Netherlands HAVO 5 (eindexamenjaar) General Natural Science
Chapters: 3
1. Biosphere
Characteristics of the biosphere · Sustainable development
- The Biosphere – The biosphere is the part of Earth where life exists. It is a thin layer where the geosphere (rock and soil), hydrosphere (water) and atmosphere (air) meet, from about 10 km above sea level to about 11 km below it. It is one huge system made of all ecosystems together. Energy flows through it in one direction, from the Sun to plants to animals and out as heat, while matter such as carbon, water and nitrogen goes round in cycles. Living things also change the other spheres: they make oxygen, build soil and store carbon. Humans now change the biosphere strongly, so we must protect it.
- Environment and Sustainable Development – The environment gives us resources, soaks up our waste, supports life and gives beauty. When we take resources faster than nature renews them, or throw waste faster than it can absorb, we cross its carrying capacity and face an environmental crisis. India faces land degradation, air and water pollution, forest and biodiversity loss. Burning fossil fuels traps heat and causes global warming; CFCs thin the ozone layer. Sustainable development meets today's needs without harming the ability of future generations to meet theirs, using clean energy, less waste and traditional knowledge.
2. Matter
Characteristics of matter · Production of materials · Knowledge about matter
- Mixtures and Their Separation – A mixture has two or more substances mixed without any fixed ratio, and each keeps its own properties. Homogeneous mixtures (solutions) look the same everywhere; heterogeneous ones do not. By particle size we get solutions (< 1 nm), colloids (1–1000 nm) and suspensions (> 1000 nm). Colloids scatter light (Tyndall effect). Concentration tells how much solute is in a solution. We separate mixtures by using a difference in their parts: evaporation, crystallisation, distillation, chromatography, sublimation, centrifugation and coagulation.
- Materials and Their Properties – Everything we make is built from materials: wood, metals, plastics, glass, ceramics, fabrics and composites. Each has properties such as strength, stiffness, hardness, flexibility, density, heat and electrical conduction, transparency, water resistance and cost. Designers choose a material whose properties fit the job, think about how it will be shaped and joined (screws, nails, glue, welding, soldering, stitching), and consider safety, cost and the environment. Clothes are made from natural fibres (cotton, wool, silk) and synthetic fibres (polyester, nylon), each with its own feel and use.
- Subatomic Particles and Early Atomic Models – An atom is made of three main particles. Electrons (charge −1, very light) were found with cathode ray tubes. Protons (charge +1, about 1836 times heavier) were found in canal rays. Neutrons (no charge, mass about a proton) were found by Chadwick in 1932. Thomson pictured the atom as a ball of positive charge with electrons stuck in it. Rutherford fired alpha particles at gold foil and found a tiny, heavy, positive nucleus with electrons moving outside. Atomic number Z = number of protons; mass number A = protons + neutrons. Rutherford's model could not explain why atoms are stable or why they give line spectra, which led to Bohr's model.
3. Solar system and universe
Structure of the solar system and universe · Space in daily life · Knowledge about the universe
- The Solar System – The Solar System is the Sun and everything its gravity holds: 8 planets, their moons, dwarf planets, asteroids, comets and dust. The inner four planets (Mercury, Venus, Earth, Mars) are small and rocky. After the asteroid belt come the giants: gas giants Jupiter and Saturn, ice giants Uranus and Neptune. Gravity pulls planets towards the Sun while they move sideways, so they travel in orbits; closer planets move faster and have shorter years. It all formed about 4.6 billion years ago from a spinning cloud of gas and dust.
- Space Exploration – Space exploration means sending rockets, satellites, probes and people beyond Earth's air. Rockets rise by pushing gas down (action–reaction). At about 7.9 km/s sideways a craft keeps falling around Earth in orbit; at 11.2 km/s it escapes. Since 1957 space has been a place of rivalry and cooperation, and it gives us weather forecasts, navigation, communication and new science.
- History of Astronomy: How Our Picture of the Sky Changed – For thousands of years people thought Earth sat still at the centre and the sky turned round it. Careful watching of planets, then the telescope, showed a better picture: Earth and the other planets circle the Sun on ellipses, held by gravity. New ideas won because they explained more and could be tested.