The key words for Grade 6 science and the Cargo Ship Rescue breakout — in plain language, with an example for each. Keep this open while you solve the locks.
💧 Matter & Density
matter
Anything that has mass and takes up space.Example: air, water, a steel crate — all matter.
mass
How much "stuff" is in an object. We measure it in grams or kilograms.Example: a loaded crate has more mass than an empty one.
volume
How much space an object takes up.Example: a big hollow hull has a large volume.
density
How tightly mass is packed into a space. Density = mass ÷ volume.Example: a steel bar is very dense; foam is not.
fluid
A liquid or gas that can flow, like water or air.Example: a ship floats in the fluid we call water.
float / sink
An object floats when its overall density is less than the fluid's, and sinks when it is more.Example: a hollow ship floats; a solid bar sinks.
mixture
Two or more materials mixed together but not chemically joined.Example: sand stirred into water.
chemical change
A change that makes a new substance. Clues include a gas, a color change, heat, or a solid forming.Example: iron rusting.
🧲 Forces & Motion
force
A push or a pull on an object.Example: a wave pushing a crate sideways.
gravity
The force that pulls objects down toward Earth.Example: gravity pulls the crate onto the deck.
friction
A force that resists sliding when two surfaces rub.Example: friction keeps the crate from sliding at a small nudge.
normal force
The upward push a surface gives to an object resting on it.Example: the deck pushes up on the crate.
net force
The total force left over after you add up all the forces on an object.Example: if pushes cancel out, the net force is zero.
balanced forces
Forces that add up to zero, so the object's motion does not change.Example: a crate sitting still on the deck.
unbalanced forces
Forces that do not add up to zero, so the object speeds up, slows down, or changes direction.Example: a wave's extra push makes the crate slide.
Newton's Third Law
For every force there is an equal and opposite force on the other object.Example: the propeller pushes water back; the water pushes the ship forward.
⚡ Energy
energy
The ability to make something move or change.Example: the crane uses energy to lift a crate.
potential energy
Stored energy, ready to be used. A lifted object has gravitational potential energy.Example: a crate held high by the crane.
kinetic energy
The energy of a moving object.Example: the crate speeding up as it lowers.
energy transfer
Energy moving from one object or form to another.Example: electrical energy becomes motion.
conservation of energy
Energy is never created or destroyed. It only changes form or moves.Example: the crane's energy is never "used up" — it changes form.