Science 10

Atoms are built from three subatomic particles: protons (positive) and neutrons (neutral) in the nucleus, and electrons (negative) around it.

Position on the periodic table predicts bonding: metals lose electrons and non-metals gain them to form ionic compounds; two non-metals share electrons to form molecular compounds.

Evidence of a chemical change includes an energy or temperature change, a colour or odour change, and the formation of a gas or precipitate.

The atomic model was built from evidence over time — Dalton, Thomson, Rutherford, Bohr — and technologies such as the mass spectrometer and electron microscope let us probe this hidden structure.

Elements combine in fixed ratios set by their charges (ionic) or the atoms actually bonded (molecular) — e.g. $\text{Na}^+$ and $\text{Cl}^-$ give $\text{NaCl}$; $\text{Ca}^{2+}$ and $\text{Cl}^-$ give $\text{CaCl}_2$.

Technologies like the steam engine and Newcomen pump converted heat into useful work by trial and improvement, long before energy was understood as a conserved quantity.

Kinetic energy is the energy of motion; potential energy is energy due to relative position or condition (gravitational $E_p$, and chemical energy stored in fuels and food as a form of potential energy).

Energy is conserved — it is never destroyed, only transformed — so the input energy equals the useful output plus the energy lost (usually as heat).

The concept of energy grew from observing heat and mechanical devices (Rumford, Joule); the laws of thermodynamics were formulated later to EXPLAIN these working machines.

Motion is described with scalar quantities (magnitude only, e.g. distance, speed) and vector quantities (magnitude and direction, e.g. displacement, velocity) — and, without resistive forces, constant-speed motion needs no energy input.

The light microscope revealed that living things are made of cells (the cell theory: all living things are made of cells, cells are the units of life, and cells come from pre-existing cells).

Organelles divide the labour of the cell: the nucleus stores DNA and directs activity, mitochondria release energy, ribosomes build proteins, and the cell membrane controls what enters and leaves.

Multicellular life is organized in levels: specialized cells → tissues → organs → systems, with each level built from the one below and doing a job a single cell could not (which is why organisms above a certain size must be multicellular).

The electron microscope and staining techniques, with far greater magnification and resolution, revealed the organelles inside cells — so understanding advanced as imaging improved.

Plant cells add structures animal cells lack — a cell wall for support and chloroplasts for photosynthesis — so structure and function are complementary.

Earth receives short-wave solar energy and radiates long-wave terrestrial energy back to space; the net radiation budget (input minus output) sets the planet’s temperature.

A biome is a large, open system defined by its climate — mainly temperature and precipitation — and the community of life adapted to it (tropical rainforest, desert, grassland, tundra, taiga).

The greenhouse effect — from gases like carbon dioxide, methane and water vapour — traps some outgoing energy, and that energy flow drives the biosphere on which humans and other species depend.

The same climate produces similar biomes anywhere on Earth, so comparing biomes and their climatographs in different regions reveals the underlying climate pattern.

Net solar energy is uneven across the globe — the equator receives a radiation surplus, the poles a deficit — and this imbalance drives global energy transfer.