Speed
Speed tells you how much distance you cover per unit of time. With v=
Topics
All topics
Pick a topic. Every topic starts from an observation, shows a picture to play with, explains why, lets you practise and gives you an experiment for home.
16 topics
Physics
Speed, forces and balance, energy transfers and the electric circuit.
Physics s/t you work out speed, distance or time, in km/h or in m/s. Physics Forces and balance
A force is a push or a pull, measured in newtons. When all the forces on an object cancel each other out, it is in balance and its motion does not change.
Physics Energy transfers
Energy is never lost: it changes from one form into another. Almost always, part of it ends up as heat that you can no longer use.
With Kaft PlusPhysics The electric circuit
A bulb only lights up in a closed circuit of battery, wires and lamp. Connected in series or in parallel, bulbs behave differently.
Chemistry
States of matter, density, separating mixtures, acids and bases.
With Kaft PlusChemistry Solid, liquid and gas
Every substance is made of tiny particles that never stop moving, and the warmer it gets, the faster they go. That is how ice turns into water and water into steam.
With Kaft PlusChemistry Density: float or sink
Density tells you how much mass is packed into each cubic centimetre of a substance. If an object is less dense than the liquid around it, it floats.
With Kaft PlusChemistry Separating mixtures
Most materials around you are mixtures. Because the substances in them differ in size, boiling point, magnetism or density, you can take them apart again.
With Kaft PlusChemistry Acidic, neutral and alkaline
The pH scale from 0 to 14 shows how acidic or alkaline a substance is. Below 7 is acidic, 7 is neutral, above 7 is alkaline.
Biology
The cell, photosynthesis, food chains and digestion.
With Kaft PlusBiology The cell
Everything that lives is made of cells. A plant cell and an animal cell look alike, but a plant cell also has a cell wall, chloroplasts and a large vacuole.
With Kaft PlusBiology Photosynthesis
Plants make their own food. In their chloroplasts they use light energy to turn water and carbon dioxide into glucose. Oxygen is given off along the way, the oxygen you breathe in.
With Kaft PlusBiology Food chains
Who eats whom? Plants make food, animals eat plants or other animals, and decomposers break everything down again. Together they form a food web in which energy is passed along.
With Kaft PlusBiology Digestion
A mouthful of food travels about eight metres through your body. Along the way it is ground up and broken down into small building blocks that reach every cell through your blood.
Earth and space
Day and night, the seasons, the phases of the Moon, the solar system and gravity.
With Kaft PlusEarth and space Day, night and the seasons
The Earth spins on its axis once every 24 hours: that gives us day and night. Over a year it travels around the Sun, and its tilted axis creates the seasons.
With Kaft PlusEarth and space Phases of the Moon
The Moon does not give off light of its own. It reflects sunlight. As it travels round the Earth in about 29.5 days, we keep seeing a different part of its lit half.
With Kaft PlusEarth and space The solar system
The Sun is a star with eight planets around it: four small rocky planets close by and four giants far away. The distances between them are unimaginably large.
With Kaft PlusEarth and space Gravity
Your mass in kilograms stays the same everywhere. Your weight, the force of gravity on you in newtons, depends on where you are: G=
m× g.