SNC1W · Exam review

Science Exam Review

A practice exam with questions from all 5 units, then the key facts from every lesson, unit by unit. For a deeper look at one unit, open its test review.

Unit test reviews

Practice exam

35 questions, the same number from each unit. Each one shows the lesson it comes from.

Unit 1: Questions, Hypotheses and Fair Tests
1
A student tests how the height a ball is dropped from affects how high it bounces. What is the independent variable?
Unit 1: Measurement, Data Tables and Graphs
2
What does the prefix micro (µ) mean?
Unit 1: Research and Scientific Literacy
3
Which source is most reliable for finding out how road salt affects Ontario streams?
Unit 1: The Engineering Design Process
4
In a challenge to build a tower from spaghetti and marshmallows, which is a constraint?
Unit 1: The Engineering Design Process
5
Which of these careers is a skilled trade learned mainly through apprenticeship?
Unit 1: Coding to Model Science
6
Match each coding term to its meaning.
Variable
Loop
List
Comment
Output
Unit 1: Lab Safety and WHMIS
7
Which pictogram has a round border instead of a diamond?
Unit 2: Earth's Spheres and Ecosystem Components
8
Match each sphere to an example that belongs mainly to it.
Atmosphere
Hydrosphere
Lithosphere
Biosphere
Unit 2: Energy Flow: Food Chains, Food Webs and Trophic Levels
9
Put this Ontario lake food chain in order, starting with the producer.
1. 1Zooplankton
2. 2Northern pike
3. 3Yellow perch
4. 4Algae
Unit 2: Photosynthesis and Cellular Respiration
10
A sealed jar holds a potted plant and is kept in complete darkness for two days. What happens to the carbon dioxide level in the jar?
Unit 2: Cycling of Matter: Carbon, Nitrogen and Water Cycles
11
Which of these is acting as a carbon sink?
Unit 2: Biodiversity, Succession and Ecosystem Sustainability
12
Match each indicator to what it tells you.
Many kinds of lichens on trees
Mayfly and stonefly larvae in a stream
Dark, crumbly soil full of earthworms
Frog populations suddenly declining
Unit 2: Human Impacts on Ecosystems
13
A new highway is built through a large forest, splitting it into two halves. Which impact is this?
Unit 2: Climate Change and Ecosystems
14
Lake trout need cold, oxygen-rich water. Why do warmer summers threaten them in many Ontario lakes?
Unit 3: Pure Substances and Mixtures
15
Which of these is a compound?
Unit 3: Physical and Chemical Properties and Changes
16
Which observation is the strongest evidence that a chemical change has happened?
Unit 3: How Models of the Atom Developed
17
How did Chadwick know the particles he found had no charge?
Unit 3: The Periodic Table
18
An element is shiny, can be hammered into a sheet and conducts electricity well. It is most likely a
Unit 3: Patterns in the Periodic Table
19
How many valence electrons does phosphorus (atomic number 15, group 15) have?
valence electrons
Unit 3: Compounds and Chemical Formulas
20
Which compound is ionic?
Unit 3: Chemistry, Consumer Products and Society
21
Which is the best example of a social impact of a product?
Unit 4: Static Electricity
22
A plastic comb becomes negative after you run it through your hair. What happened?
Unit 4: Conductors, Insulators and Grounding
23
You see lightning and hear the thunder 6.0 seconds later. Sound travels about 340 m/s. How far away was the lightning, in kilometres? Give your answer to one decimal place.
km
Unit 4: Current Electricity and Circuits
24
A flashlight has a good battery and a good bulb but does not light. Which is the most likely reason?
Unit 4: Series and Parallel Circuits
25
Three identical bulbs are connected in series to a battery. One bulb burns out. What happens to the other two?
Unit 4: Electrical Energy, Power and Cost
26
Which unit is used on an electricity bill to measure the amount of energy used?
Unit 4: Efficiency and Energy Transformations in Devices
27
Why does an LED bulb cost less to run than an incandescent bulb that gives the same amount of light?
Unit 4: Generating Electricity Sustainably
28
Which best describes a smart grid?
Unit 5: The Sun
29
What process produces the Sun's energy?
Unit 5: How the Sun Drives Earth's Systems
30
Put the steps that produce an aurora in order.
1. 1The energized atoms give off green, red, blue and purple light
2. 2The particles collide with oxygen and nitrogen atoms high in the atmosphere
3. 3Earth's magnetic field guides some particles toward the polar regions
4. 4The Sun releases charged particles in the solar wind or a coronal mass ejection
5. 5The particles travel through space and reach Earth
Unit 5: Moon Phases, Eclipses and Tides
31
The lunar cycle lasts about 29.5 days. About how many days pass between new moon and first quarter? Give your answer to one decimal place.
days
Unit 5: Distances and Scale in Space
32
A light-year is a unit of…
Unit 5: Stars, Galaxies and the Universe
33
Which star colour indicates the hottest surface temperature?
Unit 5: Origin and Evolution of the Universe and Solar System
34
The universe is about 13.8 billion years old and the solar system about 4.6 billion years old. How old was the universe, in billions of years, when the solar system formed?
billion years
Unit 5: Space Exploration and Technology
35
Which of these is a real environmental cost of space exploration?

