Science: Full Practice Paper 12 Worksheet with Answers

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CE.S-T12 Science: Full Practice Paper 12

ISEB COMMON ENTRANCE CE.S-T12 · Calculator allowed · about 60 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

1

Which gas do all living plant cells take in from the air, at all times, to release energy from glucose during respiration?

A) Carbon dioxide
B) Oxygen
C) Nitrogen
D) Hydrogen

(Total for Question 1 is 1 mark)

2

Which type of joint, found at the shoulder and hip, allows movement in many directions, including rotation?

A) Hinge joint
B) Ball and socket joint
C) Fixed (fused) joint
D) Pivot joint

(Total for Question 2 is 1 mark)

3

Complete the two missing words in these sentences about photosynthesis.

(a)The word equation for photosynthesis is: carbon dioxide + water -> glucose + ______ (using light energy).(1)

(b)Inside a plant cell, photosynthesis takes place mainly inside small structures called ______.(1)

(Total for Question 3 is 2 marks)

4

Which term describes a different version of a gene that can produce a different characteristic (for example, one version might give brown eyes, another blue eyes)?

A) Allele
B) Chromosome
C) Genome
D) Zygote

(Total for Question 4 is 1 mark)

5

Yusuf is investigating how temperature affects the rate of respiration in yeast. He mixes yeast with a glucose solution in a conical flask, connects the flask to a gas syringe, and places the flask into a water bath set to a particular temperature. He measures the volume of carbon dioxide gas produced in 5 minutes, then repeats the experiment at different temperatures.

Temperature (deg C): 15	25	35	45
Volume of CO2 produced in 5 minutes (cm3): 8	22	40	12

(a)Identify the independent variable in Yusuf's investigation.(1)

(b)State one variable that Yusuf kept the same to make this a fair test.(1)

(c)Describe the pattern shown by the results.(1)

(d)Explain, referring to enzymes, why the volume of gas produced decreases at 45 deg C.(1)

(Total for Question 5 is 4 marks)

6

Describe the job of each of these three parts of a reflex arc, which allows the body to respond very quickly to a stimulus, such as touching something hot: the receptor, the relay neuron (in the spinal cord), and the effector.

(Total for Question 6 is 3 marks)

7

A pupil's height increased from 140 cm to 154 cm over one year. Calculate the percentage increase in the pupil's height.

(Total for Question 7 is 2 marks)

8

Deepa is investigating how the concentration of glucose solution affects the rate of respiration in germinating pea seeds. She places germinating pea seeds into a respirometer containing a different concentration of glucose solution each time, and measures the volume of oxygen absorbed by the seeds in 20 minutes.

Concentration of glucose solution (%): 0	2	4	6
Volume of oxygen absorbed in 20 minutes (cm3): 3	9	15	16

(a)Identify the independent variable in Deepa's investigation.(1)

(b)State one variable that Deepa kept the same to make this a fair test.(1)

(c)Describe the pattern shown by the results.(1)

(d)Suggest why a higher concentration of glucose solution increases the rate at which the pea seeds absorb oxygen.(1)

(Total for Question 8 is 4 marks)

9

Farmers use selective breeding to improve dairy cattle, choosing which individual cows and bulls to breed together over many generations, in order to increase the amount of milk produced by their herd.

(a)State what is meant by selective breeding.(1)

(b)Explain how a farmer would choose which cattle to breed from, when trying to increase milk yield.(1)

(c)Explain why, after repeating this process over many generations, the average milk yield of the herd increases.(1)

(d)Suggest one disadvantage of using selective breeding in this way.(1)

(Total for Question 9 is 4 marks)

10

When a vaccination programme achieves a high enough percentage of a population being vaccinated against a particular infectious disease, this can protect the whole population, including people who have not been vaccinated themselves, an effect known as herd immunity. Explain how vaccinating a large percentage of a population can protect even the unvaccinated individuals within it.

(Total for Question 10 is 6 marks)

11

Which test result would confirm that a colourless gas collected during an experiment is ammonia?

A) Damp red litmus paper turns blue
B) A lit splint is extinguished with a squeaky pop
C) A glowing splint relights
D) Limewater turns cloudy (milky)

(Total for Question 11 is 1 mark)

12

Which group (family) of the periodic table contains unreactive gases, such as helium, neon and argon?

A) Group 1 (the alkali metals)
B) Group 7 (the halogens)
C) Group 0 (the noble gases)
D) The transition metals

(Total for Question 12 is 1 mark)

13

Complete the two missing words in these sentences about filtration, used to separate an insoluble solid from a liquid.

