H

• Explain why the star is stable while it is in the main sequence stage of its life cycle.

  Gravitational forces are pushing inwards and the force due to fusion pushing outwards are balanced
• Describe what will happen to the star between the main sequence stage and the end of the star's life cycle.

  • Expand become a red
  • Collapse to become a white dwarf
  • Cool down to become a black dwarf
• Describe the life cycle of stars much more massive than the Sun, including the formation of new elements.

  1)Hydrogen gas and dust in the nebula is brought together by gravity

  2)A protostar is formed and the star heats up

  3)Eventually the star is hot enough that hydrogen is fused into helium, this is called the main sequence stage

  4)Eventually hydrogen runs out and helium fusion occurs up to Iron

  5)The star then expands to become a red supergiant

  6)The red supergiant then explodes in the form of a supernova and scatters the new element everywhere
• Describe how ethanol is produced from sugar solution

  fermentation in the absence of oxygen at a temperature of 45 degrees
• Methylated spirit also contains:

  • pyridine which has a very unpleasant smell
  • methyl violet which makes the mixture purple.

  Suggest why pyridine and methyl violet are added to ethanol to make methylated spirit.

  To deter consumption
• The percentages of carbon dioxide and oxygen have changed from Earth's early atmosphere to Earth's atmosphere today.

  Explain the processes that led to these changes.

  Carbon dioxide dissolved in the ocean which resulted in carbonates to produce sediments so the num of carbon dioxide decreased

  algae/plans absorbed carbon dioxide

  during photosynthesis and released oxygen
• Explain how carbon monoxide is produced when petrol is burned in car engines.

  Incomplete combustion due to lack of oxygen
• Give one reason for having allowed an maximum allowed percentage of unburned hydrocarbon in exhaust flame

  Health problems
• Describe how oxides of nitrogen are produced when petrol is burned in car engines

  nitrogen (from atmosphere)

  reacts with oxygen (from atmosphere)

  at high temperature (in engine)
• Give two effects of atmospheric pollution which are reduced by using catalytic converters.

  Carbon monoxide

  acid rain
• The reaction is carried out at a temperature of 250 °C and a pressure of 100 atmospheres.

  The forward reaction is exothermic.

  what happens to the yield of methanol if a temperature higher than 250 °C

  Smaller yield as equilibrium shifts to the left
• A pressure of 100 atmospheres is used instead of atmospheric pressure.

  Tractigher pressure gives a greater yield of methanol and an increased rate of

  Explain why.

  equilibrium position moves to the product side

  (because) fewer molecules

  more molecules per unit volume

  (because) more molecules per unit volume

   
• Melamine is a polymer used to make non-disposable cups.

  Melamine does not melt when it is heated.

  Melamine is a thermosetting polymer which means that it can decompose
• Explain how the person's eye could adjust to form a clear image of a near object

  Cillary muscle contract so they have a smaller diameter and suspensory ligmantes loosen the lens thickens so light is refracted so the image is focused on the retina
• Explain why long sighted person has difficulty seeing near object clearly

  The lens cannot be thickened enough so light is focused behind the retina
• Long sightedness can be corrected by wearing spectacles

  Describe how spectacle lens can correct long sightedness

  Cove lens is used to refract light rays in wards so light can be focused onto the retina
• 1)Several groups of cells are scrapped off the leaf

  2) Nutrients are add to the agar jelly

  3) Hormones are added to adgar jelly

  4)The plant cells are kept in sterile conditions

  5)The plant cells are kept and 20 degrees

  1)so that many plants can be produced

  2) provides energy

  3) so roots and shoots can develop

  4)to prevent microorganisms from entering

  5) optimum temperature for grow
• What gland releases the hormone that controls water loss from the body

  Pituitary
• What hormone helps the kidney to control water loss from the body

  ADH
• Explain why ADH and the kidney reduce water loss

  A higher concentration of blood which causes more ADH to be released. ADH increases the permeability of the kidney tubules to water. So an increased amount of water is being reabsorbed into the blood stream
• Explain to biological reasons why most doctors think that the a kidney transplant is a better method of treatment that dialysis

  Blood not in contact with dialysis machine so less chance of infection

  Changes in concentration so less chance of causing damage to body
• Explain the advantage of making crop plant resistance to glyphosate

  Causes the glyphosate to kill the weeds not the crop

  Less competition light, water, soil

  So crops have higher yield
• Suggest two reasons why bitumen is not used as a fuel.

  1)Too viscous

  2) not very flammable
• Explain why large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules.

  There is more of a demand for small molecules and smaller chain molecules are more useful
• what type of polyester melt when it is heated?

  Thermosoftening polyester because it has weak intermolecular forces
• Suggest two reasons why an outer skin is added to the poly(styrene) core.

  Stronger

  harder
• Suggest two reasons why wood is more sustainable than natural gas as a fuel for central heating boilers.

  Wood is renewable

  carbon neutral
• Explain how greenhouse gas keeps Titan warmer than the other moons of Saturn.

  Methane allows a short wavelength radiation to pass through which then. re- emits and then absorbed by methane in the atmosphere
• The catalyst for the reaction is manganese dioxide

  Describe a test to identify the gas produced in the reaction.

  Give the result of the test

  Test:glowing splint

  Result: which relights
• The rate of reaction is different when manganese dioxide is used as a fine powder rather than coarse lumps.

  You should answer in terms of collision theory.

  manganese dioxide powder has a greater surface area so more

  collisions per unit time
•  Explain why a low pressure is used in stage 1.

  Give your answer in terms of equilibrium.

  higher yield (of hydrogen or carbon monoxide or product)(because) fewer moles on left hand side
• CO(g) + H20(g) = COz(g) + H2(g)

  What is the effect of increasing the pressure on the equilibrium yield of hydrogen stage 2?

  no effect
• A pressure of 285 atmospheres is not used in the Haber process instead of 200 atmospheres.

  Give one reason why.

  high(er) pressures are (more)

  dangerous
• How does Figure 10 show that the forward reaction in the Haber process is exothermic?

  higher Temperature produces a lower yield of ammonia
• Suggest why the demand for ammonia has increased.

  world population has increased