Photosynthesis, Food Webs, Stimuli, and Separation Methods
Photosynthesis
La fotosíntesi és un procés químic que converteix el diòxid de carboni en compostos orgànics, especialment utilitzant l’energia de la llum solar.[1] La fotosíntesi es produeix en les plantes.
Food Webs
Stimuli
Phase Changes
- Solid-Liquid: Fusion
- Liquid-Solid: Solidification
- Liquid-Gas: Vaporization
- Gas-Liquid: Condensation
- Solid-Gas: Sublimation
- Gas-Solid: Inverse Sublimation
Separation Methods
Sieving
Sieving is used to separate substances that are of different sizes. In this method, a sieve is used. The smaller components of the mixture can pass through the pores of the sieve, whereas bigger components of the mixture are retained by the sieve.
Filtration
Filtration is good for separating an insoluble solid from a liquid. (An insoluble substance is one that does not dissolve). Sand, for example, can be separated from a mixture of sand and water using filtration because sand does not dissolve in water.
Sedimentation
Sedimentation is a form of separating substances. This process involves letting an insoluble substance (a substance that will not dissolve in a solvent) settle at the bottom of a solvent. An example of this is if you mix chalk and water, the chalk will settle at the bottom of the glass after being mixed in because it does not dissolve in water.
Centrifuging
Centrifuging is a way of speeding up the process of sedimentation. A centrifuge, found in a laboratory, consists of many test tubes spinning at high speeds which inevitably forces the insoluble substance to the bottom quicker. A washing machine is a good example of this process. It spins quickly and water flies out through the holes in the sides, and the clothes stay in the washing machine.
Decanting
Decanting is somewhat the easiest of the two. It involves letting the mixture settle for a while. The heavier, insoluble substances will settle at the bottom of the liquid. A clear liquid will be left at the top. Once it is taken out, you have decanted the liquid. The impure substances are left behind.
Flotation
Flotation is a process of separating mixtures which involves separating substances by whether they sink or float. An example of this is oil and water; if they are stirred, the oil will rise on top of the water. Another example of this is if sawdust and sand are stirred in water, the sawdust floats and the sand sinks, separating the two substances.
Magnetic Separation
Magnetic separation is a form of separating mixtures which involves using a magnet to attract another magnetic object away from the substance it is in. Some examples of separating magnetic substances from non-magnetic substances are: separating iron nails from glass chippings and separating iron paper clips from brass ones.
Leaching
Leaching is the process of extracting minerals from a solid by dissolving them in a liquid, either in nature or through an industrial process. In the chemical processing industry, leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from beets using hot water.
Vaporization
Vaporization is used to separate components of soluble solid/liquid mixtures and volatile/involatile liquid mixtures. The principle governing this method is the fact that molecules of liquid substances when they gain heat, become gaseous and are lost from the surface. Notice that the liquid, having vaporized, is not collected but lost to the atmosphere. The other component (which is required) is then collected.
Distillation
Distillation is a process of separating the component substances from a liquid mixture by selective evaporation and condensation. Distillation may result in essentially complete separation (nearly pure components), or it may be a partial separation that increases the concentration of selected components of the mixture. In either case, the process exploits differences in the volatility of the mixture’s components.