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Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 7_ P


potassium compounds
Compositions of the potassium

Potassium compounds. These compounds tend to be colorless, crystalline, and highly soluble in water. Potassium salts play an important role in the body:

Potassium iodide KI

The solution is useful as a solvent to dissolve iodine and form Kla3 (aqueous), which is used to test starch.

Potassium nitrate KNO3

Saltpetre rock salt. It is used in food preservation and explosives.

Potassium (VII) manganate KMnO4

A bright purple crystalline compound, it is a good oxidizing agent.


ppt
Abbreviation precipitate


precipitate (ppt)
Precipité m


Failed. The insoluble substance formed when two solutions are mixed in a double decomposition reaction is called a precipitate. like :

Pb(NO3)2 + 2NaCl → PbCl2 + 2NaNO3
(aqueous) (solid) (aqueous) (aqueous)

BaCl2 + Ma2SO4 → BaSO4 + 2NaCl
(aqueous) (solid) (aqueous) (aqueous)

In these two examples, lead(III) chloride and barium sulphate are precipitates.


pressure
pression f

Gauge pressure on the surface of a body. The SI unit for pressure is the pascal, and other units used are atmosphere and mm Hg.

The pressure exerted by the gas on its container results from the collision of molecules with the walls of the container. The gas pressure depends on its volume and temperature. See Boyle's gas law and laws and Charles' law.


proof
preuve f

proof. A measure of the percentage of ethanol present in a solution in water.


propane
propane m


Propane. Alkane is obtained from petroleum oil. It is mainly used as fuel:

C3H8 +502→3CO2 + 4H2O
(gas) (gas) (gas) (gas)

Although propane is a gas at normal room temperature, it is easy to liquefy and is sold packaged in gas bottles, as calor gas or camping gas, where it is mixed with butane.

C3H8


properties
features fpl

Properties Properties of matter are the distinctive ways in which it behaves (responds) in order to be what it is.
Which makes it different from other materials.

Properties are usually classified into physical properties and chemical properties. Chemical properties are concerned with the interactions of matter.

Physical properties include:

the color
Density
Physical condition
boiling point
Melting point
Crystal form
Solubility
Cruelty

Chemical properties include:

Whether the material is a metal or not a metal.
Whether it produces acidic or basic oxides.
If it has more than one equivalence.
Whether it reacts with acids.
Whether it is an oxidizing or reducing agent.


proteins
proteins mpl

Proteins. Large organic compounds composed of chains of amino acids. Amino acids are connected by peptide bonds. Proteins are widespread in the bodies of animals. They are found in skin, hair, nails, wool, cartilage, and muscles.

Proteins are a vital part of our diet. Good sources of protein are: meat, fish, eggs, milk, cheese, types of beans, and bread. Enzymes that play an important role in living organisms are nothing but protein molecules. Animals obtain the food they need to make proteins in their bodies by eating other animals or plants. Plants make proteins from nitrogen-containing compounds found in the soil. See fertilizers.


proton
proton m

Proton is a positively charged subatomic particle located in the nucleus of an atom. The number of protons in an atom is equal to the atomic number. Isotopes of any element always contain the same number of protons.


PTFE
pure pure

See poly(tetrafluoroethene).

pure. A substance is pure if it contains one element or compound, such as sodium chloride crystals that can be obtained in a pure state, but table salt is impure because it is mixed with other substances.

PVC (polyvinylchloride) polyvinylchloride m

See poly(chloroethene).


pyrolysis
pyrolyse f

Thermal decomposition. Decomposition of matter due to heat:
CaCO3 (solid) → Cao (solid) + CO2 (gas)