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Pure water is an example of a chemical substance, with a constant composition of two hydrogen atoms bonded to a single oxygen atom (i.e. H 2 O). The atomic ratio of hydrogen to oxygen is always 2:1 in every molecule of water. Pure water will tend to boil near 100 °C
In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons. Nuclear scientists, however, define a pure element as one that consists of only one isotope. [18] For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each.
Steam and liquid water are two different forms of the same pure chemical substance, water. A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [13] [14] Chemical substances may take the form of a single element or chemical compounds.
A typical phase diagram.The solid green line applies to most substances; the dashed green line gives the anomalous behavior of water. In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. [1]
Pure water (H 2 O) is an example of a compound. The ball-and-stick model of the molecule shows the spatial association of two parts hydrogen (white) and one part oxygen (red) A chemical compound is a chemical substance composed of many identical molecules (or molecular entities ) containing atoms from more than one chemical element held ...
Pellets of soda lye (sodium hydroxide) Pellets of potash lye (potassium hydroxide)Lye is a hydroxide, either sodium hydroxide or potassium hydroxide.The word lye most accurately refers to sodium hydroxide (NaOH), [citation needed] but historically has been conflated to include other alkali materials, most notably potassium hydroxide (KOH).
The figure shows the schematic P-T diagram of a pure substance (as opposed to mixtures, which have additional state variables and richer phase diagrams, discussed below). The commonly known phases solid , liquid and vapor are separated by phase boundaries, i.e. pressure–temperature combinations where two phases can coexist.
Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. [25] Since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth (as in iron rusting), even small amounts of mercury can seriously corrode aluminium. For this reason, mercury ...