(a)The liquid that passes through the filter paper during filtration is called the ______.(1)

(b)The solid that remains on the filter paper during filtration is called the ______.(1)

(Total for Question 13 is 2 marks)

14

Which piece of equipment is used to measure the mass of a solid accurately, such as when weighing out a reactant for an experiment?

A) Measuring cylinder
B) Balance
C) Thermometer
D) Stopwatch

(Total for Question 14 is 1 mark)

15

Reuben is investigating how the concentration of copper sulfate solution affects the rate of a displacement reaction with iron powder. He adds the same excess mass of iron powder to 25 cm3 of copper sulfate solution of a different concentration each time, stirs the mixture, and records the maximum temperature reached, starting from a room temperature of 20 deg C.

Concentration of copper sulfate solution (mol/dm3): 0.2	0.4	0.6	0.8
Maximum temperature reached (deg C): 24	29	35	36

(a)Identify the independent variable in Reuben's investigation.(1)

(b)State one variable that Reuben kept the same to make this a fair test.(1)

(c)Describe the pattern shown by the results.(1)

(d)Explain, in terms of particles, why increasing the concentration of the copper sulfate solution increases the rate of this reaction.(1)

(Total for Question 15 is 4 marks)

16

Calculate the relative formula mass (Mr) of calcium carbonate, CaCO3. (Relative atomic masses: Ca = 40, C = 12, O = 16)

(Total for Question 16 is 2 marks)

17

Describe a test, including the positive result, that would show a substance produced in an experiment is: oxygen gas, carbon dioxide gas, and water (liquid).

(a)Oxygen gas.(1)

(b)Carbon dioxide gas.(1)

(c)Water (liquid).(1)

(Total for Question 17 is 3 marks)

18

Increasing the temperature of a reaction mixture increases the rate of a chemical reaction. Explain, in terms of collision theory, why this happens.

(a)State what must happen between particles for a chemical reaction to occur.(1)

(b)Explain the effect of increasing temperature on the particles in a reaction mixture.(1)

(c)Explain the effect increasing temperature has on the frequency of collisions between reacting particles.(1)

(d)Explain the effect increasing temperature has on the proportion of collisions that result in a reaction, and hence on the overall rate of reaction.(1)

(Total for Question 18 is 4 marks)

19

Complete the missing words in these sentences about pH and indicators.

(a)A solution with a pH value below 7 is ______.(1)

(b)A solution with a pH value above 7 is ______.(1)

(c)Universal indicator turns ______ in a neutral solution, which has a pH of exactly 7.(1)

(Total for Question 19 is 3 marks)

20

Metals, such as copper and aluminium, are good conductors of electricity, and can also be bent or hammered into different shapes without breaking (they are malleable). Explain, in terms of the structure and bonding of a metal, why metals conduct electricity and are malleable.

(Total for Question 20 is 6 marks)

21

Which unit is used to measure the frequency of a wave?

A) Hertz (Hz)
B) Watt (W)
C) Newton (N)
D) Pascal (Pa)

(Total for Question 21 is 1 mark)

22

Which piece of equipment is used to measure the potential difference (voltage) across a component in a circuit?

A) Ammeter
B) Voltmeter
C) Barometer
D) Thermometer

(Total for Question 22 is 1 mark)

23

Complete the two missing words in these sentences about electricity.

(a)The rate of flow of electric charge around a circuit is called the ______.(1)

(b)The push (energy transferred per unit charge) that drives current around a circuit is called the ______ (or voltage).(1)

(Total for Question 23 is 2 marks)

24

Naomi is investigating how the mass hung on a spring affects the time period of its oscillations. She hangs a different mass on the spring each time, pulls the mass down by the same small amount and releases it, then uses a stopwatch to measure the time for 10 complete oscillations (up-and-down swings).

Mass hung on spring (g): 50	100	150	200
Time for 10 oscillations (s): 4.2	5.9	7.3	8.4

(a)Identify the independent variable in Naomi's investigation.(1)

(b)State one variable that was kept the same to make this a fair test.(1)

(c)Describe the pattern shown by the results.(1)

(d)Calculate the time period (the time for one oscillation) when a mass of 100 g is used.(1)

(Total for Question 24 is 4 marks)

25

A crane lifts a load of mass 50 kg vertically upwards through a height of 4 m, at a steady speed. (Gravitational field strength, g = 10 N/kg)

(a)Calculate the weight of the load, using weight = mass x gravitational field strength.(1)

(b)Calculate the work done by the crane in lifting the load through this height, using work done = force x distance.(2)

(Total for Question 25 is 3 marks)

26

Describe how each of these three renewable energy resources is used to generate electricity: solar (photovoltaic) cells, wind turbines, and hydroelectric power stations.

