Pure water contains no impurities and freezes at 0°C. However, seawater – on average – contains 3.5 per cent of dissolved salts, which lowers the freezing point; this phenomenon is called freezing point depression. Freezing point depression is a colligative property of matter, which means it depends on the number of molecules present, not on the specific type of molecule or their mass (i.e. the dissolved substance doesn't have to be salt, but any soluble substance, it's the amount of dissolved molecules that is important). In terms ...

Things are always cooler when slowed down, just ask John Woo. In that vein, check out this cool but also very funny video of a rather unfortunate chap being hit full in the face with a water balloon. This type of slow motion effect is achieved when each film frame is captured at a rate much faster than it will be played back, so when replayed at normal speed, ...

These long white clouds you are referring to are called condensation trails or contrails. Jet fuel is made of carbon and hydrogen which burns in the presence of oxygen. In this reaction some of the carbon joins with the oxygen to make CO2 (carbon dioxide) and some of the hydrogen joins with the oxygen to make H2O (water). The water which comes out of the engine is invisible water vapour but as soon as it is exposed to the colder temperatures of the upper atmosphere, it condenses ...

For life to prosper water is a fundamental necessity, but if so, how did the the ancient Maya build such a massive empire without a river to draw water from? This, the first of five videos from the BBC documentary Secrets of the Mayan Underworld, demonstrates how through a series of underground, water-filled caves that run under the majority of the Yucatan, the Mayan Underworld – contrary to their belief that it was a realm of spirits – was actually the life-source of the entire area....