Science & Math Terms, Explained
Textbook definitions manage to be accurate and useless at the same time. These pages take the concepts that come up in chemistry, physics and calculus and explain what they actually mean, why they behave the way they do, and where they show up outside an exam hall. Written for anyone who wants the idea, not just the definition.
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What is a Derivative?
The rate of change at one exact instant — the speedometer to the odometer's total.
What is Entropy?
Why heat spreads, ice melts, and rooms never tidy themselves — counting arrangements, not forces.
What is pH?
The 0–14 acidity scale where every step is ten times — and why blood guards its number.
All 38 terms
What is Activation Energy?
The energy hill every reaction climbs before it starts — and how catalysts shorten it.
What is Continuity?
No jumps, no holes: why some graphs can be drawn without lifting the pen, and what breaks it.
What is a Derivative?
The rate of change at one exact instant — the speedometer to the odometer's total.
What is Electronegativity?
How hard an atom pulls shared electrons — the tug-of-war behind polar bonds and water's powers.
Energy vs power: what's the difference?
Power is the rate, energy is the total. It is why your bill charges kWh and never kW.
What is Entropy?
Why heat spreads, ice melts, and rooms never tidy themselves — counting arrangements, not forces.
Fusion vs fission: what's the difference?
Fission splits heavy atoms apart. Fusion forces light ones together. Both release energy.
What is an Integral?
Adding up endless tiny slices to get a total — distance from speed, area from a curve.
What is Le Chatelier's Principle?
Disturb a balanced reaction and it shifts — settling at a new balance, not the old one.
What is a Limit?
Where a function is heading as it closes in on a point — even when it never arrives.
What is Momentum?
Mass times velocity — the motion an object carries, and why crumple zones save lives.
What is Newton's Third Law?
Every push comes with an equal push back — on a different object, which is why things move.
What is pH?
The 0–14 acidity scale where every step is ten times — and why blood guards its number.
SN1 vs SN2 Reactions: What's the Difference?
One-step shove or leave-then-fill: how crowding on a carbon picks the substitution route.
What is Torque?
Force times distance from the pivot — why long handles beat strong arms.
What is a catalyst?
Speeds up a reaction, survives it untouched, and cannot change how the reaction ends.
What is a half-life?
The time it takes for half of something to disappear, when whatever survives keeps vanishing at the same pace.
What is a log scale?
A chart axis where each step multiplies instead of adds, so 1, 10, 100 sit evenly apart.
What is an atom?
The smallest piece of an element that still counts as that element. Split it and you get something else.
What is DNA?
A long chemical instruction list, written in four letters, copied into nearly every cell.
What is exponential growth?
Growth that multiplies rather than adds, so each round gains more than the one before.
What is force?
A push or a pull between two objects. When several act at once, only the leftover does anything.
What is mRNA?
A short-lived copy of one gene, carried out to where proteins get built, then destroyed.
Mass vs weight: what's the difference?
Mass is what you're made of; weight is how hard gravity pulls on it. Your scale is hiding the difference.
Ionic vs covalent bond: what's the difference?
One atom gives an electron, or two atoms share a pair. That choice decides whether you get salt or water.
Oxidation vs reduction: what's the difference?
Losing electrons is oxidation, gaining them is reduction, and the names point the wrong way.
Vector vs scalar: what's the difference?
A scalar is a size. A vector is a size with a direction. Ask "which way?" and you've sorted it.
What is CRISPR?
Molecular scissors with a postcode: write twenty letters, cut one spot, and the cell does the editing.
Heat vs temperature: what's the difference?
Temperature is how hot. Heat is how much energy moved. A bath beats a cup of tea on the second and loses on the first.
Accuracy vs precision: what's the difference?
Accurate is near the truth. Precise is near each other. The scale that is 20 grams high every time is only one of them.
Endothermic vs exothermic: what's the difference?
An exothermic reaction gives heat out and warms the room. An endothermic one takes heat in and cools it.
Mass number vs atomic number: what's the difference?
Atomic number says which element it is. Mass number says how much mass that one atom has. Carbon-12 and carbon-14 share the first and differ on the second.
Conductor vs insulator: what's the difference?
A conductor lets electricity and heat through; an insulator holds them back. Free electrons are the whole difference.
Distance vs displacement: what's the difference?
Distance is how far you went. Displacement is how far you got, and which way. Twelve miles of winding road between towns 8 miles apart gives 12 of one and 8 of the other.
What is a Leaving Group?
The atom or group that breaks off a molecule and takes the bond's electrons with it. The more stable it is with them, the more readily it goes.
Work vs energy: what's the difference?
Energy is what an object has. Work is energy a force moves into or out of the object. Lifting a box is work; the box on the shelf has the energy.
Nucleophile vs electrophile: what's the difference?
A nucleophile has electrons to offer. An electrophile has room for them. The names describe what each one seeks, not what it holds.
Levers and moments: how do they work?
A lever is a stiff bar on a pivot. A moment is force times distance from that pivot. Push further out and a small push beats a big load.
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