AQA GCSE Combined Science: Synergy Revision

12 mm = 12,000 µm; magnification = 12,000 ÷ 6 = ×2,000.

Active transport is needed because ions move against the concentration gradient; it requires energy from respiration.

Blood flow carries oxygen away and brings lower-oxygen blood, maintaining a concentration gradient across the thin alveolar wall.

Light is no longer the limiting factor over the plateau; some other factor is restricting photosynthesis rate.

Vaccination leaves specific memory cells, which recognise the antigen and support a faster antibody response on re-exposure.

No. The DNA may have changed without changing the phenotype, for example if the change does not alter a protein’s function.

A neutral atom has 11 electrons; losing one leaves 10 electrons. It is still the element with atomic number 11.

The forces cancel, so the horizontal resultant is 0 N; constant velocity is consistent with zero resultant force.

Total distance is 120 m, so average speed is 120/40 = 3.0 m s⁻¹. Displacement is zero, so average velocity is 0 m s⁻¹.

Aluminium is more reactive than carbon, so carbon cannot remove oxygen from aluminium oxide; electrolysis is needed to separate the aluminium.

It gives a net direction to random particle movement, from higher concentration toward lower concentration.

They help maintain a concentration gradient across the thin exchange surface so oxygen and carbon dioxide diffuse efficiently.

No. It changes probability; it does not guarantee an outcome for each individual.

Earth systems have many interacting variables and incomplete data, and models use simplifying assumptions.

The number of atoms of each element on both sides.

Yes. If the forces balance, the resultant is zero and its velocity can remain constant.

Acceleration.

Disposal can create waste or recover material/energy, changing the total life-cycle impact.

8 mm = 8,000 µm; magnification = 8,000 ÷ 40 = ×200.

(5.5−5.0) ÷ 5.0 ×100 = 10% gain.

Iodine changes from orange-brown to blue-black.

The pH 7 rate proxy is 1/60, twice 1/120, so the reaction is faster at pH 7.

Moving the lamp changes heating as well as light intensity; temperature itself affects photosynthesis rate.

To check consistency and calculate a more reliable mean reaction time.

It reduces selection bias by giving locations a more even chance of being sampled.

To remove unreacted solid while the dissolved salt remains in the filtrate.

The negative cathode.

Endothermic: the solution cooled as energy was taken in from the surroundings.

It doubles.

Rf = 3.0/6.0 = 0.50.

Water vaporises and condenses while most non-volatile dissolved salts remain in the original vessel.

c = E/(mΔT) = 2000/(0.50×10) = 400 J kg⁻¹ °C⁻¹.

A dull black surface.

In series with the wire.

A diode.

ρ = 30/10 = 3.0 g cm⁻³.

13−8 = 5 cm.

It halves, since a = F/m.

λ = v/f = 3.0/5 = 0.60 m.

It uses the observed data as evidence and explains how the pattern supports or challenges the prediction.

12 m ÷ 4 s = 3 m s⁻¹.

v = 4 × 0.75 = 3.0 m s⁻¹.

Another factor such as carbon dioxide concentration or temperature may be limiting.

Another factor, such as carbon dioxide concentration or temperature, has become limiting.

They move mucus containing trapped particles/pathogens away from the lungs.

Influenza is caused by a virus, while antibiotics act against bacteria.

Outgoing long-wavelength infrared radiation.

A transect with repeated sampling along its length.

Two recessive alleles, homozygous recessive.

Its wavelength.

n = 18 ÷ 18 = 1 mol.

They contain delocalised electrons that can move through the structure and carry charge.

Particles move faster and a greater fraction of collisions have at least the activation energy.

The assessment also considers extraction, manufacturing, packaging, transport and product use.