Chemistry facts

Hydrogen is the first element on the periodic table. It has an atomic number of 1. It is highly flammable and is the most common element found in our universe. More hydrogen facts. Liquid nitrogen boils at 77 kelvin (−196 °C, −321 °F). More nitrogen facts. Around 1% of the sun’s mass is oxygen. More oxygen facts. Helium is lighter than the air around us so it floats, that's why it is perfect for the balloons you get at parties. More helium facts. Carbon comes in a number of different forms (allotropes), these include diamond, graphite and impure forms such as coal. More carbon facts, diamond facts, and coal facts. Although it is still debated, it is largely recognized that the word 'chemistry' comes from an Egyptian word meaning 'earth'. The use of various forms of chemistry is believed to go back as long ago as the Ancient Egyptians. By 1000 BC civilizations were using more complex forms of chemistry such as using plants for medicine, extracting metal from ores, fermenting wine and making cosmetics. Things invisible to the human eye can often be seen under UV light, which comes in handy for both scientists and detectives. Humans breathe out carbon dioxide (CO2). Using energy from sunlight, plantsconvert carbon dioxide into food during a process called photosynthesis. Chemical reactions occur all the time, including through everyday activities such as cooking. Try adding an acid such as vinegar to a base such as baking soda and see what happens! Water expands as it drops in temperature, by the time it is frozen it takes up about 9% more space. Often formed under intense pressure over time, a crystal is made up of molecules or atoms that are repeated in a three dimensional repeating pattern. Quartz is a well known example of a crystal. Athletes at the Olympic Games have to be careful how much coffee they drink. The caffeine in coffee is a banned substance because it can enhance performance. One or two cups are fine but they can go over the limit with more than five. (update - as of 2004 caffeine has been taken back off the WADA banned list but its use will be closely monitored to prevent future abuse by athletes.)

What's the Difference?

Although there can sometimes be a blurry line between categories the following definitions should help you understand the difference between comets and asteroids, why Halley’s Comet is not a meteorite and more. Comet A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail. Asteroid Asteroids are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do. Meteoroid A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter (larger objects are usually referred to as asteroids). Meteor A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor. Meteorite A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.

Gravity

• Objects with mass are attracted to each other, this is known as gravity.

• Gravity keeps Earth and the other planets in our solar system in orbit around the Sun. It also keeps the Moon in orbit around Earth.

• Tides are caused by the rotation of the Earth and the gravitational effects of the Moon and Sun.

• Because Mars has a lower gravity than Earth, a person weighing 100kg (220 pounds) on Earth would only weigh 38kg (84 pounds) on Mars.

• It is thought that Isaac Newton’s theories on gravity were inspired by seeing an apple fall from a tree.

• While Newton’s older law of universal gravitation is accurate in most scenarios, modern physics uses Albert Einstein’s general theory of relativity to describe gravity.

• Acceleration of objects to due to the gravity on Earth is around 9.8 m/s2. If you ignore air resistance (drag) then the speed of an object falling to Earth increases by around 9.8 metres per second every second.

• The force of gravity 100 kilometres (62 miles) above Earth is just 3% less than at the Earth’s surface.

• The human body can handle increased g-forces as seen in activities such as dragster races, airplane acrobatics and space training. The highest known acceleration voluntarily experienced by a human is 46.2 g by g-force pioneer John Stapp.

• While formula one racing drivers may feel around 5 g’s under heavy braking, they can experience over 100 g’s if a crash causes them to decelerate extremely quickly over a very short distance.

• Some roller coasters have been known to include g-forces of around 4 to 6 g.

• The higher something is, the greater its gravitational potential energy. Back in the Middle Ages, weapons called trebuchets were used to take advantage of this principle, using mechanical advantage and the gravitational potential energy of a counterweight to hurl rocks and other projectiles at or over walls. In modern times we use the gravitational potential of water to create hydroelectricity.