Italy Secondaria di secondo grado – classe 2ª Natural sciences (liceo scientifico)

1. Earth science, biology, chemistry

Earth's motions and surface · Cells and biodiversity · Matter and first chemistry

• 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.
• 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).
• The Particle Model of Matter – All matter is made of tiny particles that are always moving. In a solid they are close and only vibrate; in a liquid they are close but slide past each other; in a gas they are far apart and move fast in all directions. Heating gives particles more energy: either they move faster (temperature rises) or the forces between them are broken (the state changes while the temperature stays the same). Gas pressure comes from particles hitting the walls.