أكاديميا - كولنز - معاجم الجيب العلمية - الكيمياء - انكليزي - فرنسي - عربي الحرف ١_ l

Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 1_ L


to. 1 - Liquid, such as (l) H2O, (l) Hg, (l) H2SO4.

2 - Liter, a unit of volume equal to 1 dm3 or 1000 ml.

L

The symbol for the Avogadro constant is the number of particles in one mole of a substance. Its value is 2310 x 6 particles per mole.


latent heat
Change the latency

Latent heat. The amount of heat energy that is released or absorbed in a change of state at a given temperature (such as the boiling point or melting point) and the latent heat of fusion is the energy needed to convert one mole of a solid to a solid.
A liquid at its melting point.

Similarly, latent heat of vaporization is the energy needed to convert one mole of liquid into gas at its boiling point. The following symbols can be used:

ΔΗb
Where b = boiling (evaporation)

ΔΗm

Where m = melting

Examples:

Water Δ Ηm
= 6 kJ/mol
And ΔΗb
= 41 kJ/mol

Magnesium Δ Ηm
= 9 kJ/mol
And ΔΗb
= 129 kJ/mol


lattice
réseau m

network. An orderly arrangement of molecules, atoms, or ions within a crystalline solid. The networks contain large numbers of particles arranged in a very special way. In the following drawings are small sections of three networks, which are (a) aluminum
(b) Sodium
(c) Magnesium.

law of constant composition
Loi f de composition constante

The law of constant composition. A chemical compound always contains the same elements combined in the same proportion of mass.

Examples:
Water always contains hydrogen and oxygen in the ratio:
2/16 mass=1/8 mass=H/O

Carbon dioxide always contains carbon and oxygen in proportion
CO=12/32=3/8 mass


Law of multiple proportions loi / des proportions multiples

Law of multiple proportions. If two elements form more than one compound, there is a simple relationship between the masses of one of the two elements and a constant mass of the other element.

Example: nitrogen oxides.

Formula - ratio - simple ratio

Formula
N₂O
NO
NO2
N2O5

The ratio
(block) N:O
28:16
14:16
14:32
28:80

Simple ratio
14:8
14:16
14:32
14:40

There is a slight and constant increase in the oxygen to...
Nitrogen.


lead
plomb m

Lead is a dense metallic element in Group Iv of the periodic table. It is a soft, malleable, gray-colored element extracted from galena (PbS). Lead and its alloys have wide-ranging uses, such as accumulators
Lead-acid, soldering alloys and protection against
Humidity in house surfaces, radioactive isotopes, and X-rays.

Due to its chemical inertness, it can be used to store sulfuric acid.

lead compounds
Composés mpl du plomb

Lead Compounds Lead forms Pb(II) and Pb(17) compounds. And most lead compounds
Cumulative poisons.

Lead (II) nitrate Pb(NO3)2

The only common and soluble lead compound.

Lead(II) oxide PbO

Yellow oxide, or litharge, which is used in making glass and enamel.

Lead (IV) oxide PbO2

This oxide is formed in the lead-acid accumulator.

Tetraethyl lead Pb(C2H5)4

The anti-knock agent added to gasoline makes car engines run more smoothly. It is also a source of air pollution resulting from car exhausts.