Follow the energy
Science 10 looks like four unrelated subjects bolted together. It is one accounting problem told four times: energy arrives, changes form, does something useful, and ends up as heat.
Why is this one course rather than four?
Because the same law runs through all four units, and Alberta built the course around it rather than around the disciplines.
Unit A is chemical energy: bonds break and form, and the difference shows up as heat or light. Unit B is mechanical energy: work transfers it, efficiency measures how much stayed useful. Unit C is biological energy: photosynthesis stores it in glucose and respiration spends it. Unit D is planetary energy: sunlight arrives, gets redistributed, and radiates back to space.
Four scales — molecules, machines, cells, a planet — and in every one the total is conserved while the useful fraction falls. A student who sees that has one idea to hold rather than four syllabuses, and the questions that join units together stop being surprising.
Where it turns up
- Your electricity bill — measured in kilowatt-hours, which is power times time — an amount of energy
- Why a phone gets warm — the fraction of battery energy that did not become computation
- Why you eat — food is chemical energy, and the label measures it in kilojoules
- Climate — the planet warms when energy in stops matching energy out
- 1. The words, first
- 2. The same story, four times
- 3. The calculations, and why they are the same shape
- 4. Why the useful fraction always falls
- 5. Using this in an answer
The words, first
The idea: Five words that ordinary speech blurs and this course separates.
| Word | What it means |
|---|---|
| Energy | The capacity to do work, measured in joules. Conserved absolutely. |
| Work | A transfer of energy by a force moving something: W = Fd. |
| Power | The rate of transfer: P = W/t, in watts. A watt is a joule per second. |
| Heat | Thermal energy in transit, always from hotter to colder. An object contains thermal energy, not heat. |
| Temperature | The average kinetic energy per particle. A spark at 1000 °C holds far less total energy than a warm bath. |
| Efficiency | Useful output ÷ total input × 100%. Never above 100%. |
| First law | Energy cannot be created or destroyed, only converted. |
| Second law | In every conversion some energy becomes less useful, usually as heat. |
The same story, four times
The idea: Name the input, the useful output and the waste. Every unit in the course fits the same three columns.
| Unit | Energy in | Useful out | Waste |
|---|---|---|---|
| A · Chemical change | Chemical bonds | New bonds, light | Heat |
| B · Technological systems | Fuel or electricity | Motion, light | Heat, sound, friction |
| C · Living systems | Sunlight, then glucose | ATP, growth | Heat |
| D · Global systems | Solar radiation | Weather, currents, life | Infrared to space |
Every row loses its energy the same way. That is the second law, written four times in four vocabularies.
The calculations, and why they are the same shape
The idea: Four formulas, all of them energy equals something times something.
W = Fd · Ep = mgh · Ek = ½mv² · Q = mcΔT · E = Pt
Conservation lets you skip the middle. A 2 kg ball dropped from 5 m has Ep = 2 × 9.8 × 5 = 98 J at the top, so it has about 98 J of kinetic energy just before landing. No motion equations, no time, no acceleration — the totals have to match, so the answer follows.
Efficiency is the same idea used backwards. A motor taking 500 J and delivering 150 J is 30% efficient, and the missing 350 J is not missing — it is heat and sound. Saying where it went, rather than that it was lost, is the habit the course is really testing.
Watch the units. P = W/t needs seconds. Q = mcΔT needs kilograms. Both are silent when wrong, and both are caught by writing the units down and cancelling.
Why the useful fraction always falls
The idea: The first law alone would allow a perfect machine. The second is why there is no such thing, and why every device warms the room.
Conservation is not the same as usefulness. Burn a litre of fuel and every joule is still accounted for afterwards — but most of it is now spread thinly through the air as warmth, and no amount of engineering will gather it back into a form that turns a wheel.
That is what efficiency measures. An incandescent bulb is about 5% efficient at making light and 95% efficient at making heat. Calling it 5% efficient is only true relative to what you wanted.
And why over 100% is impossible. It would require more energy out than in, which is not a design limit that better engineering could beat — it is an accounting identity. A device claiming more is either measuring wrongly or omitting an input.
The planetary version. Earth radiates away roughly what it receives. Greenhouse gases slow the outgoing half, so the surface warms until the books balance again at a higher temperature. Same bookkeeping, different scale.
Using this in an answer
The idea: Questions that look like recall usually reward the connection instead.
“Explain why a car engine is only about 25% efficient.” Chemical energy in fuel becomes heat, expansion, then motion. At each conversion some energy becomes thermal energy spread through the engine block and exhaust, which cannot be recovered as motion. That is the second law, not a fault in the engine.
“Why does a plant need the Sun if matter cycles?” Because matter cycles and energy does not. The carbon goes round indefinitely; the energy enters as light and leaves as heat, so it has to be resupplied.
“Why does melting Arctic ice accelerate warming?” Lower albedo means more absorbed energy, which melts more ice — a positive feedback, meaning self-reinforcing rather than good.
All three are the same answer in different clothes: follow the energy, and say where the unusable part went.