Have you ever wondered why plastic melts in a bonfire, but a cast iron pan doesn’t? A bonfire can reach temperatures as hot as 2,012 °F (1,100 °C). Most PET plastic melts at a measly 491 °F (255 °C), so it doesn’t stand a chance! Cast iron prevails with an average melting point of 2,100 °F (1,150 °C), depending on the iron-carbon alloy proportions.
The melting point of a substance is the temperature at which it changes from a solid to a liquid state. The reverse process of a liquid transforming into a solid is called the freezing (or crystallization) point, which is the same temperature as the melting point. In addition to temperature, pressure plays a crucial role in state changes. For most gas elements like nitrogen and helium, it requires more pressure than normal atmospheric pressure to condense them into a liquid. With that in mind, let’s explore this infographic by Alan’s Factory Outlet on the melting points of 80 elements, substances, and metal alloys.
You may have also wondered if any substance known would survive on the surface of the sun, which blazes ferociously at a temperature of 9,941 °F (5,505 °C). Sadly, not even the alloy tantalum carbide which has the highest melting point (6,960 °F or 3,850 °C) on this infographic would survive.
What about the other end of the spectrum? The coldest known object in the universe is the Boomerang Nebula at -458 °F (-272 °C). The element hydrogen’s melting (or freezing) point comes quite close at -434.4 °F (-259.1 °C). It has the lowest molecular weight of any known substance and burns with extreme intensity (5,500 °F), making it ideal to use as rocket fuel for spacecraft. It is considered cryogenic (requiring extremely low temperatures to liquefy and keep liquid), and therefore it requires immense care to create and store. In space, it needs to be shielded from the radiant heat of the sun in order to prevent colossal explosions. All of these factors demonstrate the immense amount of technical expertise possessed by NASA!