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Form 3 Integrated Science Recap | Joe (2026)

Form 3 Integrated Science

Integrated Science

Joe (2026)

For use on Saturday, 5 September 2026

01

Light

Laws of Reflection

A narrow ray of light strikes a horizontal plane mirror at point O. The angle between the incident ray and the surface of the mirror is 35°. A normal is drawn at O.

Incident ray Reflected ray Normal O 35° Plane mirror

The diagram is not drawn to scale.

  1. State the two laws of reflection.
  2. Define the normal at the point of incidence.
  3. Calculate the angle of incidence.
  4. Determine the angle of reflection.
  5. Calculate the angle between the incident ray and the reflected ray.
  6. A student states that the angle of incidence is 35°. Explain the mistake made by the student.
9 marks
02

Matter

Elements, Mixtures and Compounds

A teacher shows Joe five samples. Information about the particles or substances in the samples is given in the table.

Sample Description
P Contains only iron atoms.
Q Contains iron particles and sulfur particles mixed together without heating.
R Contains only particles made of iron and sulfur atoms chemically joined in a fixed ratio.
S Contains oxygen and nitrogen gases that are not chemically joined together.
T Contains only water molecules, each made of hydrogen and oxygen atoms chemically joined together.
  1. Classify each of P, Q, R, S and T as an element, a mixture or a compound.
  2. State what is meant by an element.
  3. State what is meant by a compound.
  4. Give two differences between a mixture and a compound.
  5. Describe how iron can be separated from sample Q.
  6. Joe tries to separate the iron from sample R using the same method. Explain why this method does not work.
  7. When iron and sulfur are heated strongly, iron sulfide is formed. State one observation or test that could show that a new substance has been formed.
13 marks
03

Scientific Investigation

Independent, Dependent and Controlled Variables

Joe investigates how the height from which a ball is released affects its first rebound height. He releases the same rubber ball from different heights onto the same hard floor. The ball is released without being pushed, and its first rebound height is measured using a vertical metre rule.

Release height / cm First rebound height / cm
40 25
60 38
80 51
100 64
120 77
  1. Identify the independent variable in this investigation.
  2. Identify the dependent variable in this investigation.
  3. State three controlled variables in this investigation.
  4. Explain why Joe should use the same ball throughout the investigation.
  5. Write a suitable hypothesis for the investigation.
  6. Describe the relationship shown by the results in the table.
  7. Suggest why Joe should repeat the measurement at each release height.
  8. State one precaution that can improve the accuracy of the rebound-height measurements.
12 marks
04

Living Things

Seven Characteristics of Organisms

Scientists use seven life processes to describe the characteristics of living organisms. The observations below were made while studying a young plant and a small animal.

Observation Description
A The shoot bends and grows towards a light source.
B The animal takes in food and digests it.
C Energy is released from food inside living cells.
D The animal removes carbon dioxide and urea from its body.
E The plant becomes taller and develops more leaves.
F The animal moves away when it is touched.
G Adult organisms produce offspring of the same species.
  1. Name all seven characteristics of living organisms.
  2. Match each observation A–G to the most suitable characteristic of living organisms.
  3. Explain the difference between sensitivity and movement, using one observation from the table.
  4. Explain why respiration is not the same as breathing.
  5. State what is meant by excretion.
  6. Explain why removing undigested food from the body is not usually classified as excretion.
  7. A dormant seed does not show obvious movement or growth. Explain why it may still be classified as living.
16 marks

Question 1

  1. The two laws of reflection are:
    • The angle of incidence is equal to the angle of reflection.
    • The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
  2. The normal is an imaginary line drawn perpendicular to the reflecting surface at the point where the incident ray strikes the surface.
  3. Angles of incidence and reflection are measured from the normal, not from the mirror surface.
    Angle of incidence
    = 90° − 35°
    = 55°
  4. According to the law of reflection:
    Angle of reflection = angle of incidence
    = 55°
  5. The normal lies between the incident and reflected rays.
    Angle between the two rays
    = 55° + 55°
    = 110°
  6. The student has measured the angle between the incident ray and the mirror surface. The angle of incidence must be measured between the incident ray and the normal. Therefore, the angle of incidence is 55°, not 35°.
Remember: The angle between a ray and the mirror surface is not the angle of incidence or reflection. Both angles are always measured from the normal.

