Science you can see
Diffusion: Why Smells Spread
Grades 6–9
concept/mechanism
Science you can see
Verified source
Why does a smell reach you even if you’re across the room? Diffusion is the invisible ‘spreading-out’ of tiny particles, and it happens all around you.
States of Matter: Solid vs Liquid vs Gas
Grades 6–8
concept
Science you can see
Verified source
Same stuff—different behavior. In a solid, particles stay locked in place; in a liquid, they slide; in a gas, they spread out and roam.
Surface Tension: The ‘Skin’ on Water
Grades 6–9
concept/experiment
Science you can see
Verified source
Water can act like it has a thin stretchy skin. That’s surface tension—molecules at the surface pull together more tightly than you’d expect.
Convection: Heat Makes Fluid Circulate
Grades 7–10
process/mechanism
Science you can see
Verified source
Why does hot air rise? Warm fluid becomes less dense and floats upward while cooler fluid sinks—creating a circulating conveyor belt called convection.
Greenhouse Effect: Heat Trapped Like a Blanket
Grades 7–12
concept/limitations
Science you can see
Verified source
Sunlight gets in easily, but some of Earth’s heat has a harder time getting back out. That ‘trapping’ effect is why greenhouse gases matter.
Heat vs Temperature
Grades 6–9
comparison
Science you can see
Verified source
Heat is energy moving from one place to another. Temperature is how fast particles are jiggling on average. Same word in conversation—different idea in science.
Mass vs Weight
Grades 6–9
comparison
Science you can see
Verified source
Mass is how much ‘stuff’ you have. Weight is the gravitational pull on that mass. Same object—same mass everywhere—but weight changes on the Moon.
Reflection vs Refraction
Grades 6–9
comparison
Science you can see
Verified source
A mirror makes light bounce back (reflection). Water makes light bend as it enters (refraction). That’s why a straw looks ‘broken’ at the waterline.
Sound Waves: Frequency vs Amplitude
Grades 6–9
comparison
Science you can see
Verified source
Frequency changes pitch (high vs low). Amplitude changes loudness (quiet vs loud). Same wave—two knobs you can turn.
Density & Buoyancy: Float or Sink
Grades 6–9
concept/mechanism
Science you can see
Verified source
Why do some things float and others sink? It’s a contest between weight pulling down and buoyancy pushing up—and density decides who wins.
Why Salt Melts Ice
Grades 7–10
concept/mechanism
Science you can see
Verified source
Sprinkle salt on ice and it starts melting—even below 0°C. Salt makes it harder for water to freeze into an orderly crystal.
Why Seasons Happen
Grades 6–9
concept/mechanism
Science you can see
Verified source
Seasons aren’t caused by Earth being closer to the Sun. They happen because Earth’s axis is tilted—changing how directly sunlight hits each hemisphere through the year.
Why We See Lightning Before Thunder
Grades 6–9
concept/comparison
Science you can see
Verified source
Lightning and thunder happen at the same time, but light travels much faster than sound—so your eyes get the message first.
Newton’s 3rd Law: Recoil & Reaction
Grades 8–12
concept/mechanism
Science you can see
Verified source
When you push something, it pushes back equally. That’s why rockets work: pushing exhaust backward pushes the rocket forward.
Conservation of Energy: Pendulum Swap
Grades 8–12
concept/mechanism
Science you can see
Verified source
A pendulum trades height for speed and back again. Energy changes form, but the total stays (almost) the same.
Pressure: Why Sharp Knives Cut
Grades 6–10
concept/mechanism
Science you can see
Verified source
Same force, smaller area → bigger pressure. That’s why sharp blades cut and snowshoes don’t sink.
Electromagnetic Induction: Changing Magnet → Current
Grades 9–12
concept/mechanism
Science you can see
Verified source
Move a magnet near a coil and you can generate electricity. The key is change—a changing magnetic field creates an electric push.