Key facts by unit

Unit 1: STEM Skills & Investigations

Questions, Hypotheses and Fair Tests

Independent variable: the one thing you change. Dependent variable: what you measure. Controlled variables: everything kept the same.
A hypothesis is a testable possible answer with a reason, often written "If … then … because …".
A control group leaves out the independent variable (or keeps it normal) so you have something to compare against.
Repeated trials and larger samples make results more reliable; average the trials.
Qualitative observations use words; quantitative observations use numbers with units.
Data support or do not support a hypothesis; one experiment does not prove it.

Measurement, Data Tables and Graphs

Prefixes: kilo (k) = 1000, centi (c) = 0.01, milli (m) = 0.001, micro (µ) = 0.000 001 of the base unit.
$1 mL = 1 cm^{3}$ , and $1000 mL = 1 L$ .
Read scales to the smallest marking plus one estimated digit; record all digits on a digital display.
Accuracy = closeness to the accepted value; precision = closeness of repeated measurements to each other.
$percent error = \frac{∣ measured - accepted ∣}{accepted} \times 100%$
Graphs: independent variable on the x-axis, dependent on the y-axis, units on both axes, a title, and a line of best fit for trends.

Research and Scientific Literacy

Judge a source by its author, date, evidence, purpose (bias) and whether it was peer reviewed or agrees with other reliable sources.
A scientific argument has a claim (the answer), evidence (the data) and reasoning (the science idea linking them).
Correlation (changing together) does not show causation (one causes the other); a third factor may cause both.
Peer review means other experts check a study before it is published; it catches many, but not all, errors.
AI tools can be powerful and wrong; check their output against reliable sources.
Two-Eyed Seeing (Elder Albert Marshall) brings together Indigenous and Western ways of knowing.

The Engineering Design Process

Engineering design cycle: define → research → brainstorm → choose and plan → build a prototype → test → evaluate and improve (repeat) → communicate.
Criteria are what the design must do (measurable goals); constraints are the limits (materials, cost, time, size, safety).
A prototype is a first working model built to be tested and improved.
Each round of testing and improving is an iteration; change one thing at a time.
Decision matrix: score × weight for each criterion, then add; the highest total wins.

Coding to Model Science

A variable stores a value; the = sign assigns a value to it.
A for loop repeats the indented lines; range(1, 6) gives 1, 2, 3, 4, 5 (it stops before the second number).
Growing by r% each step means multiplying by $1 + \frac{r}{100}$ each step (10% growth: multiply by 1.1).
Mean = sum of the values ÷ number of values; in Python, sum(values) / len(values).
A model is a simplified version of reality; check it against real data and improve it.

