Chemistry
Enzymes
Respiration and Photosynthesis
Electricity
100

What is the atomic number of an element?

The number of protons in the nucleus.

100

What is the name of the place where a substrate binds to an enzyme?

Active site

100

What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen (plus chlorophyll and sunlight)

100

What device is used to measure current in a circuit?

Ammeter

200

What type of bonding occurs between sodium and chlorine?

Ionic bonding

200

Why are enzymes specific to one substrate?

The substrate has a complementary shape to the enzyme’s active site.

200

What is the sugar produced in photosynthesis called?

Glucose

200

In a series circuit, what happens to the current at different points in the circuit?

The current is the same at all points.

300

As you move across Period 3 from left to right, what happens to atomic number?

It increases by one for each element.

300

Name one feature of the lungs that helps gas exchange happen quickly.

Large surface area / thin walls / good blood supply

300

What happens to glucose in a plant after it is made?

It is used for energy and growth and stored as starch

300

State the equation that links voltage, current, and resistance.

V=IR

400

Why is the first ionisation energy of aluminium lower than magnesium?

Aluminium’s outer electron is in a higher energy p-orbital, so it is easier to remove.

400

What happens to enzyme activity after the optimum temperature is passed?

The enzyme denatures and activity decreases rapidly.

400

Explain why photosynthesis slows down in low light conditions.

Because there is less light energy available to drive the reactions. It is a limiting factor. 

400

Explain what happens to the brightness of a bulb if more cells are added to a circuit?

The bulb becomes brighter because the potential difference increases.

500

Explain why both atomic radius decreases and first ionisation energy generally increases across Period 3.


  • Across Period 3, the number of protons increases from left to right, increasing the nuclear charge.
  • Electrons are added to the same energy level, so shielding remains almost the same because no new electron shells are added.
  • The stronger nuclear charge increases the attraction between the nucleus and the outer electrons.
  • This pulls electrons closer to the nucleus, causing the atomic radius to decrease across the period.
  • Because electrons are more strongly attracted to the nucleus, more energy is required to remove an electron.
  • Therefore, ionisation energy increases across Period 3.


500

A student investigates enzyme activity at temperatures from 10°C to 80°C. The reaction rate increases until 40°C, then rapidly decreases. Explain these results in terms of particles, collisions, and enzyme structure.

  • As temperature increases, particles gain kinetic energy and move faster.
  • This causes more frequent successful collisions between enzymes and substrates.
  • Enzyme activity increases up to the optimum temperature.
  • Above about 40°C, bonds holding the enzyme’s shape begin to break.
  • The enzyme becomes denatured and its shape changes.
  • The active site no longer fits the substrate.
  • The reaction rate decreases rapidly.
500

Why are photosynthesis and respiration both important for life on Earth?

Photosynthesis and respiration recycle gases (carbon dioxide and oxygen) and provide energy?

500

A circuit contains a 12 V battery and two 20 Ω resistors connected in series.
Calculate the current in the circuit.

Total resistance = 20Ω+20Ω=40Ω

I = V/R

12/40 = 0.3 A


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