Part I – Content KnowledgeGeneral ScienceClasses 5–8
General Science (Classes 5–8): Life Processes, Matter, Energy, Electricity and Space
Middle-school science of the Sindh curriculum: classification, micro-organisms, human body systems, ecosystems, elements and compounds, acids and bases, heat, light, sound, electricity and the solar system.
Living things and micro-organisms
- Living things are grouped into kingdoms: animals, plants, fungi, protists and bacteria (monera).
- Vertebrates (with backbone): fish, amphibians, reptiles, birds, mammals.
- Micro-organisms: bacteria, viruses, fungi, protozoa, algae.
- Useful: yeast (bread), bacteria (yoghurt, nitrogen fixation), penicillin from a fungus (Alexander Fleming, 1928).
- Diseases: bacteria – typhoid, cholera, tuberculosis; viruses – polio, measles, flu, dengue; protozoa – malaria (Plasmodium, spread by the female Anopheles mosquito). Dengue is spread by the Aedes mosquito.
- First vaccine (smallpox): Edward Jenner.
Human body systems
- Digestive: mouth → oesophagus → stomach → small intestine (absorption) → large intestine (water absorption). Largest gland: liver (makes bile).
- Respiratory: nose → trachea → bronchi → lungs → alveoli (gas exchange).
- Circulatory: heart has 4 chambers; arteries carry blood away from the heart, veins carry it back. Red blood cells carry oxygen (haemoglobin), white blood cells fight germs, platelets help clotting.
- Excretory: kidneys filter blood; their units are nephrons.
- Nervous: brain, spinal cord, nerves; unit is the neuron.
- Skeletal: adult has 206 bones; smallest bone is the stapes (ear); largest organ is the skin.
- Normal body temperature: 37 °C (98.6 °F).
Plants and ecosystems
- Photosynthesis: carbon dioxide + water → (sunlight, chlorophyll) → glucose + oxygen.
- Respiration: glucose + oxygen → carbon dioxide + water + energy (in all living cells, day and night).
- Flower parts: stamen (male: anther + filament), pistil/carpel (female: stigma, style, ovary).
- Pollination – transfer of pollen to the stigma; fertilisation – fusion of male and female cells.
- Food chain: producer → primary consumer → secondary consumer; decomposers (bacteria, fungi) return nutrients to the soil.
- Ozone layer absorbs harmful ultraviolet rays; it is damaged by CFCs. Excess CO₂ and methane cause the greenhouse effect.
Matter and chemistry
- Element – one kind of atom (O, Fe, Na). Compound – elements chemically combined in a fixed ratio (H₂O, NaCl). Mixture – substances mixed without chemical bonding (air, sea water).
- Atom: protons (+) and neutrons in the nucleus, electrons (–) around it. Atomic number = number of protons.
- Physical change – no new substance (melting ice, dissolving sugar). Chemical change – new substance forms (rusting, burning, cooking).
- Acids turn blue litmus red, pH < 7 (lemon juice, vinegar). Bases turn red litmus blue, pH > 7 (soap, lime water). Acid + base → salt + water (neutralisation).
- Separation: filtration (insoluble solids), evaporation (dissolved salt), distillation (pure water), chromatography (inks).
Heat, light and sound
- Heat travels by conduction (solids), convection (liquids and gases) and radiation (no medium needed – the Sun's heat).
- °F = (9/5 × °C) + 32; water freezes at 0 °C / 32 °F and boils at 100 °C / 212 °F.
- Light travels in straight lines at about 3 × 10⁸ m/s. Reflection – bouncing back (mirrors); refraction – bending when entering another medium (a pencil looks bent in water).
- A prism splits white light into 7 colours (VIBGYOR). Rear-view mirrors of vehicles are convex.
- Sound needs a medium; it travels fastest in solids, slowest in gases (about 340 m/s in air). Pitch depends on frequency, loudness on amplitude.
Electricity, magnetism and force
- Conductors (copper, aluminium) let current flow; insulators (rubber, plastic, wood) do not.
- Units: current – ampere; voltage – volt; resistance – ohm. Ohm's law: V = IR.
- In a series circuit, one bulb going off breaks the whole circuit; in a parallel circuit (home wiring) others stay on.
- An electromagnet is a coil of wire around soft iron carrying current.
- Pressure = force ÷ area (unit pascal). Friction opposes motion.
- Simple machines: lever, pulley, wheel and axle, inclined plane, wedge, screw.
Earth and space
- Planets in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Pluto is now a dwarf planet.
- Mercury – closest to the Sun; Venus – hottest; Mars – red planet; Jupiter – largest; Saturn – famous rings.
- Solar eclipse – the Moon comes between the Sun and the Earth. Lunar eclipse – the Earth comes between the Sun and the Moon.
- The Earth's revolution (365¼ days) and tilted axis cause seasons; rotation (24 hours) causes day and night.
- Layers of the Earth: crust, mantle, outer core, inner core.