Class 4 General Science
Explore particles, states of matter, mixtures, solutions, physical and chemical changes, temperature, heat, forces, energy, light, sound, magnetism, electricity, Earth science and controlled experiments through 30 progressive General Science lessons.
⚛️ Matter, Particles and Changes
Understanding Particles in Matter
A useful scientific model describes matter as being made of extremely small particles. These particles are too small to see individually with our eyes and are always moving.
Solid → Particles remain close and vibrate around positions
Liquid → Particles remain close but move past one another
Gas → Particles are much farther apart and move freely
Use small beads or dots on paper to create simple particle models of a solid, liquid and gas.
Particle drawings are models that help us explain matter. They are not life-size pictures of actual particles.
Comparing the Three States of Matter
Solids, liquids and gases have different observable properties. We can compare whether they keep their shape and volume and how easily they flow.
Solid: Fixed shape and volume
Liquid: Fixed volume but takes container shape
Gas: No fixed shape or fixed volume; spreads to fill available space
Create a three-column table and classify familiar examples as solids, liquids or gases.
The state of a substance can change when conditions such as temperature or pressure change.
Understanding Changes of State
Matter can change from one state to another when energy is transferred. Common changes include melting, freezing, evaporation and condensation.
Solid → Liquid = Melting
Liquid → Solid = Freezing
Liquid → Gas = Vaporisation
Gas → Liquid = Condensation
Draw arrows between solid, liquid and gas and label the changes of state you have learned.
During a change of state, the substance may remain the same chemical substance even though its physical state changes.
Investigating Melting and Freezing Points
The melting point is the temperature at which a solid changes to a liquid under specified conditions. The freezing point is the temperature at which a liquid changes to a solid.
Pure water freezes and ice melts at about 0°C under ordinary atmospheric pressure.
With teacher supervision, observe ice melting and record temperature readings using a suitable thermometer.
Different substances can have different melting and freezing points.
🧪 Mixtures, Solutions and Changes
Understanding Mixtures
A mixture contains two or more substances physically combined. The substances in a mixture have not necessarily formed a new chemical substance.
Sand + stones
Salt + water
Mixed dry grains
Create a safe dry mixture using teacher-approved materials and identify its different components.
Mixtures can often be separated by using differences in the properties of their components.
Exploring Methods of Separation
Different mixtures require different separation methods. Scientists choose a method according to properties such as particle size, solubility or magnetic behaviour.
Handpicking • Sieving • Filtration • Settling and decanting • Magnetic separation
Choose an appropriate method for separating sand from water, large stones from sand and iron objects from non-magnetic materials.
There is no single separation method that works for every mixture.
Understanding Solutions
A solution is a homogeneous mixture in which one or more substances are dissolved in another substance.
Salt = Solute
Water = Solvent
Salt dissolved in water = Solution
With teacher supervision, dissolve a small measured amount of salt in clean water and observe the mixture.
When a substance dissolves, it has not simply vanished. Its particles are dispersed through the solution.
Investigating Solubility
Solubility describes how much of a substance can dissolve in a particular solvent under specified conditions. Different substances have different solubilities.
Salt dissolves substantially in water.
Sand has very low solubility in water.
Add equal small amounts of teacher-approved substances to equal amounts of water and compare what happens after stirring.
Temperature and the type of solute and solvent can affect solubility.
Distinguishing Reversible and Irreversible Changes
A reversible change can be reversed so that the original material or condition can be recovered relatively easily. An irreversible change cannot easily be reversed to restore the original materials.
Melting and refreezing ice → Reversible physical change
Cooking an egg → Not easily reversible
Classify several everyday changes as reversible or irreversible and explain your reasoning.
Reversible/irreversible and physical/chemical are related ideas, but they are not exactly the same classification.
Introduction to Physical Changes
A physical change alters a physical property such as size, shape or state without producing a different chemical substance.
Melting ice • Cutting paper • Dissolving salt in water
Identify the physical property that changes in several everyday examples.
A physical change does not necessarily mean the change is easy to reverse.
Introduction to Chemical Changes
A chemical change produces one or more new substances with different chemical properties. Chemical changes are often difficult to reverse by simple physical means.
