Normal Water (H20) has hydrogen atoms with one proton and Heavy Water (D20) has a neutron and a proton in it H2 atoms.
Since heavy water contains an isotope of hydrogen 2H or more commonly called Deuterium means that the hydrogen atom in heavy water will have an extra neutron in the nucleus.
Heavy water occurs naturally in all water in a proportion of about one part in twenty million. In order to get a certain amount of heavcy water you have to isolate the heavy molecules out of a large quantity of water. The Germans used fresh water because there would have been no point in having to desalinize before they could even begin isolating the heavy water from the regular water. Heavy water is heavy because one of the hydrogen atoms in the water molecule has a neutron in its nucleus along with the proton.
Type your answer here... The hydrogen atoms in heavy water have a neutron in the nucleus, doubling the mass.
Normal water is made of H2O. That is: two hydrogen atoms and one oxygen atom. Heavy water is made of 2H2O (also known as D2O). That is: one deuterium atom and one oxygen atom. Deuterium is a variation of hydrogen which has a neutron in its nucleus (normal hydrogen has no neutrons). Do not confuse heavy water with H2O2, which is simply hydrogen peroxide.
The most common coolant used in nuclear reactors is water. There are light water reactors (using "regular" water), and the heavy water kind of reactor.
Many pressurized water reactors use "regular" water (light water) as a primay coolant. That means that "only heavy water" is not a rule as regards reactor design. Reactor design specifies the coolant to be used.
The boiling point of heavy water is higher than "regular" water because the water is a bit more massive (owing to the extra neutrons stuck to protons in hydrogen nuclei) and more energy is needed to allow the heavy water to change state. Boiling means the molecules gain kinetic energy and "escape" the bonds that are holding the water molecules together in their liquid state. Those same bonds act on the heavy water molecules just like "light" water, but because those molecules are a bit more massive, heavy water molecules need more kinetic energy to "break loose" and "escape" the liquid. That means higher temperatures are required for higher concentrations of heavy water to bring it to a boil. A link is provided to the Wikipedia article on heavy water.
Heavy water (D2O) is water created using the Deuterium isotope of Hydrogen, and is about 11% more dense than normal water but is still physically and chemically very similar to regular H2O. Heavy water is commonly used as a nuclear reactor moderator (slow down the neutrons to sustain the fission reaction). see related link
So you take some water...a lot of it. Then you have heavy water.
Pure heavy water is practically not conductive.
No heavy water in the muffler.
A swimsuit is not very heavy it only get a little heavy when we come out of water as it retains water