metals, air and water

Question 1

extraction from ores

Answer 1

• metals at the bottom of the reactivity series (Ag, Au and Pt) are found as the uncombined metal in nature
• metals below carbon can be extracted from their ores by reduction using carbon or carbon monoxide
• metals above carbon in the reactivity series must be extracted using electrolysis

Question 2

displacement reactions

Answer 2

-when a more reactive metal replaces a less reactive metal in a dissolved compound

Question 3

alloy

Answer 3

two or more metals mixed together to combine properties

Question 4

transition metals

Answer 4

• commonly used as catalysts
• usually lose 2 electrons to for 2+ ions
• high density
• high mp
• generally unreactive

Question 5

air

Answer 5

• nitrogen (78%)
• oxygen (21%)
• argon (0.9%)
• carbon dioxide (0.04%)
• water vapour (up to 5% depending on humidity)

Question 6

greenhouse gases

Answer 6

• these gases maintain temps on Earth high enough to support life
• e.g. CO2, CH4 and water vapour
• as energy from the Sun reaches the Earth, greenhouse gases allow short wavelength radiation, e.g. UV and visible light, to pass through, heating the Earth surface
• as the Earth cools, it emits longer wavelength radiation, e.g. infrared radiation (IR)
• greenhouse gases absorb IR, so some energy radiated from the Earth is trapped in the atmosphere -> temp rises
• the higher the proportion of greenhouse gases in the atmosphere, the more energy is absorbed

Question 7

human activities that have caused increases in the levels of CO2 and CH4

Answer 7

CO2: -deforestation
-burning of fossil fuels

CH4: -cattle farming

      - rice fields
      - landfill sites

Question 8

air pollution

Answer 8

• caused by the release of poisonous/harmful chemicals into the air which directly/indirectly harm living things, damage the environment and buildings
• most pollutants come from the burning of fossil fuels

Question 9

carbon monoxide

Answer 9

• a colourless, odourless, poisonous gas
• it binds more strongly to haemoglobin than oxygen and greatly reduces the amount of oxygen that the blood can carry around the body

Question 10

sulfur dioxide

Answer 10

• a poisonous, colourless, acidic gas with a choking smell
• causes breathing difficulties and triggers asthma attacks
• reacts with water and O2 in the atmosphere to produce sulfuric acid, one of the components of ‘acid rain’
• acid rain erodes stonework, increases metal corrosion, increases the leaching of soil (removal of important minerals) and is harmful to animal and plant life

Question 11

nitrous oxides

Answer 11

• at the high temps and pressures generated within burner units, nitrogen in the air can react with oxygen to give different oxides of nitrogen
• can react with O2 and water in the atmosphere to generate nitric acid, a component of acid rain
• toxic
• can trigger asthma attacks

Question 12

water

Answer 12

• chemicals are added to water to make it safe to drink
• chlorine gas is added in controlled quantities to sterilise the water as it kills harmful bacteria.
• fluoride ions may be added as fluoride helps protect against tooth decay

Question 13

metal reaction with water

Answer 13

metal + water -> metal hydroxide + hydrogen gas

metal + steam -> metal oxide + hydrogen gas

Question 14

ductile meaning

Answer 14

-when a metal is able to be drawn out into a thin wire

Question 15

malleable meaning

Answer 15

-when a metal is able to be hammered or bent into shape without breaking or cracking

Question 16

electroplating

Answer 16

• cathode should be the object to be electroplated (e.g. iron)
• anode should be the metal that you want to coat the object with (e.g. copper)
• electrolyte should be a solution of the coating metal (e.g. copper sulphate)