CHEMISTRY GLOSSARY

filtration    →   filtriranje

Filtration is a procedure in which liquids are separated from the precipitate by passing a suspension through the filter. The precipitate remains on the filter and through it the filtrate passes. Gaseous heterogeneous mixtures can also be filtrated.

fire    →   vatra

Fire is the manifestation of rapid combustion, or combination of materials with oxygen. The flame is the visible portion of the fire.

flash point    →   temperatura zapaljenja

Flash point is the lowest temperature at which a liquid or volatile solid gives off vapour sufficient to form an ignitable mixture with the air near the surface of the liquid or within the test vessel (NFPA).

flotation    →   flotacija

Flotation is a procedure in which hydrophobic solid substances are separated from hydrophilic one using bubbles of air. If air is blow through a suspension, in which substances promoting easier creation of foam are added, bubbles of air are created which stick to the hydrophobic matter and carry it out to the surface.

glass    →   staklo

Glass is a brittle transparent solid with the molecular structure of a liquid. It is made by fusing together sand (SiO₂), soda (Na₂CO₃), and lime (CaCO₃) with small quantities other compounds. It is used for window panes and mirrors, for articles of table and culinary use, for lenses, and various articles of ornament.

foam    →   pjena

Foams are dispersions of gases in liquids or solids. The gas globule may be of any size, from colloidal to macroscopic, as in soap bubbles. Bakers’ bread and sponge rubber are examples of solid foams. Typical liquid foams are those used in fire-fighting, shaving creams, etc. Foams made by mechanical incorporation of air are widely used in the food industry (e.g. whipped cream, egg white, ice cream, etc.). Foams can be stabilized by surfactants.

fuel cell    →   gorivi članak

Fuel cell is a device that converts chemical energy into electrical energy. It is different from a battery in that the energy conversion continues as long as fuel and oxidising agent are fed to the fuel cell; that is, in principle indefinitely. (A battery is manufactured with a limited amount of chemicals, and it is exhausted when all the chemicals have reacted.) It is a galvanic cell where spontaneous chemical reactions occur at the electrodes. The fuel is oxidised at the anode, and the oxidising agent (almost always oxygen or air) is reduced at the cathode. Presently, the most commonly used fuel is hydrogen. More conventional fuels (e.g., petrol or natural gas) must be converted (reformed) into hydrogen before they can be utilised in a fuel cell.

Some fuel cells employ an aqueous solution as electrolyte, that can be either acidic or basic (alkaline), or an ion-exchange membrane soaked in aqueous solution can act as the electrolyte. These fuel cells operate at relatively low temperatures (from room temperature to not much above the boiling point of water). Some fuel cells employ molten salts (especially carbonates) as electrolytes and have to operate at temperatures of several hundred degrees centigrade (Celsius). Others employ ionically conductive solids as electrolyte and must operate close to 1 000 °C.

fugacity    →   fugacitet

Fugacity (f) is a thermodynamic function used in place of partial pressure in reactions involving real gases and mixtures. For a component of a mixture, it is defined by

where μ is the chemical potential.

The fugacity of a gas is equal to the pressure if the gas is ideal. The fugacity of a liquid or solid is the fugacity of the vapour with which it is in equilibrium. The ratio of the fugacity to the fugacity in some standard state is the activity.

Heat of atomisation    →   toplina atomiziranja

Heat of atomisation or enthalpy of atomisation is the energy required to dissociate one mole of a given substance into atoms.

heat of combustion    →   toplina izgaranja

Heat of combustion or enthalpy of combustion is the heat evolved when a definite quantity of a substance is completely oxidised (burned).