Engineering you can see
Momentum vs Impulse
Undergrad intro physics
comparison
Engineering you can see
Verified source
A quick smack and a longer shove can cause the same change in motion. Momentum is what’s moving; impulse is how hard (and how long) you push to change it.
Voltage vs Current
Undergrad intro circuits
comparison
Engineering you can see
Verified source
Voltage is the push. Current is the flow. Resistance decides how much flow you get from a given push.
Series vs Parallel Circuits
Undergrad intro circuits
comparison
Engineering you can see
Verified source
Series is one path. Parallel is many paths. That one wiring choice changes brightness, current split, and what happens when something breaks.
AC vs DC Current
Undergrad intro circuits
comparison
Engineering you can see
Verified source
DC is one direction. AC reverses direction back and forth. That’s why transformers work and why the grid uses AC.
Resonance (Timed Pushes Amplify Motion)
Undergrad intro physics
process/mechanism
Engineering you can see
Verified source
Tiny pushes can build huge motion when the timing matches the system’s natural rhythm. That’s resonance.
Damping (Why Oscillations Die Out)
Undergrad intro physics
process/mechanism
Engineering you can see
Verified source
Vibrations fade because energy leaks away each cycle. That energy loss is damping.
Standing Waves (Nodes & Antinodes)
Undergrad waves
concept/mechanism
Engineering you can see
Verified source
Two waves can lock into a pattern: some points don’t move (nodes), others move most (antinodes). That fixed pattern is a standing wave.
Doppler Effect
Undergrad waves
concept/mechanism
Engineering you can see
Verified source
A moving source makes wavefronts bunch up in front and spread out behind—so the observed frequency shifts. That’s the Doppler effect.
Polarization (Rotating Filters)
Undergrad optics
concept/experiment
Engineering you can see
Verified source
Rotate one polarizing filter in front of another and light fades out. Polarization is about allowed vibration directions.
Thin-Film Interference (Soap Bubble Colors)
Undergrad optics
concept/mechanism
Engineering you can see
Verified source
Soap bubble colors come from interference: reflections from a thin film add or cancel depending on thickness and wavelength.
Undergrad & beyond
Entropy (Microstates Intuition)
Undergrad thermo
concept/mechanism
Undergrad & beyond
Verified source
A gas spreads out because there are far more ways to be spread out than piled in one corner. Entropy tracks how many microscopic arrangements are possible.
Diffusion vs Advection
Undergrad fluids
comparison
Undergrad & beyond
Verified source
Diffusion spreads by random motion. Advection carries material with a bulk flow. Same dye, different transport mechanism.
Laminar vs Turbulent Flow
Undergrad fluids
comparison
Undergrad & beyond
Verified source
Laminar flow is smooth and layered. Turbulent flow swirls and mixes. Increase speed and the flow can flip from calm to chaotic.
Reynolds Number (Intuition)
Undergrad fluids
concept/mechanism
Undergrad & beyond
Verified source
Reynolds number predicts whether flow stays smooth or turns turbulent. It’s the balance of inertia trying to stir things up vs viscosity trying to smooth them out.
Boundary Layer (Flow Near a Surface)
Undergrad fluids
concept/mechanism
Undergrad & beyond
Verified source
Near a surface, fluid ‘sticks’ and slows down. That thin slow region is the boundary layer—and it controls drag and separation.
Lift (Angle of Attack & Airflow)
Undergrad aero
concept/mechanism
Undergrad & beyond
Verified source
Tilt a wing slightly and the airflow bends downward. That momentum change creates an upward force—lift—along with pressure differences around the airfoil.
Feedback Control (PID Intuition)
Undergrad controls
concept/mechanism
Undergrad & beyond
Verified source
A controller constantly compares ‘where you are’ to ‘where you want to be’ and nudges the system back. That loop is feedback control.
Signal vs Noise (SNR Intuition)
Undergrad signals
comparison
Undergrad & beyond
Verified source
A signal is the pattern you care about. Noise is the random junk on top. SNR tells you whether the pattern is still readable.