Question 2

    • P contains only iron atoms: element.
    • Q contains iron and sulfur that are not chemically joined: mixture.
    • R contains iron and sulfur chemically joined in a fixed ratio: compound.
    • S contains oxygen and nitrogen gases that are not chemically joined: mixture.
    • T contains only water molecules: compound.
  2. An element is a pure substance containing only one type of atom. It cannot be broken down into simpler substances by chemical methods.
  3. A compound is a pure substance formed when atoms of two or more different elements are chemically joined together in a fixed ratio.
  4. Any two suitable differences:
    • In a mixture, the substances are not chemically joined; in a compound, the elements are chemically joined.
    • The components of a mixture can usually be separated by physical methods; the elements in a compound require chemical methods to separate them.
    • The substances in a mixture may be present in different proportions; the elements in a compound are present in a fixed ratio.
    • The components of a mixture usually keep many of their own properties, while a compound has properties different from those of its elements.
  5. Move a magnet over or through sample Q. The iron is attracted to the magnet, while the sulfur is not. The iron can therefore be removed by magnetic separation.
  6. In sample R, the iron atoms are chemically joined to sulfur atoms in iron sulfide. The iron is no longer present as separate iron particles and cannot be pulled out by a magnet.
  7. Suitable evidence includes:
    • the product has a different colour or appearance;
    • the product has properties different from iron and sulfur;
    • the iron can no longer be separated using a magnet;
    • energy is released or absorbed during the reaction.
    For example, the product is a dark solid and the original iron particles can no longer be removed with a magnet.
Element: one type of atom.
Compound: different elements chemically joined in a fixed ratio.
Mixture: substances together without being chemically joined.

Question 3

  1. The independent variable is the release height of the ball. This is the variable deliberately changed by Joe.
  2. The dependent variable is the first rebound height of the ball. This is the variable measured in response to the change in release height.
  3. Any three:
    • the ball used;
    • the surface or floor;
    • the method of releasing the ball;
    • the ball must be released without being pushed;
    • the measuring instrument or method;
    • the position and orientation of the metre rule.
  4. Different balls may have different masses, materials, sizes or elasticities. These differences can affect rebound height. Using the same ball ensures that any change in rebound height is mainly caused by the change in release height.
  5. A suitable hypothesis is: If the release height of the ball increases, its first rebound height will increase.
  6. The results show that the first rebound height increases as the release height increases. The increases are approximately proportional over the range tested. For example, a release height of 40 cm gives a rebound height of 25 cm, while a release height of 120 cm gives a rebound height of 77 cm.
  7. Repeating each measurement allows Joe to:
    • identify anomalous results;
    • calculate a mean rebound height;
    • reduce the effect of random errors and make the result more reliable.
  8. Any suitable precaution, for example:
    • place the metre rule vertically and close to the path of the ball;
    • read the scale at eye level to reduce parallax error;
    • use a video recording or slow-motion camera to identify the maximum rebound height;
    • release the ball without adding a downward force;
    • measure from the same point on the ball each time.
Independent variable: deliberately changed.
Dependent variable: measured or observed.
Controlled variables: kept constant to make the investigation a fair test.

Question 4

  1. The seven characteristics of living organisms are:
    • Movement
    • Respiration
    • Sensitivity
    • Growth
    • Reproduction
    • Excretion
    • Nutrition
    These can be remembered using the mnemonic MRS GREN.
    • A — the shoot grows towards light: sensitivity.
    • B — the animal takes in and digests food: nutrition.
    • C — energy is released from food: respiration.
    • D — carbon dioxide and urea are removed: excretion.
    • E — the plant becomes taller and develops more leaves: growth.
    • F — the animal moves away when touched: movement and also demonstrates sensitivity.
    • G — adults produce offspring: reproduction.
  3. Sensitivity is the ability to detect a change or stimulus and make a response. Movement is a change in the position of the whole organism or part of the organism. In observation F, touch is the stimulus. Detecting the touch and responding to it shows sensitivity, while moving away is the movement produced as part of the response.
  4. Respiration is the chemical process in living cells that releases energy from food. Breathing is the physical movement of air into and out of the lungs. Breathing helps supply oxygen for respiration, but the two processes are not the same. Plants and microorganisms also respire even though they do not breathe using lungs.
  5. Excretion is the removal from an organism of toxic materials, waste products of metabolism and substances in excess of requirements. Examples include carbon dioxide and urea.
  6. Undigested food has not been absorbed into cells and has not been produced by metabolic reactions. Its removal is called egestion, not excretion. Excretion specifically involves removing metabolic waste or substances in excess from the body.
  7. A dormant seed may carry out its life processes at a very slow rate. It contains living cells and may still respire slowly. When suitable conditions such as water, oxygen and an appropriate temperature are provided, it can germinate, grow and show other life processes. Therefore, the absence of obvious movement or growth at one moment does not prove that it is non-living.
MRS GREN
Movement · Respiration · Sensitivity · Growth · Reproduction · Excretion · Nutrition
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