water

Question 1

Chemical tests to identify the presence of water:

Answer 1

• Cobalt(II) chloride
  
  • Cobalt (II) chloride paper is blue when dry but turns pink in contact with water
• Copper(II) sulfate
  
  • Copper(II) sulfate is white when anhydrous but turns blue in contact with water

Question 2

Testing water purity:

Answer 2

• If it freezes at exactly 0
• It it boils at exactly 100

Question 3

Substances that can be found in water:

Answer 3

• Dissolved oxygen
• Metal compounds
• Plastics
• Sewage and harmful microbes
• Nitrates and phosphates from fertilizers

Question 4

NPK fertilizers consist of:

Answer 4

• Nitrogen (N)
  
  • Phosphorus (P)
  • Potassium (K)
  • Salts like potassium nitrate (KNO3) and ammonium phosphate (NH4PO4)

Question 5

why can’t plants use nitrogen in the air?

Answer 5

• because it is found as a diatomic molecule which has an incredibly strong triple bond and they have no way of breaking this bond
• Plants can only use nitrogen when it is found in more reactive compounds like the nitrate ion (NO3ˆ-) or ammonium (NH4ˆ+)

Question 6

why is the haber process important in food production?

Answer 6

because it breaks the very strong N-to-N triple bond and converts the nitrogen in our air into a form that plants can use, increasing food production

Question 7

clean dry air consists of

Answer 7

• Clean, dry air: 78% nitrogen, 21% oxygen, 1% others

Question 8

where do carbon dioxide emissions come from?

Answer 8

burning of fossil fuels

Question 9

how/when is methane released?

Answer 9

when plant material decomposes, but also from the digestion of food by intensively-farmed animals like cows

Question 10

source of acid rain

Answer 10

Sulfur dioxide produced when fuels containing sulfur impurities are burned, especially coal

Question 11

what do catalytic converters do?

Answer 11

they can remove both oxides of nitrogen and carbon monoxide from exhaust gases:
- 2CO + 2NO → 2CO2 + N2