Lab Safety and WHMIS

WHMIS = Workplace Hazardous Materials Information System; updated in 2015 to match the international GHS.
WHMIS has three parts: labels, Safety Data Sheets (SDS) and worker education and training.
Supplier labels show the product identifier, supplier, pictograms, a signal word ("Danger" or "Warning"), hazard and precautionary statements, in English and French.
A workplace label is needed when a product is moved to another container that will be kept (not used right away); it gives the product identifier, safe handling information and a reference to the SDS.
An SDS has 16 sections, including hazards, first aid, spill clean-up, handling and PPE.
Chemical splash in the eye: rinse at the eyewash for at least 15 minutes and get help.

Unit 2: Sustainable Ecosystems & Climate Change

Earth's Spheres and Ecosystem Components

The four spheres are the atmosphere (air), hydrosphere (water), lithosphere (rock and soil) and biosphere (life); they overlap and constantly interact.
Biotic factors are the living parts of an ecosystem; abiotic factors are the non-living parts such as sunlight, temperature, water, soil and pH.
Levels of organization: organism → population (one species) → community (many species) → ecosystem (community + abiotic factors) → biosphere.
A change in one sphere usually causes changes in the others.
Ecosystem services are benefits nature provides, such as clean water, pollination, carbon storage and soil formation.

Energy Flow: Food Chains, Food Webs and Trophic Levels

Producers make their own food (mostly by photosynthesis); consumers eat other organisms; decomposers break down dead matter and recycle nutrients.
Food-chain and food-web arrows point from the food to the eater: the direction energy flows.
Trophic levels: 1st = producers, 2nd = primary consumers, 3rd = secondary consumers, 4th = tertiary consumers.
10% rule: about 10% (roughly 5% to 20%) of the energy at one level is passed to the next; $E_{next} \approx 0.10 \times E_{this}$ .
The rest of the energy is used for life processes such as movement and body heat, lost as heat, or never eaten or digested.
Energy flows one way through an ecosystem and must be constantly resupplied by the Sun; matter is recycled.

Photosynthesis and Cellular Respiration

Photosynthesis: $6 CO_{2} + 6 H_{2} O light C_{6} H_{12} O_{6} + 6 O_{2},$ in chloroplasts, using chlorophyll to absorb light.
Cellular respiration: $C_{6} H_{12} O_{6} + 6 O_{2} \to 6 CO_{2} + 6 H_{2} O + energy,$ in mitochondria.
Photosynthesis stores light energy as chemical energy in glucose; respiration releases it as ATP and heat.
Plants carry out both processes; animals and fungi carry out only respiration.
The products of each process are the reactants of the other, so they are complementary: matter cycles, energy flows through.

Cycling of Matter: Carbon, Nitrogen and Water Cycles

Matter cycles; energy flows. Earth's atoms are reused over and over among the four spheres.
Water cycle: evaporation, transpiration, condensation, precipitation, runoff and infiltration, driven by the Sun and gravity.
Carbon is removed from the air by photosynthesis and returned by respiration, decomposition and combustion; a sink stores more carbon than it releases, a source releases more than it stores.
Nitrogen cycle: fixation (bacteria, lightning) → nitrification (to nitrates) → plant uptake → animals → decomposition → denitrification back to nitrogen gas.
Dynamic equilibrium: inputs and outputs of a reservoir balance, so the amount stays about steady even though matter keeps moving.
Human activity has raised atmospheric carbon dioxide from about 280 ppm before industrialization to over 420 ppm, and greatly increased fixed nitrogen through fertilizer.

Biodiversity, Succession and Ecosystem Sustainability

Biodiversity has three levels: genetic, species and ecosystem diversity; higher biodiversity usually means a more resilient ecosystem.
Population change $= (births + immigration) - (deaths + emigration) .$
Carrying capacity is the largest population an ecosystem can support over the long term; limiting factors such as food, space, disease and predators keep populations near it.
Primary succession starts on bare rock with no soil (pioneer species: lichens, mosses); secondary succession starts where soil remains after a disturbance and is faster.
Indicator species (lichens, frogs, mayfly larvae) reveal air quality, water quality and ecosystem health.
A sustainable ecosystem keeps functioning over the long term in dynamic equilibrium: populations, nutrients and conditions fluctuate around a balance.

