OpenStem

@openstem · Joined Jul 2026

7420 public items8 groups

Note~189 words · 1 min

Temperature is a number for hot and cold Hot cocoa has a high temperature. An ice cube has a low one. A thermometer measures it, which is how a doctor checks for a fever and a cook checks if dinner is ready. Heat only moves one way Heat alw

Physics

Physics · L1 · Heat & Temperature

@openstem

Note~163 words · 1 min

A battery pushes electricity round a loop A battery is a small store of energy. It has two ends called terminals, and electricity needs a path out of one, all the way round, and back into the other. One gap and nothing works A switch is tha

Physics

Physics · L1 · Batteries & Simple Circuits

@openstem

Note~221 words · 1 min

The invisible pull Gravity is a force you can't see but feel constantly. Earth pulls everything near it downward: you, your toys, raindrops, even the air. Let go of something with nothing holding it up and it falls. Not sideways, not upward

Physics

Physics · L1 · Gravity & Falling

@openstem

Note~270 words · 1 min

Light can bounce Light travels in straight lines, but it can also bounce off things, like a ball off a wall. That bouncing is reflection. Some surfaces bounce light far better than others, which is why you see yourself clearly in a mirror a

Physics

Physics · L1 · Mirrors & Reflections

@openstem

Note~237 words · 1 min

It isn't about weight A steel ship weighs as much as hundreds of elephants and floats. A small stone weighs almost nothing by comparison and sinks straight down. What dense means Dense means tightly packed for its size: heavy for how small

Physics

Physics · L1 · Floating & Density

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Note~228 words · 1 min

Every sound starts with something shaking A drum skin, a guitar string, your vocal cords, a speaker cone. Something vibrates, and two separate things about that vibration decide what you hear. Loud or quiet Hit a drum hard and the skin shak

Physics

Physics · L1 · Sound & Music

@openstem

Note~242 words · 1 min

Everything around you is matter A rock, a glass of juice, the air you breathe: all matter, meaning all of it takes up space. But they don't behave the same way, and they sort into three everyday kinds. Quick test: stays in one shape, it's a

Physics

Physics · L1 · Solids, Liquids & Gases

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Note~202 words · 1 min

Your shadow changes all day Check your shadow in the morning, at lunchtime, and before dinner. It won't look the same. Sometimes it stretches out long, sometimes it shrinks right down. That's because the Sun doesn't stay put. It appears low

Physics

Physics · L1 · Shadows Through the Day

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Note~307 words · 2 min

Different shapes, same strong ends Magnets come as straight bars, bent horseshoes, and rings like a donut. Whatever the shape, the pull is always strongest at the two ends, called the poles. The middle barely pulls at all. A horseshoe magne

Physics

Physics · L1 · Magnets: A Closer Look

@openstem

Note~238 words · 1 min

What makes a machine "simple" Not a robot and not a motor. A simple machine is just a helpful shape: a slope, a bar, a wheel. It has no engine, so you still do the pushing. It just makes the job feel easier. Six of them, all around the hous

Physics

Physics · L1 · Simple Machines

@openstem

Note~245 words · 1 min

Usually more than one push at a time Most things have several pushes or pulls acting on them at once. What happens next depends on whether those forces match each other. Tug of war A book sitting still Friction is the hidden one Roll a ball

Physics

Physics · L1 · Balanced & Unbalanced Forces

@openstem

Note~197 words · 1 min

Two kinds of energy you can watch Think of a swing pulled back and held. It isn't moving, but it isn't doing nothing either. It's ready to move, like it's holding its breath. The same swap, four ways The wind-up car is worth doing yourself.

Physics

Physics · L1 · Energy in Motion

@openstem

Note~227 words · 1 min

What fast means Speed is how quickly something covers ground. Fast means a lot of distance in a short time; slow means only a little in the same time. You compare speeds constantly without thinking. A car beats a bike, a bike beats walking.