(Total for Question 26 is 3 marks)

27

A dam is used to hold back a large reservoir of water. The pressure of the water pushing on the dam wall is not the same at every depth.

(a)State how the pressure in a liquid changes with depth.(1)

(b)Explain, in terms of the liquid above a point, why pressure increases with depth.(1)

(c)Explain why a dam wall holding back a reservoir of water is built thicker at its base than near the top.(1)

(d)Predict, giving a reason, how the pressure at the base of the dam would differ if the reservoir contained a denser liquid instead of water, at the same depth.(1)

(Total for Question 27 is 4 marks)

28

Talia is investigating how the volume of water in a set of identical glass bottles affects the pitch of the note produced when she blows air across the top of each bottle.

Volume of water in bottle (cm3): 100	200	300	400
Frequency (pitch) of note (Hz): 220	294	370	440

(a)Identify the independent variable in Talia's investigation.(1)

(b)State one variable that Talia kept the same to make this a fair test.(1)

(c)Describe the pattern shown by the results.(1)

(d)Explain, in terms of the column of air inside the bottle, why more water in the bottle produces a note with a higher pitch.(1)

(Total for Question 28 is 4 marks)

29

A hairdryer transfers 1200 W of power when connected to the UK mains supply of 230 V. Calculate the current flowing through the hairdryer, using power = potential difference x current.

(Total for Question 29 is 2 marks)

30

The greenhouse effect keeps the Earth's average temperature warm enough to support life, but increased levels of greenhouse gases, such as carbon dioxide, released by human activities are enhancing this effect, leading to global warming. Explain how greenhouse gases in the atmosphere cause the greenhouse effect, and how human activities are enhancing it.

(Total for Question 30 is 6 marks)

Mark scheme · CE.S-T12 Science: Full Practice Paper 12

Question 1

B1 B cao
Answer: B) Oxygen

Question 2

B1 B cao
Answer: B) Ball and socket joint

Question 3

(a) B1 oxygen cao
(a) Answer: Oxygen
(b) B1 chloroplasts (accept chloroplast) cao
(b) Answer: Chloroplasts

Question 4

B1 A cao
Answer: A) Allele

Question 5

(a) B1 the temperature of the water bath oe
(a) Answer: The temperature of the water bath.
(b) B1 any one of: the volume/concentration of glucose solution; the mass (amount) of yeast; the time over which gas is collected (5 minutes) oe
(b) Answer: For example, the volume and concentration of glucose solution used.
(c) B1 as temperature increases from 15 to 35 deg C, the volume of CO2 produced increases, but between 35 and 45 deg C the volume produced decreases sharply oe
(c) Answer: As temperature increases from 15 to 35 deg C, the volume of CO2 produced increases, but between 35 and 45 deg C it decreases sharply.
(d) B1 at high temperatures such as 45 deg C, the enzymes in the yeast cells that catalyse respiration become denatured (their shape, including the active site, changes), so they can no longer catalyse the reaction effectively, decreasing the rate of respiration and CO2 production oe
(d) Answer: At 45 deg C the enzymes that catalyse respiration in the yeast cells become denatured, so they can no longer work effectively, decreasing the rate of respiration and CO2 production.

Question 6

B1 the receptor detects the stimulus (e.g. heat) and generates an electrical (nerve) impulse oe
B1 the relay neuron, in the spinal cord, passes the impulse from a sensory neuron to a motor neuron, without the message having to travel all the way to the brain first, allowing a very fast response oe
B1 the effector (a muscle or gland) carries out the response, e.g. a muscle contracts to pull the hand away oe
Answer: The receptor detects the stimulus. The relay neuron in the spinal cord passes the impulse on quickly, without going via the brain. The effector (muscle or gland) carries out the response.