Human Impacts on Ecosystems

Habitat loss and fragmentation are the biggest threats to biodiversity; wildlife corridors and protected areas help.
Invasive species spread fast and harm native species because they lack natural predators and diseases in their new home (Ontario examples: zebra mussel, emerald ash borer, purple loosestrife).
Eutrophication: excess nutrients → algal bloom → algae die → decomposers use up dissolved oxygen → fish die (dead zones).
Biomagnification: persistent toxins (mercury, DDT, PCBs) become more concentrated at each higher trophic level, so top predators are most affected.
Overharvesting takes a species faster than it can reproduce (passenger pigeon, northern cod).
Sustainable farming practices include cover crops, crop rotation, no-till, precision agriculture, integrated pest management and vertical farming.

Climate Change and Ecosystems

Climate is the long-term average of weather; climate change is a long-term shift in those patterns.
Human activities (burning fossil fuels, deforestation, livestock, fertilizer, landfills) add carbon dioxide, methane and nitrous oxide, enhancing the greenhouse effect.
Indicators: rising temperatures (Canada roughly 1.7 to 2× the global rate, the North more than 2×, the Arctic nearly 4×), carbon dioxide over 420 ppm, shrinking sea ice and glaciers, thawing permafrost, rising sea level, earlier springs and more extremes.
Ecosystem impacts include range shifts, timing mismatches, warmer lakes, sea-ice loss, more pests and more wildfire.
Indigenous practices such as the Three Sisters, cultural burning and seasonal harvesting reflect an understanding of dynamic equilibrium; Two-Eyed Seeing combines Indigenous and Western knowledge.
Mitigation reduces greenhouse gas emissions or increases sinks; adaptation adjusts to changes that are already happening.

Unit 3: The Nature of Matter

Pure Substances and Mixtures

Matter is anything that has mass and takes up space.
A pure substance has one kind of particle: an element (one kind of atom) or a compound (two or more elements chemically joined in a fixed ratio).
A mixture contains substances physically mixed but not chemically joined; its composition can vary.
A mechanical mixture has visible parts; a solution looks the same throughout.
Mixtures can be separated by physical methods (filtering, evaporating, distilling, magnets); compounds need a chemical reaction.

Physical and Chemical Properties and Changes

A physical property can be observed without making a new substance; a chemical property describes how a substance reacts to form new substances.
Density: $D = \frac{m}{V}$ , usually in g/cm³ or g/mL (1 mL = 1 cm³).
Water has a density of about 1.00 g/mL: less dense objects float, denser objects sink.
A physical change keeps the same substance; a chemical change makes a new substance.
Five clues of a chemical change: new colour, gas formed, precipitate, heat or light, new odour. They are clues, not proof.
On Canadian household products, an octagon frame means the contents are dangerous and a triangle frame means the container is dangerous.

How Models of the Atom Developed

Dalton (1803): atoms are tiny, solid, indivisible spheres; atoms of each element are identical.
Thomson (1897): discovered the electron using cathode rays; plum pudding model.
Rutherford (1911): gold foil experiment showed the atom is mostly empty space with a tiny, dense, positive nucleus.
Bohr (1913): electrons occupy fixed energy levels (shells); explains line spectra.
Chadwick (1932): discovered the neutral neutron in the nucleus.
Modern quantum model: electrons are found in electron clouds (regions of probability) around the nucleus.

Protons, Neutrons, Electrons and Bohr-Rutherford Diagrams

Protons (+1) and neutrons (0) are in the nucleus and each have a relative mass of 1; electrons (−1) are in shells and have almost no mass.
Atomic number = number of protons; it identifies the element.
Neutrons = mass number − atomic number.
In a neutral atom, electrons = protons. Ion charge = protons − electrons.
For elements 1 to 20, shells hold a maximum of 2, 8, 8 and 2 electrons, filled from the inside out.
Isotopes have the same number of protons but different numbers of neutrons.

The Periodic Table

The modern periodic table is arranged in order of increasing atomic number.
A period is a horizontal row (7 periods); a group or family is a vertical column (18 groups).
Metals are left of the staircase line, non-metals to the right, and metalloids along it.
Metals are usually shiny, malleable, ductile and good conductors; non-metals are usually dull, brittle and poor conductors.
Group 1: alkali metals; group 2: alkaline earth metals; group 17: halogens; group 18: noble gases.
Elements in the same group have similar chemical properties.

