CHEMISTRY GLOSSARY

specific quantity    →   specifična veličina

Specific quantity is often convenient to express an extensive quantity (e.g., volume, enthalpy, heat capacity, etc.) as the actual value divided by mass. The resulting quantity is called specific volume, specific enthalpy, etc.

molar quantity    →   molarna veličina

Molar quantity is often convenient to express an extensive quantity (e.g., volume, enthalpy, heat capacity, etc.) as the actual value divided by the amount of substance (number of moles). The resulting quantity is called molar volume, molar enthalpy, etc.

size of the nucleus    →   veličina jezgre

Size of the nucleus was measured by Lord Rutherford using the scattering patterns of alpha particles passing through a gold foil. It is 10^-15 m.

specific weight    →   specifična težina

Specific weight (γ) is defined as the ratio between the weight of a mass element, Δm, and the volume, ΔV, occupied by that element. As density (average) is defined as the ratio of a mass element and its volume, specific weight is equal to:

where g is gravitational acceleration.

specific heat    →   specifični toplinski kapacitet

Specific heat is the quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius.

sand filtration    →   pješčana filtracija

Sand filtration is a frequently used and very robust method of removing suspended solids from water. The filtration medium consists of a multiple layer of sand with a variety in size and specific gravity. Sand filters can be supplied in different sizes and materials, both hand operated and fully automatically.

relative density    →   relativna gustoća

Relative density (d) is the ratio of the density of a substance to the density of some reference substance. For liquids or solids it is the ratio of the density (usually at 20 °C) to the density of water at 4 °C. Since one must specify the temperature of both the sample and the water to have a precisely defined quantity, the use of this term is now discouraged. This quantity was formerly called specific gravity.

toxin    →   toksin

Toxins are effective and specific poisons produced by living organisms. They usually consist of an amino acid chain which can vary in molecular weight between a couple of hundred (peptides) and one hundred thousand (proteins). They may also be low-molecular organic compounds. Toxins are produced by numerous organisms, e.g., bacteria, fungi, algae and plants. Many of them are extremely poisonous, with a toxicity that is several orders of magnitude greater than the nerve agents. Botulinum toxin, produced by the bacteria Clostridium botulinum, is the most poisonous substance known.

acceleration    →   akceleracija

If a point-like object undergoes a change in velocity Δv=v_f-v_i in time Δt=t_f-t_i (indexes i and f stand for initial and final instant as well as for initial and final velocity) its average acceleration, a is defined as

The instantaneous acceleration, a, is obtained from the average acceleration by shrinking the time interval Δt towards zero. The average acceleration approaches a limiting value, which is the acceleration of a given instant:

Acceleration is a vector quantity. SI unit for acceleration is m s^-2.

activity    →   aktivitet

Activity (a) is a thermodynamic function used in place of concentration in equilibrium constants for reactions involving nonideal gases and solutions. For the species i activity is defined as

where a_i is the activity of the species i, c_i is its molar concentration, and f_i is a dimensionless quantity called the activity coefficient.