Chemical vs Physical Change

Chemical vs Physical Change

• Chemical properties describe changes that result in new substances. Examples include flammability and corrosiveness.
• Physical properties can be observed without changing a substance into another. Examples include texture, state of matter, and density.

Physical Properties

• State of matter: Solid, liquid, or gas.
• Odour: Smell (sweet, sour, etc.).
• Texture: Surface feel (rough, smooth).
• Lustre: Light reflection (shiny or dull).
• Malleability: Ability to be hammered flat.
• Ductility: Ability to be drawn into wire.
• Brittleness: Tendency to shatter.
• Viscosity: Resistance to flow.
• Hardness: Resistance to scratching.
• Density: Mass per unit volume (D = m/V). Objects with density less than water float; greater than water sink.
• Solubility: Ability to dissolve in water.
• Conductivity: Ability to transfer heat or electricity.

Chemical Properties

• Chemical properties identify a substance's ability to undergo chemical changes, forming new substances.
• Reactivity: How easily a substance reacts with others (e.g., acids, oxygen).
• Stability: Resistance to reactions.
• Corrosivity: Ability to react with oxygen and form new substances.
• Flammability: Ability to react rapidly with oxygen.
• Combustibility: Ability to explode when reacting with oxygen.

Signs of Chemical Change

• Permanent colour change.
• Spontaneous temperature change.
• Smoke, bubbles, or a new gas.
• Light produced (without external heat).
• Formation of a solid (precipitate) when mixing liquids.

Bohr-Rutherford Diagrams

• Protons = Atomic number.
• Neutrons = Mass number - Atomic number.
• Electrons are arranged in orbitals based on periodic table positions.

Patterns/Trends on the Periodic Table

• Atomic radius: Increases down a group due to more energy levels; decreases across a period due to increased nuclear pull. Francium has the largest. Helium the smallest.
• Reactivity (metals): Highly reactive lose electrons easily; larger metals are more reactive.
• Reactivity (non-metals): Highly reactive gain electrons easily; smaller non-metals are more reactive.
• Noble gases: Stable due to full valence shells.

Families on the Periodic Table

• Organized by similar properties and increasing mass.

• Metals: Malleable, lustrous, heat/electricity conductors.

• Metalloids: Possess some metallic properties.

• Alkali metals (Li, Na, K, Rb, Cs, Fr): Highly reactive in water.

• Alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra): Somewhat reactive; react with acids.

• Halogens (F, Cl, Br, I, At): Very reactive; often used as disinfectants.

• Noble gases (He, Ne, Ar, Kr, Xe, Rn): Do not react; stable.

Naming Compounds

• Ionic compounds: Metal + non-metal. Metal name + non-metal name ending in "-ide". (e.g., NaCl = Sodium Chloride). Numerical prefixes are not used.
• Molecular compounds: Non-metal + non-metal. Use prefixes to indicate number of atoms (mono, di, tri, tetra, penta, hexa, hepta, octa). (e.g., CO2 = Carbon dioxide).

Gravity

• An attractive force between any two objects with mass, dependent on mass and distance.

Solar System

• All objects gravitationally bound to the Sun.
• Sun: Star, creates light and heat from nuclear fusion.
• Planets: Orbit the Sun, spherical due to gravity, cleared orbits.
• Dwarf Planets: Similar to planets but have not cleared neighbours from their orbit.
• Moons: Orbit planets; not all planets have moons.
• Astronomical Units (AU): Standard scale inside the Solar System, average Earth-Sun distance.

Red Shift/Blue Shift

• Red Shift: Longer wavelengths due to source moving away. Indicates universe expansion.
• Blue Shift: Shorter wavelengths due to source moving closer

HR Diagrams

• Plots the luminosity and temperature of stars. Stars at top left are larger and hotter. Bottom right are smaller and cooler..

Dark Matter/Dark Energy

• Dark Matter: Undetectable matter needed to explain observed star speeds.
• Dark Energy: Unidentified energy contributing to the accelerating expansion of the universe.

