Chemistry is the science of matter — its composition, structure, properties, and the reactions by which it transforms. It spans from atomic structure and the periodic table to the complex molecular interactions in living cells. Read more
What is H2O commonly known as?
EasyWater H_2O is a polar inorganic compound that is the main constituent of Earth's hydrosphere and the fluids of all known living organisms. It consists of two hydrogen atoms covalently bonded to a single oxygen atom. Water is known as the "universal solvent" because it can dissolve more substances than any other liquid.
Water is one of the only substances on Earth that is less dense in its solid state than in its liquid state. This is why ice floats! If ice sank, the world's oceans and lakes would freeze from the bottom up, making it impossible for most aquatic life to survive the winter.
What is the value of 'g' (acceleration due to gravity) on Earth?
EasyThe standard value of 'g' (the acceleration due to gravity) on Earth's surface is approximately 9.81 m/s^2. This means that in the absence of air resistance, the velocity of a falling object increases by about 9.8 meters per second every second.
The value of 'g' is slightly higher at the poles and lower at the equator because the Earth is not a perfect sphere!
Which acid is present in lemon?
MediumCitric acid is the organic acid present in lemons, limes, oranges, and other citrus fruits. It gives these fruits their characteristic sour taste. Beyond flavor, citric acid is a natural preservative and is used in the food industry to add a sour or acidic taste to candies and soft drinks.
Lemons actually contain more sugar than strawberries! A lemon is about 7% sugar, while a strawberry is only about 5%. The only reason lemons taste so sour is because the extremely high concentration of citric acid (about 5% to 6%) completely overwhelms the sweetness of the sugar.
Which acid is found in vinegar?
MediumAcetic acid CH_3COOH is the acid found in vinegar. Household vinegar is typically a solution of about 5% to 8% acetic acid in water. It is produced by the fermentation of ethanol by acetic acid bacteria.
The word "vinegar" comes from the Old French "vin aigre," which literally means "sour wine"!
What is the force that opposes motion?
EasyFriction is the force that opposes the relative motion of two surfaces in contact. It acts in the opposite direction of the motion and is caused by microscopic irregularities on the surfaces. While friction can be a nuisance (like wearing down shoes), it is also essential for walking and for car brakes to work.
Without friction, you wouldn't be able to hold a glass of water-it would simply slip right through your fingers!
Which gas is released during volcanic eruptions mostly?
HardWater vapor H_2O is the most abundant gas released during volcanic eruptions, followed by carbon dioxide CO_2 and sulfur dioxide SO_2. While we often focus on the ash and lava, the gases released can have a major impact on the Earth's climate.
Large volcanic eruptions can release so much sulfur dioxide that it reflects sunlight away from Earth, causing a "volcanic winter" and cooling the planet for several years!
What is the atomic number of Carbon?
MediumThe atomic number of Carbon is 6, meaning it has six protons in its nucleus. Carbon is the fundamental building block of all known life on Earth because of its unique ability to form stable bonds with many elements, including itself.
Carbon can exist in very different forms, from the soft, black graphite in your pencil to the hard, clear diamond in jewelry!
What is the large landmass that existed millions of years ago?
MediumPangea (or Pangaea) was a massive supercontinent that existed about 335 to 175 million years ago. It contained almost all of the Earth's landmasses before it began to break apart due to plate tectonics, eventually forming the continents we recognize today.
If you look at a map of the world, you can see how the coastline of South America looks like it would fit perfectly into the coastline of Africa-they were once joined together in Pangea!
What is the chemical symbol for Silver?
EasyThe chemical symbol for Silver is Ag, which comes from the Latin word "argentum." Silver has been used for thousands of years for jewelry, coins, and high-quality mirrors.
Silver has natural antibacterial properties; in the days before refrigerators, people would sometimes drop a silver coin into a jug of milk to keep it from spoiling!
What is the chemical name for common table salt?
