heavy water

  1. water in which hydrogen atoms have been replaced by deuterium, used chiefly as a coolant in nuclear reactors.

Origin of heavy water

First recorded in 1930–35

Words Nearby heavy water

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use heavy water in a sentence

  • At his side lay the torso of the young reporter, his head mashed by the heavy water-cooler.

    The Promise | James B. Hendryx
  • There is the artistic excitement of choosing the hook, gaudy for a heavy water, neat and modest for a clearer stream.

    Lost Leaders | Andrew Lang
  • The trout were all onannaniche and as game a fish for its size as I ever want to catch; in the heavy water they gave grand sport.

  • Anthea lifted down the heavy water-jug—it had a pattern of storks and long grasses on it, which Anthea never forgot.

British Dictionary definitions for heavy water

heavy water

  1. water that has been electrolytically decomposed to enrich it in the deuterium isotope in the form HDO or D 2 O

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for heavy water

heavy water

  1. Water in which deuterium, a heavy isotope of hydrogen, takes the place of hydrogen. Heavy water has physical and chemical properties that are like those of ordinary water, but heavy water is 10 percent heavier and has higher freezing and boiling points. Also called deuterium oxide. Chemical formula: D2O. Semiheavy water is similar to heavy water, but only one of the two hydrogen atoms in each molecule is replaced with deuterium. Chemical formula: DHO.

a closer look

The nucleus of most hydrogen atoms consists of a single proton, but in one isotope of hydrogen, called deuterium or heavy hydrogen, the nucleus also contains a neutron and thus weighs nearly twice as much as standard hydrogen. The substance called heavy water is chemically identical to ordinary water (H2O), except that the hydrogen atoms in the molecule are the deuterium isotopes (D2O). Heavy water makes up a small percentage (0.02%) of water naturally occurring on Earth. It is an excellent moderator for nuclear reactions, slowing down the fast neutrons produced in a nuclear fission reaction, increasing the likelihood that the neutrons will successfully collide with heavy nuclei to cause further fission. Although heavy water is chemically nearly identical with ordinary water, it is about ten percent heavier and interferes with cell mitosis if consumed in place of normal water. Ice cubes made of heavy water are denser than ordinary liquid water and will sink to the bottom of a glass of cola.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for heavy water

heavy water

Water with a higher average molecular weight than ordinary water. In a molecule of heavy water, the hydrogen atoms are isotopes in which the nuclei each contain a proton and a neutron, and hence are twice as heavy as a normal hydrogen atom.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.