Italy Scuola secondaria di primo grado – classe 3ª Science
Chapters: 3
1. Physics and chemistry
Basic physical quantities · Energy · Chemical changes
- Basic Physical Quantities – A physical quantity is anything we can measure with a number and a unit: speed, volume, weight, density, pressure, temperature, heat and electric charge. Each has a formula or a meter, and each links to everyday things such as floating, a ramp, a thermometer or a bulb in a circuit.
- Work, Energy and Power – Work is done when a force moves an object: W = F × s, measured in joules (J). Energy is the ability to do work. A moving body has kinetic energy ½mv²; a raised body has potential energy mgh. Energy is never made or destroyed, only changed from one form to another. Power is how fast work is done: P = W ÷ t, in watts. Simple machines like levers and pulleys let a small effort move a big load.
- Physical and Chemical Changes – In a physical change, a substance changes its shape, size or state, but no new substance forms; the particles stay the same. In a chemical change, the atoms rearrange to make one or more new substances with new properties. Signs include gas, colour change, heat or light, a precipitate and a new smell. In both kinds, the total mass stays the same.
2. Astronomy and Earth science
Sky and Earth motions · Rocks and Earth structure
- Rotation and Revolution of the Earth – Earth has two main motions. Rotation: it spins on its axis from west to east once in about 24 hours, giving day and night, the daily path of the Sun, local time (15° of longitude per hour) and the bending of winds and currents (Coriolis effect). Revolution: it travels round the Sun on an elliptical orbit once in about 365¼ days. Because the axis is tilted 23.5° from the perpendicular to the orbit plane (the ecliptic) and always points the same way, the overhead Sun moves between the Tropics of Cancer and Capricorn, day length changes, and we get seasons, solstices and equinoxes.
- Rocks and Minerals – A mineral is a natural, non-living solid with a fixed chemical make-up and a regular crystal shape, like quartz or halite. A rock is a mixture of one or more minerals. Rocks are of three types: igneous (from cooled magma or lava), sedimentary (from layers of pressed bits) and metamorphic (changed by heat and pressure). The rock cycle slowly turns each type into the others over millions of years.
3. Biology
Diversity and evolution of living things · Cells and body functions · Heredity · Health and environment
- Diversity and Classification of Living Organisms – Earth has millions of kinds of living things, and India is one of the richest places. To study them, we sort them into groups by asking simple questions about their bodies: Is there a nucleus? One cell or many? Can it make its own food? This gives five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Animals split into invertebrates and vertebrates. Every species gets a two-part scientific name. Viruses are not cells, so they fit in no kingdom.
- The Cell: Basic Unit of Life – Every living thing is made of cells. Robert Hooke first saw cells in cork in 1665. Cells are prokaryotic (no true nucleus, like bacteria) or eukaryotic (true nucleus). Plant cells have a cell wall, chloroplasts and a big vacuole; animal cells do not. Each organelle has a job. Water enters and leaves cells by osmosis. Cells make new cells by mitosis (growth) and meiosis (sex cells).
- Heredity and Mendel's Laws – Heredity is the passing of traits from parents to children through genes. Each parent gives one copy of every gene. A dominant copy hides a recessive one, which is why Mendel saw 3:1 in a monohybrid cross and 9:3:3:1 in a dihybrid cross. Genes are pieces of DNA that make proteins, and proteins build the trait.
- Healthy Lifestyle: Daily Habits That Keep You Well – A healthy lifestyle is a set of daily habits: a balanced diet from five food groups, enough water, 9–11 hours of sleep for school-age children and about 8–10 for teenagers, at least 60 minutes of activity a day, good posture, safe food handling and avoiding tobacco, alcohol and drugs. These habits lower the risk of lifestyle (non-communicable) diseases such as type 2 diabetes, heart disease and some cancers.
- Hygiene and Sanitation – Health means feeling well in body, mind and social life, not just having no disease. We can see health in signs (indicators) like weight for age, energy, sleep and how often we fall ill. Poor food causes malnutrition: under-nutrition (too little food or nutrients) or over-nutrition (too much, leading to obesity). Hygiene means clean habits that stop germs: personal hygiene (body, hands, teeth, clothes), food hygiene (clean, covered, well-cooked food) and environmental hygiene (clean surroundings, covered bins, no still water, toilets). Sanitation means safe disposal of waste and sewage. Drinking water must be made safe by boiling, filtering, chlorine or other methods.