Question 7

M1 correct substitution: percentage increase = (154 - 140) / 140 x 100 oe
A1 10% cao
Answer: 10%

Question 8

(a) B1 the concentration of the glucose solution oe
(a) Answer: The concentration of the glucose solution.
(b) B1 any one of: the number (or mass) of pea seeds used; the time over which oxygen absorption is measured (20 minutes); the temperature oe
(b) Answer: For example, the number of pea seeds used each time.
(c) B1 as the concentration of glucose solution increases, the volume of oxygen absorbed increases, although the increase becomes smaller between 4% and 6% oe
(c) Answer: As glucose concentration increases, the volume of oxygen absorbed increases, although the increase is smaller between 4% and 6%.
(d) B1 glucose is the substrate used in respiration (glucose + oxygen -> carbon dioxide + water, releasing energy); a higher concentration of glucose gives the seeds' cells more respiratory substrate available, allowing them to respire (and use oxygen) at a faster rate oe
(d) Answer: Glucose is the substrate used in respiration, so a higher concentration gives the seeds' cells more substrate available, allowing them to respire, and use oxygen, at a faster rate.

Question 9

(a) B1 humans choose organisms with the most useful or desired characteristics (e.g. highest milk yield) to breed together oe
(a) Answer: Humans choose organisms with the most useful characteristic (e.g. highest milk yield) to breed together.
(b) B1 the farmer selects the cows and bulls whose own record (or whose close relatives) show the highest milk yield, and breeds them together as the parents of the next generation oe
(b) Answer: The farmer selects the cows and bulls with the highest milk yield (or whose relatives have the highest yield) as the parents of the next generation.
(c) B1 offspring inherit alleles for high milk yield from their selected parents; because this selection is repeated every generation, alleles for high milk yield become more common in the herd, so average milk yield increases generation after generation oe
(c) Answer: Offspring inherit alleles for high milk yield from their selected parents; repeating this every generation makes these alleles more common, so average milk yield rises over time.
(d) B1 any suitable disadvantage, e.g. it reduces genetic variation within the herd, making the cattle more genetically similar and so more vulnerable as a group to a new disease; or selectively bred cattle may develop other health problems as a result of reduced variation oe
(d) Answer: For example, it reduces genetic variation in the herd, making the cattle more genetically similar and so more vulnerable as a group to a new disease.

Question 10

Level 1 (1-2): Basic, isolated statement(s) about vaccination or infection, with little or no reference to how the wider population is protected.
Level 2 (3-4): Some relevant ideas about vaccinated people becoming immune, or not spreading the disease, are given, but the explanation of why unvaccinated people are protected as a result is incomplete or not fully linked.
Level 3 (5-6): A clear, logically linked explanation of how vaccination makes individuals immune, so that if enough of the population is immune, a pathogen entering the population finds very few susceptible people to infect, breaking the chain of transmission and reducing the chance it ever reaches the smaller number of unvaccinated individuals.
Indicative content:
- A vaccine contains a small, harmless amount of a dead or weakened pathogen (or a fragment/antigen of it).
- This causes the body's immune system to produce antibodies specific to that pathogen, without the person suffering the disease itself.
- The body also produces memory cells, so a vaccinated person can respond quickly and produce antibodies rapidly if they later encounter the real pathogen, making them immune (protected from becoming ill).
- If a high enough percentage of the population is vaccinated (immune), then most of the people a pathogen could potentially infect are already immune to it.
- This means the pathogen finds it much harder to pass from an infected person to a new susceptible person, because so many of the people it might come into contact with cannot be infected.
- The chain of transmission of the disease through the population is broken (or greatly slowed), so the disease cannot spread easily or rapidly, reducing the risk that it ever reaches the smaller number of people who are not vaccinated, protecting them indirectly through herd immunity.

Question 11

B1 A cao
Answer: A) Damp red litmus paper turns blue

Question 12

B1 C cao
Answer: C) Group 0 (the noble gases)

Question 13

(a) B1 filtrate cao
(a) Answer: Filtrate
(b) B1 residue cao
(b) Answer: Residue

Question 14

B1 B cao
Answer: B) Balance

Question 15

(a) B1 the concentration of the copper sulfate solution oe
(a) Answer: The concentration of the copper sulfate solution.
(b) B1 any one of: the volume of copper sulfate solution (25 cm3); the mass of iron powder (in excess each time); the starting temperature oe
(b) Answer: For example, the volume of copper sulfate solution used.
(c) B1 as the concentration of copper sulfate solution increases, the maximum temperature reached increases, although the increase becomes smaller between 0.6 and 0.8 mol/dm3 oe
(c) Answer: As copper sulfate concentration increases, the maximum temperature reached increases, although the increase is smaller between 0.6 and 0.8 mol/dm3.
(d) B1 a more concentrated copper sulfate solution has more copper ions (Cu2+) in the same volume, so there are more frequent collisions between iron atoms and copper ions, increasing the rate of the (exothermic) reaction, so heat is released more quickly oe
(d) Answer: A more concentrated copper sulfate solution has more copper ions in the same volume, causing more frequent collisions with the iron powder and increasing the rate of the exothermic reaction, so heat is released more quickly.

