retreat, and extreme climates. This will affect the survival of living organisms.

Depletion of ozone directly affects a certain area of the Earth. There are precautions then individual can take to prevent the UV rays from affecting us. Such as sunblock and sunscreen)

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Unit 4: Energy from Combustion APPLICATION EXERCISE

 

Question 1

a: exothermic. We feel hot when we put our hands near the burning charcoal

b: endothermic. We feel a cooling sensation when the water evaporates from our skin.

c: endothermic. Our hands feel cold when we put it near an ice cube.

Question 2

Bond energy of products should be much lesser than the reactants, in order to release a large amount of energy.

change in enthalpy = bond energy of products – bond energy of reactants

Question 3

Temperature is really just a measure of the vibrational energy of the particles. It can be directly measured using the Fahrenheit, Celsius and Kelvin scale.

For heat, it is a measure of the difference in temperature. For example, we submerge our right hand into ice water and left hand into hot water. Then remove both hands from the water and submerge both in lukewarm water. The right hand will feel cold while the left hand will feel hot. This is due to the difference in temperature.

Question 4

a: An octane number of 98 means a knocking characteristics of 98% isooctane and 2% heptane.

b: Fuels containing oxygenates would usually have an octane rating of higher than 100. Typically, fuels of octane rating of 98 to 100 do not contain oxygenates. Thus, the fuel does not contain oxygenates.

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First post

I have found out that blue and purple meant that the area has the least ozone whereas red, yellow, green meant that the area has the most amount of ozone. ozone-2-369685

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Unit 2: Protecting the Ozone Layer

I learnt about how ozone is being formed and depleted at the same rate, giving rise to its steady state. The ozone layer helps to protect us from the harmful ultraviolet rays from the sun, which might bring about health problems such as skin cancer. I also found out about the 3 different types of UV radiation, UV-A, UV-B and UV-C. 

ozone

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Ozone

Majority of the ozone in the atmosphere exists in the stratosphere.

The function of the ozone is to absorb the ultraviolet radiation, preventing a large percentage of ultraviolet radiation from reaching the Earth’s surface.

uv_absorption

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Ozone layer

Ozone in the stratosphere absorbs ultraviolet radiation.

Ozone in the troposphere is harmful to man.

Red has the greatest wavelength, which corresponds to lowest energy.

UV-C is the most harmful among UV-A, UV-B and UV-C.

ozone1

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Ozone layer

Ozone layer is a layer found in stratosphere that prevents harmful  uv rays from reaching humans. However, due to the use of CFCs, there is a hole in the ozone layer above the Antarctica. Hence, more friendly HFCs are used as they are environmetally  friendly as they does not contain chlorine atoms.

 

 

ozone_hole_nasa

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Ozone Layer

90% of the ozone layer is found in the stratosphere. Ozone actually protects us humans from the harmful UV radiation. However, in recent years, the ozone layer is depleting and the main cause is probably due to CFCs. Chlorine atoms destroy the ozone layer. If this prolongs, we will be more exposed to the harmful UV radiation which may cause skin cancer. In 1989, countries have step up and banned the production of CFCs to prevent the ozone layer from further depletion.

ozone1