What Is the Food Chain?
A food chain shows how energy passes from one living thing to another as they eat and are eaten. This guide explains producers, consumers…
Priya Anand
426 reading now
Science
Research, discovery and the natural world — from the cosmos to the cell.
185 stories
What Is pH?
The pH scale measures how acidic or alkaline a liquid is, from 0 to 14. This guide explains what the numbers mean, why each step is a…
Priya Anand
415 reading now
What Is Density?
Density is how much mass is packed into a given volume of a substance. This guide explains the simple formula, why a kilogram of steel…
Priya Anand
460 reading now
What Is Friction?
Friction is the force that resists movement when two surfaces touch. This guide explains where it comes from, the difference between static…
Priya Anand
360 reading now
What Is the Speed of Sound?
The speed of sound is how fast a sound wave travels through a material. This guide explains why it is roughly 343 metres per second in air…
Priya Anand
358 reading now