EasySodium Chloride NaCl is the chemical name for common table salt. It is an ionic compound composed of sodium Na^+ and chloride Cl^- ions. It is essential for life, helping to regulate fluid balance and nerve impulses in the body.
In ancient times, salt was so valuable that Roman soldiers were sometimes paid in it-this is where the word "salary" (from the Latin "sal" for salt) comes from!
What is the chemical symbol for Gold?
EasyThe chemical symbol for Gold is Au, which comes from the Latin word "aurum," meaning "shining dawn." Gold is a transition metal known for its distinct yellow color, malleability, and resistance to corrosion.
Gold is so malleable that a single ounce can be beaten into a translucent sheet covering nearly 100 square feet!
Which is a major source of water pollution?
MediumIndustrial waste, sewage, and agricultural runoff (containing pesticides and fertilizers) are major sources of water pollution. These pollutants can kill aquatic life and make water unsafe for human use.
When fertilizers run off into the water, they can cause "algal blooms" that use up all the oxygen in the water, creating "dead zones" where no fish can survive!
Which acid is present in an ant's sting?
MediumFormic acid CH_2O_2 is the acid present in an ant's sting. When an ant bites or stings, it injects this acid to cause irritation and defend itself. The name "formic" comes from the Latin word "formica," which means "ant."
Some birds actually rub ants on their feathers (a behavior called "anting") to use the formic acid as a natural pesticide against mites!
What is the process of cell division for reproduction called?
HardMeiosis is the specialized process of cell division that produces reproductive cells, such as sperm and eggs. Unlike regular cell division (mitosis), meiosis involves two rounds of division that result in four daughter cells, each with only half the number of chromosomes of the original parent cell.
Meiosis also involves "crossing over," where genetic material is swapped between chromosomes, ensuring that every sperm and egg cell is genetically unique!
What is the energy of motion called?
EasyKinetic energy is the energy an object possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. The formula is KE = frac12mv^2.
If you double the speed of a car, its kinetic energy actually quadruples, which is why high-speed crashes are so much more dangerous!
What is the atomic number of Oxygen?
MediumOxygen has the atomic number 8, meaning every oxygen atom has eight protons in its nucleus. It is a highly reactive non-metal and oxidizing agent that readily forms oxides with most elements. On Earth, it is vital for the respiration of most living organisms and for combustion.
While oxygen gas O_2 is clear, liquid oxygen is actually a beautiful pale blue color and is highly magnetic!
What is the pH of a strong acid?
MediumA strong acid has a very low pH, typically ranging from 0 to 2. The pH scale is logarithmic, meaning an acid with a pH of 1 is ten times more acidic than an acid with a pH of 2. Examples of strong acids include hydrochloric acid and sulfuric acid.
The acid in your stomach (hydrochloric acid) has a pH of about 1.5, which is strong enough to dissolve most metals!
What is the valency of Magnesium?
MediumThe valency of Magnesium is 2. This means that magnesium atoms typically lose two electrons to form a Mg^2+ ion in order to achieve a stable electron configuration. It is an alkaline earth metal with the atomic number 12.
Magnesium is highly flammable and burns with a brilliant, blinding white light; it was once used as the main component in camera flash powder!
What is the chemical formula for Chalk?
MediumCalcium Carbonate CaCO_3 is the chemical formula for chalk. It is a common substance found in rocks (like limestone and marble) and is the main component of pearls and the shells of marine organisms.
The iconic White Cliffs of Dover in England are made almost entirely of the microscopic skeletons of tiny sea creatures, which are pure calcium carbonate!
What is the term for a species that is at risk of extinction?
EasyAn endangered species is a species that is at a very high risk of becoming extinct in the near future. This can be due to habitat loss, poaching, or climate change. Examples include the Javan Rhino and the Mountain Gorilla.
When a species is successfully protected and its population grows, it can be "downlisted" to "threatened" or even removed from the list entirely, like the Bald Eagle!