Question 16

M1 correct substitution: Mr = 40 + 12 + (16 x 3) oe
A1 100 cao
Answer: 100

Question 17

(a) B1 hold a glowing splint in the gas; the splint relights oe
(a) Answer: Hold a glowing splint in the gas; it relights.
(b) B1 bubble the gas through limewater; the limewater turns cloudy (milky) oe
(b) Answer: Bubble the gas through limewater; it turns cloudy (milky).
(c) B1 add the liquid to white anhydrous copper sulfate (powder); it turns blue oe
(c) Answer: Add the liquid to white anhydrous copper sulfate; it turns blue.

Question 18

(a) B1 reacting particles must collide with each other, with at least a minimum amount of energy (called the activation energy) oe
(a) Answer: Reacting particles must collide with each other with at least a minimum amount of energy, called the activation energy.
(b) B1 increasing temperature gives the reacting particles more kinetic energy, so they move around faster oe
(b) Answer: Increasing temperature gives the particles more kinetic energy, so they move faster.
(c) B1 because the particles are moving faster, they collide with each other more often (more frequently) in a given time oe
(c) Answer: Because the particles move faster, they collide with each other more frequently in a given time.
(d) B1 because the particles have more energy, a greater proportion of collisions have at least the activation energy needed to react (successful collisions); combined with the increased collision frequency, this increases the rate of reaction oe
(d) Answer: A greater proportion of collisions now have enough energy to react successfully, and combined with the higher collision frequency, this increases the overall rate of reaction.

Question 19

(a) B1 acidic (accept an acid) cao
(a) Answer: Acidic
(b) B1 alkaline (accept an alkali/basic) cao
(b) Answer: Alkaline
(c) B1 green cao
(c) Answer: Green

Question 20

Level 1 (1-2): Basic, isolated statement(s) about metal atoms or electrons, with little or no reference to a lattice structure or delocalised electrons.
Level 2 (3-4): Some relevant ideas about metal ions or free electrons are given, but the explanation linking structure to conductivity and/or malleability is incomplete or not fully linked.
Level 3 (5-6): A clear, logically linked explanation of the giant metallic lattice of closely packed positive metal ions surrounded by a sea of delocalised electrons, explaining both electrical conductivity (electrons free to move and carry charge) and malleability (layers of ions sliding over each other without breaking metallic bonds).
Indicative content:
- A metal consists of a giant structure (lattice) of positively charged metal ions, arranged in regular, closely packed layers.
- Each metal atom loses its outer shell electron(s), which become delocalised (free to move) throughout the whole structure, rather than staying attached to one particular atom.
- These delocalised (free) electrons and the positive metal ions are held together by strong electrostatic forces of attraction, called metallic bonding, throughout the lattice.
- Because the delocalised electrons are free to move throughout the structure, they can carry electrical charge through the metal when a potential difference is applied, which is why metals conduct electricity.
- Because the layers of positive metal ions can slide over each other when a force is applied, without breaking the strong metallic bonds (as the delocalised electrons can still move to hold the new arrangement together), the metal can change shape without shattering, which is why metals are malleable (and ductile).
- This is different from ionic or covalent structures, where electrons are not delocalised in the same way, so those structures generally do not conduct electricity as solids and tend to shatter rather than bend when a force is applied.

Question 21

B1 A cao
Answer: A) Hertz (Hz)

Question 22

B1 B cao
Answer: B) Voltmeter

Question 23

(a) B1 current cao
(a) Answer: Current
(b) B1 potential difference cao
(b) Answer: Potential difference

Question 24

(a) B1 the mass hung on the spring oe
(a) Answer: The mass hung on the spring.
(b) B1 any one of: the spring used; the distance the mass was pulled down before release (the amplitude); the number of oscillations timed (10) oe
(b) Answer: For example, the same spring was used each time.
(c) B1 as the mass hung on the spring increases, the time for 10 oscillations increases (the oscillations become slower) oe
(c) Answer: As the mass hung on the spring increases, the time for 10 oscillations increases, so the oscillations become slower.
(d) B1 0.59 s cao (working: 5.9 / 10)
(d) Answer: 0.59 s