Patterns in the Periodic Table

Valence electrons are the electrons in the outermost shell; they determine chemical behaviour.
Period number = number of occupied electron shells.
Groups 1 and 2 have 1 and 2 valence electrons; groups 13 to 18 have the group number minus 10 (helium has 2).
Metals lose electrons to form positive ions; non-metals gain electrons to form negative ions, reaching a full outer shell.
Alkali metal reactivity increases down the group; halogen reactivity decreases down the group.
Atoms get bigger down a group and smaller across a period from left to right.

Compounds and Chemical Formulas

A subscript gives the number of atoms of the element just before it; no subscript means 1.
A subscript after a bracket multiplies everything inside; a coefficient multiplies the whole formula.
Ionic compounds: usually a metal and a non-metal; electrons transferred; crystal lattice; high melting point; conduct when dissolved or melted.
Molecular compounds: non-metals only; electrons shared; separate molecules; lower melting points; usually poor conductors.
In an ionic compound the ion charges add to zero, which sets the ratio: $Mg^{2 +}$ and $Cl^{-}$ give $MgCl_{2}$ .

Chemistry, Consumer Products and Society

A product's life cycle: raw material extraction, processing and manufacturing, transport, use, and end of life (reuse, recycling or disposal).
Impacts can be social (people and communities), environmental (air, water, land, living things) or economic (money and jobs).
Household hazardous waste belongs at a hazardous waste depot, not down the drain or in the garbage.
Green chemistry designs products and processes to reduce or eliminate hazardous substances from the start.
Emerging chemical technologies are driven by regulations, costs, scarce resources, consumer demand, health concerns and climate goals.

Unit 4: Principles & Applications of Electricity

Static Electricity

A neutral object has equal numbers of protons (+) and electrons (−). Gaining electrons makes it negative; losing electrons makes it positive.
In solids, only electrons move from object to object. Protons stay locked in the nucleus.
Laws of electric charges: opposite charges attract, like charges repel, and charged objects attract neutral objects.
Charging by contact gives the same sign as the charging object; charging by induction gives the opposite sign.
In the electrostatic series, the material lower in the list gains electrons and becomes negative.
Charge has the symbol $Q$ and is measured in coulombs (C); about $6.24 \times 1 0^{18}$ electrons make 1 C.

Conductors, Insulators and Grounding

Conductors (such as metals) have free electrons that can drift, so charge moves through them easily.
Insulators (such as rubber, glass, plastic and dry wood) hold their electrons tightly, so charge does not move through them easily.
Semiconductors such as silicon conduct a little and are used in chips, LEDs and solar cells.
Grounding connects an object to the Earth, which can give or take electrons, so the object becomes neutral.
Lightning is a huge static discharge between a charged cloud and the ground (or within a cloud); a lightning rod gives it a safe path to the ground.

Current Electricity and Circuits

Current is the rate of flow of charge: $I = \frac{Q}{t}$ , measured in amperes (A); 1 A = 1 C/s.
Potential difference is energy per unit charge: $V = \frac{E}{Q}$ , measured in volts (V); 1 V = 1 J/C.
Resistance $R$ is opposition to current, measured in ohms ( $Ω$ ).
Ammeters go in series (current through); voltmeters go in parallel (potential difference across).
Conventional current flows from + to −; electrons flow from − to +. Diagrams in this unit show conventional current.

Ohm's Law

Ohm's law: $V = I R$ , so $I = \frac{V}{R}$ and $R = \frac{V}{I}$ .
Use volts, amperes and ohms: 1000 mA = 1 A and 1 k $Ω$ = 1000 $Ω$ .
For an ohmic resistor, current is directly proportional to potential difference: double V, double I.
On a graph of V (vertical) against I (horizontal), the slope is the resistance; a steeper line means more resistance.
Lamps, LEDs and diodes are non-ohmic: their resistance changes as the current changes.

