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Isotopes are variants of the same chemical element with an equal number of protons in the nucleus but a different number of neutrons, resulting in a different atomic mass. An element is determined by the unique number of protons it has, also known as its atomic number. For example, the atomic number of carbon is 6 because it always has Read more...

Atoms have no overall charge because they contain an equal number of protons and electrons. A proton has a positive charge of the same magnitude as the negative charge carried by an electron. The positive charge of the protons is cancelled by the negative charge of the same number of electrons, and hence an atom is electrically neutral overall. Read more...

The Spanish verbs ‘llevar’ and ‘tomar’ can both be translated as ‘to take’ in English but have different meanings and are only interchangeable in a limited number of use cases. Use ‘llevar’ in situations when one is taking, by way of carrying, something from one place to another or taking someone to somewhere or an event. For example: Llevo a Read more...

Bison and buffalo are different species of animal, although they both belong to the Bovinae subfamily of the Bovidae family of cloven-hoofed, ruminant mammals. Bison are large, shaggy-haired horned mammals native to North America and Europe, and while they are often colloquially referred to as ‘buffalo’, they are not true buffalos. Buffalo are large, horned mammals native to Africa and Read more...

A donkey is not a horse, although they belong to the same family of animals, equidae, however they are different species. Donkeys tend to be smaller than horses and have longer ears and a distinctive bray. A donkey has 62 chromosomes while a horse has 64. Donkeys and horses can breed, with a male donkey and female horse producing mules, Read more...

Oxytocin is a peptide hormone and neurotransmitter that plays an important role in regulating the process of carrying a fetus, childbirth and lactation. It is also associated with influencing emotional attachment with others and social behavior, including recognition, empathy, trust, sexual activity, and the forming of bonds and relationships. Oxytocin is produced by cells in the brain’s hypothalamus and released Read more...

The human body has three types of blood vessel: Arteries which carry blood away from the heart. Veins which carry blood back towards the heart. Capillaries which connect arteries and veins, and are the smallest blood vessels. The blood vessels form a closed loop network of tubular channels connected to the heart, whose function is to carry blood to and Read more...

On average, sunlight takes 8 minutes and 19 seconds to reach Earth, given an average distance of 150 million kilometers (or 93 million miles) from the Sun and a speed of light of 299,792 kilometers per second. This number is an average because the Earth’s orbit around the Sun follows an elliptical path, so the distance between the surface of Read more...

Fiat currency is legal tender issued by a government, which has no intrinsic value and is not backed by a commodity of value, such as gold or silver. Its value is essentially underpinned by the stability and creditworthiness of the issuing government. Most major currencies are now classed as fiat money, including the US dollar, pound sterling and the euro, Read more...

Run flat tires have additional structural rigidity built-in, either through stiffer sidewalls or an inner support ring, enabling the tire to bear vehicle weight even when not fully inflated, unlike a conventional tire. A standard tire relies almost entirely on internal air pressure to give it sufficient rigidity to support a vehicle’s weight. In the event of a puncture, it Read more...

The definition of an oil is any nonpolar substance that exists as a viscous liquid at ambient temperatures and has the characteristics of being both hydrophobic (meaning it does not mix with water) and lipophilic (and so mixes with other oils). Different chemical compounds that share these characteristics may be classed as oils, although they may have no other similarities Read more...

When an apple is sliced open, the flesh exposed to air turns brown due to a series of biochemical reactions called enzymatic browning. The flesh inside an apple is made up of tiny cells containing, among other things, naturally-occurring polyphenol molecules and an enzyme called polyphenol oxidase. When an apple is cut or bruised, some of the cells are broken Read more...

Sunscreen products such as sun tan lotion contain chemical components that reduce the amount of the sun’s ultraviolet (or UV) radiation that reaches the skin. The active ingredients in sunscreen work by blocking the UV rays from the skin by reflecting them away or chemically absorbing them and converting the light energy into heat energy. The physical ultraviolet-reflecting sunblock components Read more...

AM radio signals can often be received from extremely distant transmitters at night due to changes that occur in the earth’s ionosphere after dark. The ionosphere is an atmospheric layer of electrically-charged atoms, molecules and free electrons that mainly arise due the ionizing effect of the sun’s ultraviolet radiation. The ionosphere extends closer to the earth’s surface during daylight, and Read more...

It is possible to get a tan through an ordinary glass window but much more slowly than when exposed to sunlight directly in the open air. Sunlight reaching us on earth contains two types of ultraviolet (or UV) rays, called UVA and UVB. Glass filters sunlight passing through a window and removes most of the UVB rays, the type that Read more...

Caffeine is a nitrogen-containing organic compound that is classed as an alkaloid and known by the IUPAC name 1,3,7-trimethylpurine-2,6-dione. In common with many other alkaloids, it is a naturally occurring compound of plant origin that has strong biological effects on animal and human organisms. One of the most common sources of human caffeine consumption is coffee drinks, and its stimulant Read more...

A frog is an omnivore, eating both plants and animals, although more accurately described as a life-history omnivore as it feeds on different types of food through its life stages. Tadpoles, the aquatic larval stage of a frog, are herbivores, feeding only on plant material before becoming mostly carnivorous once they have developed into frogs. Read more...

Each nitrogen molecule is two nitrogen atoms bound together by a very strong triple covalent bond. Its strongly bonded symmetrical structure makes nitrogen very stable and unreactive, requiring a lot of energy to break the bond within the molecule, significantly more than is available at room temperature. The attractive forces between nitrogen molecules themselves are dispersion forces (or London forces). Read more...

A Brocken spectre is a visual effect in cloud or mist where a person sees their shadow with colored concentric rings centered around the head. It occurs at high elevations like mountain peaks when sun directly behind an observer casts their shadow on cloud or mist below. The colored rings, called a glory, arise from backscattering of sunlight that has Read more...

Orbitals, the regions around an atom’s nucleus likely to be occupied by electrons, are grouped into subshells identified by energy level (1, 2, 3, 4 and so on) and orbital shape (s, p, d, and f). The 3d subshell contains five orbitals, each able to hold up to 2 electrons, a total of 10 electrons if all filled. Transition metals Read more...