Question 25

(a) B1 500 N cao (working: 50 x 10)
(a) Answer: 500 N
(b) M1 correct substitution: work done = 500 x 4 oe (ft from (a))
(b) A1 2000 J cao
(b) Answer: 2000 J

Question 26

B1 solar (photovoltaic) cells transfer light energy from the Sun directly into electrical energy, using panels made from special materials (semiconductors) oe
B1 wind turbines use the kinetic energy of moving air (wind) to turn blades connected to a generator, transferring this kinetic energy into electrical energy oe
B1 hydroelectric power stations use the kinetic energy of falling or flowing water (often released from a reservoir behind a dam) to turn a turbine connected to a generator, transferring the water's energy into electrical energy oe
Answer: Solar cells transfer light energy from the Sun directly into electrical energy. Wind turbines use moving air to turn blades connected to a generator. Hydroelectric power stations use falling or flowing water to turn a turbine connected to a generator.

Question 27

(a) B1 pressure in a liquid increases with depth oe
(a) Answer: Pressure in a liquid increases with depth.
(b) B1 at a greater depth, there is a taller (greater) column/weight of liquid above that point, pressing down on it, so the pressure at that point is greater oe
(b) Answer: At a greater depth, there is a taller, heavier column of liquid above that point pressing down, so the pressure is greater.
(c) B1 the water pressure (and so the force pushing on the dam) is greatest at the base of the dam, where the water is deepest, so the wall needs to be thicker there to withstand this greater force without breaking oe
(c) Answer: Water pressure is greatest at the base of the dam, where the water is deepest, so the wall must be thicker there to withstand the greater force pushing on it.
(d) B1 the pressure would be greater, because a denser liquid has more mass (and so more weight) in the same volume above that point, increasing the pressure at the same depth oe
(d) Answer: The pressure would be greater, because a denser liquid has more mass, and so more weight, in the same volume above that point.

Question 28

(a) B1 the volume of water in the bottle oe
(a) Answer: The volume of water in the bottle.
(b) B1 any one of: the bottle used (its size/shape); how hard or in what way she blew across the top oe
(b) Answer: For example, an identical bottle was used each time.
(c) B1 as the volume of water in the bottle increases, the frequency (pitch) of the note produced increases oe
(c) Answer: As the volume of water in the bottle increases, the frequency of the note produced increases.
(d) B1 more water in the bottle leaves a shorter column of air above it; a shorter column of air vibrates at a higher frequency (completes more vibrations per second) when blown across, producing a higher-pitched note oe
(d) Answer: More water leaves a shorter column of air above it, and a shorter air column vibrates at a higher frequency, producing a higher-pitched note.

Question 29

M1 correct substitution: current = 1200 / 230 oe
A1 5.2 A (awrt 5.2) cao
Answer: 5.2 A

Question 30

Level 1 (1-2): Basic, isolated statement(s) about greenhouse gases or global warming, with little or no reference to how radiation is absorbed or re-radiated.
Level 2 (3-4): Some relevant ideas about greenhouse gases trapping heat or human activities releasing more of them are given, but the explanation of how this warms the Earth's surface, or how it becomes enhanced, is incomplete or not fully linked.
Level 3 (5-6): A clear, logically linked explanation of how short-wave radiation from the Sun warms the Earth's surface, which re-emits long-wave (infra-red) radiation that greenhouse gases absorb and re-radiate back towards the surface, and how increased greenhouse gas concentrations from human activity enhance this natural effect, raising average temperature.
Indicative content:
- Short-wave radiation from the Sun passes through the atmosphere and is absorbed by the Earth's surface, warming it.
- The warmed surface of the Earth re-emits this energy as long-wave (infra-red) radiation, some of which travels back out towards space.
- Greenhouse gases in the atmosphere, such as carbon dioxide and methane, absorb some of this outgoing long-wave (infra-red) radiation.
- These gases then re-radiate the absorbed energy in all directions, including back towards the Earth's surface, rather than letting all of it escape into space.
- This keeps the Earth's surface and lower atmosphere warmer than they would otherwise be, which is the natural greenhouse effect, essential for maintaining a temperature able to support life.
- Human activities, such as burning fossil fuels, release extra greenhouse gases (e.g. carbon dioxide) into the atmosphere, increasing their concentration; this means more infra-red radiation is absorbed and re-radiated back to the surface, enhancing the greenhouse effect and causing the Earth's average temperature to rise (global warming) beyond its natural level.

Science: Full Practice Paper 12 - Worksheets, Questions and Revision

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CE.S-T12 Science: Full Practice Paper 12

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