Facts about calcium, and the reaction of calcium with oxygen
Physical and chemical properties of calcium
In ancient times, people used calcium compounds for building, mainly calcium carbonate, which was found in rocks, or lime, which was made from baking it. They also used marble and gypsum. Right up until the end of the 18th century, scientists mistakenly believed that lime, which is calcium oxide, was an element, until Antoine Lavoisier proposed his theories about the substance.
In the early 19th century, the English scientist Humphrey Davy discovered calcium in pure form, using electrolysis. He obtained a calcium amalgam from slaked lime and mercury oxide. By removing the mercury, he got metallic calcium.
Calcium plays an important role in biology, and is a widespread microelement found in small quantities in the human body, in animals and also in plants. A deficiency of this element leads to various diseases.
As the metal displays high activity, in nature calcium is not encountered in free form. The majority of compounds are in rocks, for example silicates and aluminosilicates. It is also found in sediment rocks, for example in limestone and chalk, which are made of calcium carbonate, and also in seawater and underground water in the earth’s crust.
Application of calcium
This element is often used in the metallurgical industry, where calcium is used as a reducer to obtain several metals, for example stainless steel.
Other calcium compounds used in industry:
calcium oxide CaO or quicklime, which is used in building and repair works;
calcium hydrosulfate Ca(HSO₃)₂ consists of colorless crystals, and is a preservative, which is also used in the paper industry;
calcium sulfate dihydrate or gypsum CaSO₄·2H₂O is used as a bonding material in the paper and cellulose industry, and in medicine for holding fractures in place.
Physical properties of calcium
Ca is a soft metal, which can easily be cut with a knife;
Calcium has a shiny silvery-white color, which grows dull from the formation of an oxide film when stored incorrectly;
it has a high melting point – 842 degrees Celsius.
it has high electricity and heat conductivity;
it boils at a temperature of 1484 degrees Celsius.
Chemical properties of calcium
Ca is located in the second group of the fourth period in the periodic table. Calcium is an active alkaline earth metal.
Calcium should be stored in kerosene, because if the metal is left in the open air, it swiftly loses its metallic shine and becomes dull and grey from the impact of water vapor, oxygen and carbon dioxide.
Calcium reacts violently with water, but without ignition. The abundant release of hydrogen causes the piece of calcium to move around in the water. Calcium hydroxide also forms. If phenolphthalein is added to the liquid, it turns a bright crimson color, which proves that Ca(OH)₂ is a base.
Ca + 2H₂O → Ca(OH)₂↓ + H₂↑
The reaction of calcium with oxygen
The reaction of Ca and O₂ is very interesting, but this experiment must not be conducted at home, as it is very dangerous.
Let us examine the reaction of calcium and oxygen, and namely the combustion of this substance in air.
Warning! Don’t try to repeat this experiment without a professional supervision! Here you’ll find safe chemistry experiments to do at home.
As a source of oxygen, we will take potassium nitrate KNO₃. If calcium is stored in kerosene, before the experiment we must clean it with a spirit burner, holding it above the flame. We then place the calcium is KNO₃ powder, making sure it is well-covered. Then we place the calcium with potassium nitrate in the flame of the burner. The potassium nitrate breaks down into potassium nitrite and oxygen. The oxygen released burns the calcium, and the flame turns red.
KNO₃ → KNO₂ + O₂
2Ca + O₂ → 2CaO
We should note that calcium only reacts with certain elements when heated – they include phosphorus, sulfur, boron, nitrogen and others.