It reacts with water to produce hydrogen and calcium hydroxide. It reacts with water very fast when it is powdered. When it is in a chunk, it starts reacting slowly because calcium hydroxide makes a coating that does not dissolve on the calcium. If a little acid is added to calcium hydroxide, it dissolves it, making the calcium react very fast. It burns when powdered to make a reddish flame. This makes calcium oxide. It also makes calcium nitride when heated. It can react with halogens to make calcium halides like calcium chloride with chlorine.
Calcium forms chemical compounds in the +2 oxidation state. Calcium compounds are colorless. Most calcium compounds are not toxic. They are needed in the human body, actually. They are unreactive as far as calcium ions go. Calcium oxide was used to make limelights, which have a flame heating calcium oxide and makes it glow very bright.
Calcium has 6 naturally occuring isotopes (Ca, Ca, Ca, Ca, Ca and Ca), of which Ca is very slightly radioactive with a half-life about 6.4×10 years. Traces of Ca, Ca and Ca are made by cosmic rays striking atoms, and are called cosmogenic nuclides. Ca is made by the neutron activation of Ca in the upper layers of the Earth's crust and has a half-life of 102,000 years. Since it decays to potassium-41, it is a critical indicator of solar system anomalies.
Calcium-40 is the most abundant isotope (96% of all natural calcium), since it comes from radiogenic K, which has a half-life of 1.25 billion years. However, along with calcium-46, it is theoretically unstable but with a half-life so long it has never been observed to decay.
Calcium is not found as a metal in the ground; it is too reactive. Calcium carbonate, also known as calcite, is the most common calcium mineral.
It is important to know how cells work. Many cells have "calcium channels" on their surface. These are openings where calcium ions can enter the cell. The cell is told to act and it opens the channels. Once in the cell calcium ions activates many proteins to do specific things. For example, when it goes into muscle cells, it makes them "contract" (shorten so the muscle pulls.) When it goes into nerve cells, it triggers electrical impulses that send a messages. When it goes into white blood cells it makes them fight germs.
Calcium ions are important to cells, but too many calcium ions can be bad. If a cell gets more calcium ion than it needs it can die. This is why the amount of calcium ion in cells is highly regulated. Conversely, not enough calcium ion is bad. Cells must have the right amount to function properly.
Sometimes cells are unhealthy and need to die in for the body to replace them with new, healthy cells. This keeps the whole organism healthy. Cells know when they should die and can trigger reactions to end their life cycles in many ways. When this happens it is called apoptosis, also known as a 'programmed cell death' ("planned" cell death.) One way cells accomplish "apoptosis" by taking in toxic levels of calcium ions.
Calcium is very important for the human body.
Bones contain most of the calcium ion in the human body. If we need more calcium for our blood, muscles, or other tissue, it comes from the bones. If we have extra calcium it goes into bones.
Calcium as an element is not found in the human body, just calcium ions in the form of chemical compounds.
Organisms need to keep calcium ion levels very well controlled. High calcium levels are bad, and low calcium levels are bad.
The body controls this by changing
The control of calcium in the body is called "calcium metabolism". Too little calcium can cause osteoporosis.
The body controls calcium levels with many hormones. Calcitonin, Parathyroid hormone (acronym PTH), and Vitamin D are the most important hormones in "calcium metabolism". (Vitamin D works as a hormone but it is called a vitamin.)
Calcium metal is made by electrolysis of melted calcium chloride. It has to be very hot to melt it. The calcium metal is liquid.
Calcium is used in the reduction of other metals. It can also be used to make alloys with other metals.
Calcium compounds are also important in chemistry. It is important for making things. It is a part of cement which is needed to make concrete (a hard substance that many buildings are made from.)
Calcium is part of calcium oxide. Calcium oxide is used to make paper, pottery, food, and to purify water (make it good to drink.) Calcium carbonate is used as a calcium supplement. Calcium permanganate can be used as a rocket propellant.
Calcium is toxic as an element. It reacts with water and makes a strong base, calcium hydroxide. Calcium compounds are not toxic unless the anion is toxic. Calcium permanganate is only toxic because of the permanganate, not the calcium. Like other alkaline earth metals calcium burns easily and brightly.
A Series of Unfortunate Events
A Series of Unfortunate Events is a series of 13 books written for children by the author Lemony Snicket. They tell the story of three unlucky orphans (Violet Baudelaire, Klaus Baudelaire, and Sunny Baudelaire) and their lives after the death of their parents. The main villain of the books is Count Olaf who wants to steal Baudelaires' inheritance (the money their parents left behind). Count Olaf uses many disguises to get their fortune.
In 2004, there was a movie version, "Lemony Snicket's A Series of Unfortunate Events," from Paramount Pictures and Nickelodeon movies, starring Jim Carrey as Count Olaf.
In 2012, a new series from Lemony Snicket named All the Wrong Questions was written. The series tells the story of Lemony Snicket, a member of a group named V.F.D which is an important part of the series, when he was a child.
In 2016, the series was broadcast through Netflix (children's section).
Membrane
A membrane is a thin soft layer of material. A membrane separates two things.
In biology a membrane can mean two things: a tissue membrane or the membranes of a cell. The membranes of cells are very small, while tissue membranes are larger.
A membrane can mean a thin layer of cells or tissue. This layer covers the body or an organ, or separates, or lines a body cavity. An example is the mucous membrane that is the "skin" that lines the inside of your nose and mouth. An epithelial membrane has two parts, one part is epithelial tissue and the other is connective tissue.
There are many different types of membranes in a cell. The cell membrane, also called the plasma membrane, covers one cell. Membranes also divide the cell into different spaces called organelles. Organelles are special areas of the cell that do different work. For example, the nucleus holds the DNA in a cell. The mitochondria make energy for the cell.
Membranes in cells are made of lipids (fats) and protein. The lipids keep the inside of the cell or the organelle separate from the outside. The proteins do many things. Plasma membranes give the cell messages from outside. They let some things (like glucose, calcium, and potassium) go into and out of the cell.
Voltaire
François-Marie Arouet (also known as Voltaire) was a French philosopher. He was born in 1694 and grew up in Poitou. He died in Paris in 1778.
Voltaire did not like France at the time because he thought that it was old fashioned. He also did not like the Church and thought that people should be allowed to believe what they want. However he did not like democracy either and thought that a country needed to be led by a wise and strong king. Voltaire had to live in exile in England for three years from 1726 to 1729 where these ideas were more common. He liked the philosophy of John Locke.