Big Bang

• 13.5 billion years ago, rapid expansion from a tiny point.
• Evidence: Expanding universe; early chemical composition; oldest star characteristics; Cosmic Microwave Background Radiation (CMB) – leftover heat from the hot early universe.

Asteroids, Meteoroids, Meteors, Meteorites

• Asteroids: Rocky objects orbiting the Sun.
• Meteoroids: Small asteroids near Earth's orbit.
• Meteors: Meteoroids entering Earth's atmosphere (shooting stars).
• Meteorites: Meteors that reach the ground.

Comets

• Frozen gas chunks with long orbits around the sun. Form tails when near the sun that point away from it.

Eclipses

• Solar eclipse: Sun → Moon → Earth.
• Lunar eclipse: Sun → Earth → Moon.
• Occurs only when positions align; lunar eclipses more common visible from large area..

Electricity

Law of Electric Charges

• Like charges repel; opposite charges attract.

Activity Series

• Neutral objects have equal positive and negative charges.
• Positively charged objects have more positive charges.
• Negatively charged objects have excess negative charges.

Applications of Static Electricity

• Lightning: Static discharge.
• Electronic Manufacturing: Grounding to prevent damage.
• Photocopiers: Static electricity attracts toner particles to paper.
• Air filters: Static charges collect particles.

Ohm's Law

• Charge (Q): Unit Coulomb (C). Amount of excess electrons or protons (1 e/p 1.6 x 10-19 C).
• Voltage (V): Unit Volts (V). Energy a charge gets or loses (1 V = 1 Joule/Coulomb).
• Current (I): Unit Amperes (A). Amount of charge passing a point per second (1 A = 1 Coulomb/second).
• Resistance (R): Unit Ohms (Ω). Difficulty for electricity to flow through a material.
• Relationship: Voltage increases, current increases; resistance increases, current decreases.

Charging by Friction/Contact

• Friction: Rubbing transfers electrons, creating opposite charges.
• Contact: Directly transferring electrons from one object to another.

Insulators/Conductors

• Conductor: Material allows electrons to flow easily (e.g., metal).
• Insulator: Material resists electron flow (e.g., rubber, plastic).

Series/Parallel Circuits

• Series: Components in a line; same current flows through each.
• Parallel: Components have own branches; same voltage across each.

Power and Cost

• Power (P): Rate of energy use (Watts (W), Joules/second).
• Energy: Power x time. (Joules, Kilo Watt Hours)
• Cost: Rate x Energy.

Trophic Levels

• Producers (autotrophs): Make their own food (e.g., plants).
• Consumers (heterotrophs): Get energy by consuming other organisms.
• Primary consumers: Consume producers.
• Secondary consumers: Consume primary consumers.
• Tertiary consumers: Consume secondary consumers.
• Energy transfer efficiencies average about 10% between trophic levels.

Energy in Ecosystems

• Energy flows from producers to consumers.
• Photosynthesis: Converts sunlight into chemical energy (sugar). CO2 + H2O → O2 + Sugar.
• Cellular Respiration: Releases energy from sugars (sugar + O2 → H2O + CO2 + Energy)

Food Chains/Food Webs

• Food chains: Single pathways of energy transfer.
• Food webs: Complex networks of interconnected food chains.

Population Growth Curves

• Lag phase: Slow population growth.
• Exponential growth phase: Rapid population growth.
• Plateau phase: Population stabilizes near carrying capacity.

Biotic/Abiotic Factors

• Biotic: Living or once-living components (e.g., animals, plants, dead leaves).
• Abiotic: Non-living components (e.g., water, air, sunlight, rocks).

Ecological Pyramids

1. Pyramid of Numbers: Depicts number of individuals at each trophic level. May be inverted.
2. Pyramid of Biomass: Depicts total mass of individuals at each trophic level. May be inverted.
3. Pyramid of Energy: Depicts energy transferred at each trophic level; always wider at base.

Predator/Prey

• Predator: Eats prey.
• Prey: Eaten by predator.

Symbiotic Relationships

• Mutualism: Both species benefit.
• Commensalism: One species benefits, the other is unaffected.
• Parasitism: One species benefits, the other is harmed.