Series and Parallel Circuits

Series: one path; $I$ is the same everywhere; $V_{T} = V_{1} + V_{2} + \dots$ ; $R_{T} = R_{1} + R_{2} + \dots$
Parallel: separate branches; $V$ is the same across each branch; $I_{T} = I_{1} + I_{2} + \dots$
Adding a parallel branch decreases the total resistance and increases the total current.
Removing one load in series stops all the current; removing one branch in parallel leaves the others working.
Homes are wired in parallel; switches, fuses and breakers are in series with what they control.

Electrical Energy, Power and Cost

Electricity is the general term for effects of electric charges; electrical energy is the energy carried by moving charges and transformed by loads.
Power is the rate of energy transformation: $P = \frac{E}{t}$ and $P = V I$ , measured in watts (1 W = 1 J/s).
Energy: $E = Pt$ . In joules, use watts and seconds; in kilowatt-hours, use kilowatts and hours.
$1 kWh = 3.6 \times 1 0^{6} J$ ; kW measures power, kWh measures energy.
Cost = energy (kWh) × price per kWh.

Efficiency and Energy Transformations in Devices

Conservation of energy: energy is never created or destroyed, only transformed. Input energy = useful output + wasted energy.
Percent efficiency $= \frac{useful output energy}{total input energy} \times 100% .$
Wasted energy is usually thermal energy (and some sound) that spreads into the surroundings.
In a Sankey diagram, arrow widths are proportional to energy, and the output arrows add up to the input arrow.
LED bulbs are several times more efficient than incandescent bulbs; ENERGY STAR and EnerGuide labels help compare products.

Generating Electricity Sustainably

A generator transforms kinetic energy into electrical energy by spinning a magnet inside coils of wire (electromagnetic induction); a turbine usually does the spinning.
Ontario's electricity is roughly half nuclear and a fifth to a quarter hydroelectric, with natural gas, wind, solar and bioenergy making up the rest; coal was phased out in 2014.
Renewable sources (water, wind, sunlight, regrown biomass) are replaced naturally; non-renewable sources (uranium, natural gas) are not.
Every source has benefits and challenges; storage (batteries, pumped storage) and smart grids help balance supply and demand.
A plan of action: identify the issue, gather data, brainstorm conservation, efficiency and shifting actions, set a measurable goal, act and measure results.

Unit 5: Space Exploration

The Sun

The Sun is a star: a ball of hot plasma, mostly hydrogen and helium, held together by gravity.
Nuclear fusion in the core (about 15 million °C) joins hydrogen nuclei into helium and turns a little mass into a lot of energy.
Layers from the centre out: core, radiative zone, convective zone, photosphere (visible surface, about 5500 °C), chromosphere, corona (over 1 million °C).
Sunspots are cooler, darker regions caused by strong magnetic fields; their number rises and falls in an 11-year cycle.
Flares, CMEs and the solar wind send radiation and charged particles into space and can disrupt satellites, GPS and power grids.
Sunlight travels 1 AU ( $1.496 \times 1 0^{8}$ km) in about 8.3 minutes.

How the Sun Drives Earth's Systems

Earth's axis is tilted about 23.4° and points the same direction in space all year.
Seasons are caused by the tilt, which changes the angle of sunlight and the length of the day. They are not caused by distance: Earth is closest to the Sun in early January.
Noon Sun height at an equinox $= 9 0^{\circ} - latitude$ ; add 23.4° at the June solstice and subtract 23.4° at the December solstice (for places between the Tropic of Cancer and the Arctic Circle, such as southern Canada).
Solstices (about June 21 and December 21) have the longest and shortest days; equinoxes (about March 20 and September 22) have about 12 h of day and night almost everywhere.
Uneven heating by the Sun drives winds, ocean currents and the water cycle.
Auroras form when charged particles from the Sun, guided by Earth's magnetic field, make oxygen and nitrogen in the upper atmosphere glow.