Fourier Transform (Intuition)
Undergrad signals
concept/mechanism
Undergrad & beyond
Verified source
A complex wave can be built by adding simple sine waves. The Fourier transform tells you which frequencies (and how much) are inside a signal.
Aliasing (Sampling Artifacts)
Undergrad signals
concept/mechanism
Undergrad & beyond
Verified source
Sample a fast pattern too slowly and it can look like a different slower pattern. That illusion is aliasing.
Capacitor: Stores Charge Like a Spring
Undergrad circuits
concept/mechanism
Undergrad & beyond
Verified source
A capacitor stores energy in an electric field. It can soak up charge, then release it—like a spring storing and returning energy.
Random Walk: Why Spread Grows Like √t
Undergrad probability
concept/intuition
Undergrad & beyond
Verified source
Take random steps and you don’t go nowhere—you drift outward slowly. Typical distance from the start grows like the square root of time.
Bayes’ Rule: Test Results Intuition
Undergrad statistics
concept/intuition
Undergrad & beyond
Verified source
A positive test doesn’t always mean you ‘probably have it.’ Bayes updates probability using base rates plus test accuracy.
Gradient Descent: Ball Rolling Down a Hill
Undergrad ML
concept/intuition
Undergrad & beyond
Verified source
To minimize a loss, move in the direction of steepest decrease—like a ball rolling downhill. Step size controls speed vs overshoot.
Little’s Law: Queues (L = λW)
Undergrad systems
concept/intuition
Undergrad & beyond
Verified source
Average items in a system equals arrival rate times average time inside. That’s Little’s Law—and it explains why latency explodes near capacity.
Hashing: Why Collisions Happen
Undergrad CS
concept/mechanism
Undergrad & beyond
Verified source
A hash maps many possible inputs into a limited set of buckets. Eventually two different inputs land in the same bucket—that’s a collision.
Batch vs Streaming Data
Undergrad data
comparison
Undergrad & beyond
Verified source
Batch is like doing laundry once a week; streaming is like washing each dish as soon as you use it. Same goal—different timing.
ETL vs ELT
Undergrad data
comparison
Undergrad & beyond
Verified source
ETL is chopping ingredients before the pot; ELT is dumping everything into the pot first, then cooking and seasoning inside.
Data Lake vs Data Warehouse
Undergrad data
comparison
Undergrad & beyond
Verified source
A data lake is everything poured in as-is. A data warehouse is labeled shelves where everything is organized for fast picking.
Partitioning: Skip What You Don’t Need
Undergrad data
concept/intuition
Undergrad & beyond
Verified source
Partitioning is like a library organized by aisle—if you need ‘History’, you don’t walk every aisle. You jump straight to the right section.
Idempotency: Run Twice, Same Result
Undergrad data
concept/intuition
Undergrad & beyond
Verified source
Idempotency is like pressing an elevator button that lights up once—pressing it again doesn’t call two elevators.
Dedup: Same Record, One Copy
Undergrad data
concept/intuition
Undergrad & beyond
Verified source
Dedup is like stamping identical documents with the same fingerprint—duplicates collapse into one.
Train/Test Split: Don’t Peek
Undergrad ML
concept/intuition
Undergrad & beyond
Verified source
Training on your test data is like studying with an answer key during the exam—you’ll feel great, but you didn’t learn.
Overfitting: Memorizing the Noise
Undergrad ML
concept/intuition
Undergrad & beyond
Verified source
Overfitting is like tracing one exact route to school—one detour and you’re lost. The model memorizes quirks instead of learning the pattern.
Embeddings: Meaning as Coordinates
Undergrad NLP
concept/intuition
Undergrad & beyond
Verified source
Embeddings are like a map of meaning: ‘Paris’ is closer to ‘France’ than to ‘Banana’. Similar things cluster nearby.
RAG: Open-Book LLM (Retrieve Then Write)
GenAI
concept/intuition
Undergrad & beyond
Verified source
RAG is like writing with an open book: first you fetch the right page, then you answer from it.