Rusting iron • Burning material • Cooking food
Look at teacher-provided pictures of changes and discuss which may involve formation of new substances.
Do not burn substances or mix unknown chemicals for classroom experiments unless the activity is professionally supervised.
🌡️ Temperature and Heat
Measuring Temperature
Temperature describes how hot or cold something is and can be measured using a thermometer. Degrees Celsius (°C) is a commonly used temperature unit.
Ice-water mixture → Near 0°C under suitable conditions
Normal room temperature → Often around 20–30°C depending on place and season
With teacher supervision, use a safe classroom thermometer to compare the temperatures of appropriate samples.
Never use touch alone to measure temperature accurately.
Understanding Heat Transfer
Thermal energy naturally transfers from a region at higher temperature toward a region at lower temperature until the temperatures become closer to equilibrium.
Place a cool metal spoon in warm water → Energy transfers between the warmer water and cooler spoon.
Why does an ice cube become warmer and melt when left in a warmer room?
Temperature and thermal energy are related but are not identical concepts.
Exploring Thermal Conductors
Thermal conductors allow thermal energy to transfer through them relatively easily. Many metals are good thermal conductors.
Copper • Aluminium • Iron
Examine pictures of cooking utensils and identify where metals are used to transfer heat.
Never touch heated metal to test whether it conducts heat.
Exploring Thermal Insulators
Thermal insulators reduce the rate at which thermal energy passes through them. Materials such as foam, wool, wood and some plastics can act as useful thermal insulators.
An insulated bottle helps reduce thermal energy transfer between its contents and surroundings.
Identify insulating materials used in lunch boxes, oven gloves and insulated containers.
An insulator slows heat transfer; it does not permanently stop all thermal energy transfer.
⚙️ Forces, Work and Energy
Understanding Contact and Non-Contact Forces
Contact forces act when objects interact through physical contact. Non-contact forces can act across a distance without the objects directly touching.
Non-Contact: Gravity • Magnetic force
Classify everyday examples as contact or non-contact forces.
A force can act even when two objects are not touching.
Investigating Gravitational Force
Gravity is an attractive force between masses. Earth’s large mass produces the gravitational attraction that gives objects weight near Earth’s surface and causes unsupported objects to accelerate downward.
Release a ball → Earth’s gravitational force accelerates it downward.
Safely release two suitable lightweight objects from the same low height and observe their downward motion.
Gravity is a non-contact force.
Investigating the Effects of Friction
Friction acts between surfaces in contact and opposes their relative motion. It can slow moving objects, produce heating and provide useful grip.
Shoes gripping the ground • Bicycle brakes • Writing with a pencil
Move the same object over different surfaces using similar conditions and compare its movement.
Friction is not always unwanted. Many everyday activities depend on it.
Understanding Work in Science
In physics, work is done by a force when the force causes displacement and has a component in the direction of that displacement. This scientific meaning is more specific than the everyday word “work.”
Push a box and make it move in the direction of the push → The force does work on the box.
Compare pushing a box that moves with pushing a wall that does not move. Which example involves mechanical work on the object?
Using effort does not always mean mechanical work is being done on an object in the physics sense.
Exploring Different Forms of Energy
Energy can be stored or transferred in different ways. At this level, we can recognise forms or stores associated with motion, position, chemicals, heating, light, sound and electricity.
Moving bicycle → Kinetic energy
Raised object → Gravitational potential energy
Battery → Chemical energy store
Sunlight → Transfers energy by radiation
Identify energy changes in a torch, moving toy and ringing bell.
Energy can be transferred and transformed; it is not created from nothing by a device.
💡 Light and 🔊 Sound
Understanding Reflection of Light
Reflection happens when light reaches a surface and changes direction. Smooth surfaces such as mirrors can produce clear reflections.
For a simple mirror, the angle at which a light ray arrives equals the angle at which it reflects, measured from an imaginary line perpendicular to the surface.
Observe reflections in a safe mirror from several positions.
Never reflect sunlight or powerful light sources into anyone’s eyes.
Exploring the Formation of Images
A plane mirror forms an image because reflected light enters our eyes and appears to come from behind the mirror. The image in a plane mirror is upright and appears the same size as the object.