Moon Phases, Eclipses and Tides

The Sun always lights half of the Moon; phases show how much of that lit half faces Earth. One full cycle takes about 29.5 days.
Phase order: new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent.
Solar eclipse: Sun, Moon, Earth in a line, only at new moon. Lunar eclipse: Sun, Earth, Moon in a line, only at full moon.
The Moon's orbit is tilted about 5°, so eclipses happen only a few times a year, not every month.
Two tidal bulges give most coasts two high and two low tides about every 24 h 50 min (high tides about 12 h 25 min apart).
Spring tides (biggest range) occur at new and full moon; neap tides (smallest range) occur at the quarter moons.

The Solar System

Order from the Sun: Mercury, Venus, Earth, Mars, (asteroid belt), Jupiter, Saturn, Uranus, Neptune, (Kuiper belt).
A planet orbits the Sun, is nearly round from its own gravity, and has cleared its orbit. A dwarf planet (like Pluto or Ceres) fails the third rule.
Terrestrial planets are small, rocky, dense and close to the Sun; giant planets are huge, mostly gas or ice, low in density, with many moons and rings.
Asteroids are rocky or metallic; comets are icy and grow a coma and tails that point away from the Sun.
Meteoroid (in space) → meteor (streak of light in the atmosphere) → meteorite (reaches the ground).

Distances and Scale in Space

Scientific notation: $a \times 1 0^{n}$ with $1 \leq a < 10$ . Multiply: add exponents. Divide: subtract exponents.
1 AU = average Earth–Sun distance $= 1.496 \times 1 0^{8}$ km (about 150 million km).
1 light-year = distance light travels in one year $= 9.46 \times 1 0^{12}$ km (about 63 000 AU).
Speed of light $\approx 3.00 \times 1 0^{5}$ km/s; time $= \frac{distance}{speed}$ ; sunlight takes about 8.3 min per AU.
Scale model: model size $=$ real size $\times \frac{model size of reference}{real size of reference},$ using the same factor for every size and distance.

Stars, Galaxies and the Universe

Star colour shows surface temperature: red is coolest, then orange, yellow, white, and blue is hottest.
The H-R diagram plots luminosity against temperature; about 90% of stars lie on the main sequence.
Sun-like star: nebula → protostar → main sequence → red giant → planetary nebula → white dwarf.
Massive star (over about 8 Sun masses): main sequence → red supergiant → supernova → neutron star or black hole.
The more massive a star, the shorter its life.
The Milky Way is a barred spiral galaxy about 100 000 ly across; the Sun is about 26 000 ly from its centre. Galaxy types: spiral, elliptical, irregular.

Origin and Evolution of the Universe and Solar System

Big Bang theory: about 13.8 billion years ago the universe was extremely hot and dense; space has been expanding and cooling ever since.
Redshift: light from distant galaxies is stretched toward red; the farther the galaxy, the bigger the redshift (Hubble's law), so the universe is expanding.
The cosmic microwave background is faint microwave radiation from every direction, about −270 °C: leftover heat from the early universe.
Nebular hypothesis: about 4.6 billion years ago a spinning cloud of gas and dust collapsed into a disc; the Sun formed at the centre and planets formed in the disc.
Rocky planets formed inside the frost line, where it was too hot for ices; giant planets formed beyond it.
Two-Eyed Seeing (Etuaptmumk, from Mi'kmaw Elder Albert Marshall) uses the strengths of Indigenous knowledges and Western science together.

Space Exploration and Technology

Low Earth orbit (about 160 to 2000 km): the ISS at about 400 km orbits in about 92 minutes. Geostationary orbit (35 786 km): one orbit takes 24 h, so the satellite stays over one spot.
The RADARSAT Constellation Mission (three Canadian satellites, 2019) uses radar to see through clouds and darkness, for floods, sea ice, oil spills, ships and crops.
Canadian robotics: Canadarm (space shuttle), Canadarm2 and Dextre (ISS); Canadarm3 is being repurposed for lunar surface work.
Jeremy Hansen flew on Artemis II (April 2026), the first Canadian to travel around the Moon.
A spinoff is a space technology with uses on Earth, such as the neuroArm surgical robot.
Space debris travels at about 28 000 km/h in low orbit; sustainable practices include de-orbiting old satellites and removing debris.