Physics

Physics · L1 · Fast & Slow

@openstem

Note~249 words · 1 min

Stretchy or not Some things stretch easily: a rubber band, a spring, an elastic waistband. Pull them and they get longer, then snap back once you let go. A rock, a pencil or a spoon barely move however hard you push. What elastic actually m

Physics

Physics · L1 · Springs & Stretchy Things

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Note~238 words · 1 min

Heavy or light Pick up a feather, then pick up a brick. The brick pulls down on your hand much harder, and that pulling-down feeling is weight. Sometimes one in each hand is enough to tell. When two things feel close, you need a tool. The b

Physics

Physics · L1 · Weighing & Balancing

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Note~220 words · 1 min

White light is secretly every colour Sunlight looks plain white, but red, orange, yellow, green, blue and purple are all mixed together inside it. A prism is a shaped piece of glass that splits them apart. It bends each colour by a slightly

Physics

Physics · L1 · Rainbows & Mixing Colors

@openstem

Note~257 words · 1 min

Water has a stretchy skin The very top layer of water behaves differently from the water underneath. Those top molecules pull on each other sideways, making something like a thin stretchy skin across the surface. That's surface tension. It

Physics

Physics · L1 · Bubbles & Surface Tension

@openstem

Note~191 words · 1 min

A force that fights sliding Whenever two surfaces touch and try to slide past each other, friction pushes back against that sliding. It's why a rolling ball eventually stops instead of rolling forever, and why your feet grip the ground inst

Physics

Physics · L1 · Friction: Why Things Slow Down

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Note~219 words · 1 min

Some materials let heat rush through, some don't Heat is always moving from warmer things to cooler ones. But materials differ enormously in how fast they let it through. Why metal feels cold Trapping warmth Using both on purpose A cooking

Physics

Physics · L1 · Keeping Warm: Insulators & Conductors of Heat

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Note~214 words · 1 min

Two reasons light reaches your eyes When you see something, light travelled from it into your eyes. But there are two very different reasons that light was coming from it. The left column are light sources. Everything in the right column yo

Physics

Physics · L1 · Where Light Comes From

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Note~389 words · 2 min

Magnetic all by itself A permanent magnet needs no electricity, no wires, no switch. A fridge magnet is one. That's the difference from an electromagnet, which is only magnetic while current flows. Poles That's why a bar magnet grabs paperc

Physics

Physics · L2 · Permanent Magnets & Field Lines

@openstem

Note~259 words · 1 min

Friction opposes sliding Static vs kinetic Static friction is the reason a heavy box refuses to budge, then suddenly lurches. You beat the larger static value and the smaller kinetic one takes over. What changes how much friction you get Th

Physics

Physics · L2 · Friction

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Note~261 words · 1 min

A wave carries energy, not matter Drop a pebble in a pond. Ripples race outward, but a floating leaf just bobs and stays put. Transverse: the medium moves across the travel direction A stadium wave is the same shape: people stand and sit in

Physics

Physics · L2 · Wave Basics

@openstem

Note~232 words · 1 min

Two motions at once Throw a ball and two separate things happen to it the whole time it's airborne. It keeps moving forward in the direction you launched it, and gravity keeps pulling it straight down. Neither cancels the other. They add, a

Physics

Physics · L2 · Projectile Motion Basics

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Note~423 words · 2 min

Why you need it Exactly solvable quantum systems are a short list: harmonic oscillator, hydrogen, particle in a box. Everything else is one of those plus a small extra term, and perturbation theory is how you cash that in. Time-independent,

Physics

Physics · L5 · Perturbation Theory and Scattering

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Note~230 words · 1 min

What a pendulum is Anything that hangs from a fixed point and is free to swing. A playground swing is one: you're the hanging weight, and the chains attach to a fixed bar above. Why it goes back and forth That's why it keeps going instead o

Physics

Physics · L1 · Swings & Pendulums

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Note~196 words · 1 min

Rubbing moves tiny charges Everything is made of tiny particles carrying a little electric charge. Usually they're balanced, so nothing pulls or pushes. Rub two things together, like a balloon and your hair, and some of those charges rub of

Physics

Physics · L1 · Static Electricity: Balloons & Hair

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Note~235 words · 1 min

Wind is just air on the move Air surrounds you all the time even though you can't see it. When it moves, that's wind. Catching the push Some things are built with a big flat or angled surface specifically so wind has something to shove agai

Physics

Physics · L1 · Wind & Moving Air

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Note~270 words · 1 min

A special curved shape A magnifying glass isn't just any glass. It's thicker in the middle and thinner at the edges, like a small dome. That curve is what makes it a lens. Light travels straight until something bends it. A flat window barel

Physics

Physics · L1 · Magnifying Glasses & Simple Lenses

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Note~211 words · 1 min

A machine doesn't reduce the work It changes the force you need, or the direction you push, or both. The total work stays the same. They combine

Physics

Physics · L2 · Simple Machines

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