Upright • Same apparent size • Appears behind the mirror
Place a safe object in front of a plane mirror and observe the object’s image.
The image in a plane mirror is virtual—it cannot be projected onto a screen in the way a real image can.
Understanding Pitch and Loudness
Pitch describes how high or low a sound seems and is mainly related to vibration frequency. Loudness relates to how strongly we perceive a sound and is influenced by the amplitude of the sound wave, distance and other factors.
Faster vibration → Generally higher pitch
Greater vibration amplitude → Generally greater sound intensity
Listen to safe sound examples and classify differences in pitch separately from differences in loudness.
Pitch and loudness describe different properties of sound.
Exploring Sound Transmission Through Materials
Sound is a mechanical wave and requires matter through which to travel. It can travel through solids, liquids and gases because their particles can transmit vibrations.
Solid → String
Liquid → Water
Gas → Air
Use a teacher-supervised cup-and-string telephone to investigate how vibrations travel through a stretched string.
Sound cannot travel through a perfect vacuum because there are no particles there to transmit the mechanical vibration.
🧲 Magnetism and ⚡ Electricity
Understanding Magnetic Fields
A magnetic field is the region around a magnet in which magnetic forces can act. The field has both strength and direction.
A compass placed at different positions around a bar magnet can point in different directions because of the magnetic field.
With teacher supervision, place small compasses around a bar magnet and sketch the directions they point.
We cannot see a magnetic field directly, but we can observe its effects.
Introduction to Electric Circuits
An electric circuit is a path through which electric current can flow. A simple circuit can contain a cell or battery, conducting wires and a device such as a small lamp.
Cell/Battery → Wires → Lamp → Complete conducting path
Identify the source, connecting wires and output device in a teacher-provided low-voltage circuit diagram.
A simple lamp normally lights only when there is a complete conducting path through the circuit.
Building a Simple Electric Circuit
A simple low-voltage circuit can be built using a battery or cell, suitable wires and a small compatible lamp. Correct connections create a closed path for electric current.
Connect cell → wire → lamp → wire → back to cell.
Using only classroom low-voltage components, build a simple circuit and test whether the lamp lights.
Use only teacher-approved low-voltage batteries. Never connect classroom experiments to wall sockets or household mains electricity.
Understanding Electrical Conductors and Insulators
Electrical conductors allow electric current to flow relatively easily. Electrical insulators strongly resist current flow. Many metals are good conductors, while materials such as plastic and rubber are commonly used as insulators.
Copper → Good conductor
Plastic → Good insulator under ordinary conditions
Rubber → Common insulating material
Using only a teacher-supervised low-voltage circuit, test approved objects to determine whether they complete the circuit.
Never test household electricity, sockets, electrical appliances or unknown liquids for conductivity.
🌍 Exploring Planet Earth
Exploring Earth’s Internal Structure
Earth is made of layers with different compositions and physical properties. A simple model divides Earth into the crust, mantle and core, while scientists often divide the core into outer and inner parts.
Crust → Thin outer rocky layer
Mantle → Thick layer beneath the crust
Outer Core → Mainly liquid iron and nickel
Inner Core → Mainly solid iron and nickel
Draw a cross-section of Earth and label the crust, mantle, outer core and inner core.
Scientists learn about Earth’s deep interior mainly through indirect evidence, especially seismic waves, rather than by travelling to the core.
🔬 Scientific Investigation
Designing a Controlled Science Experiment
A controlled experiment is designed so that the effect of one chosen factor can be investigated while other important conditions are kept as consistent as possible.
Does water temperature affect how quickly sugar dissolves?
Independent variable: Water temperature
Dependent variable: Time taken to dissolve
Controlled variables: Amount of water, amount of sugar, container size and stirring method
1. Ask a testable question.
2. Research or consider what you already know.
3. Make a prediction.
4. Identify what you will change.
5. Decide what you will measure.
6. Keep other important conditions controlled.
7. Follow a safe procedure.
8. Record observations and measurements.
9. Repeat trials when appropriate.
10. Compare results and draw an evidence-based conclusion.
A good scientific conclusion is based on the evidence collected, not on whether the original prediction was correct.