Purificação por dissolução ou recristalização

A solubilidade de diversos sais num determinado líquido varia consoante a natureza do sal e do líquido. Por exemplo, a solubilidade do carbonato de sódio (Na2CO3) em água a baixa temperatura (cerca de 48,5 g/100 g de água a 100ºC) é bastante superior à solubilidade do carbonato de cálcio CaCO3, (cerca de 0,002g/100g a 100ºC). Diferentes sais também apresentam diferenças na variação da solubilidade com a temperatura. Por exemplo, a solubilidade do bicarbonato de sódio (NaHCO3) em água aumenta de 6,9 g/100g a a 0ºC para 16,4 g/100g a 60ºC, enquanto que a solubilidade do cloreto de sódio (NaCl) apenas aumenta de 35,7 g/100g a 0ºC para 39,8 g/100g a 100ºC. A solubilidade de determinado sal também varia consoante a natureza do solvente. Por exemplo, a solubilidade em álcool ou num solvente orgânico (p.e. acetona) pode ser bastante diferente da solubilidade em água. Por exemplo, a solubilidade do sulfato de cobre em água é muito mais elevada do que em etanol. Finalmente, o próprio valor do pH pode ser determinante da solubilidade. Por exemplo, o carbonato de cálcio em solúvel em meio ácido e é quase insolúvel em meio neutro ou alcalino. Os tipos de efeitos acima descritos podem ser usados em processos de separação ou purificação baseados em diferenças de solubilidade, variações de solubilidade com a temperatura, evaporação do solvente ou alteração do pH. Métodos semelhantes podem   também ser usados na obtenção controlada de pós de diversos materiais.


How does fluorescence work?

A description of what fluorescence is and its connection to variety of topics and disciplines of everyday life and science.



The New Frontiers of Engineering Award is an initiative promoted by the Portuguese Association of Engineers (Central Region) which aims to stimulate the interest of students in elementary and secondary education about STEM themes and in the engineering profession. Antimatter, was a work developed by students of the 12th year of Colégio da Imaculada Conceição, school and candidate for the prize in 2017. Consisting of the development of a device for collecting waste in polluted waters using renewable energy.


Bottleflip Challenge

When the bottle moves in the air, the liquid inside it begins to walk up the sides. This action rises up the moment of water inertia and reduces its rotation speed. This phenomenon is similar to what happens to a diver when he jumps from the top of a board to the swimming-pool.


Saccharose and oxygen transformation due to heat

Heat is one of the factors that can cause chemical transformations. One of the transformations envolves sugar, chemically known as saccharose, and air oxygen.


Relationship between mass and weight

The activity allows to determinate the relationship between the weight and the mass of a bodie, on Earth.


Simulation of weather conditions essential along the salt production process: Solar radiation effect on the evaporation rate

Having as background the Aveiro saltpans and all the procedure for obtaining salt from them (evaporation of water), an experience was planned in order to study the effect of solar radiation on the evaporation rate. A saltpan was simulated in the lab, prepared in a dark room (without natural sunlight), and, with a floodlight, we simulated the sun. We varied the angle of incidence of the radiation in the saltpan and then we measured the temperature as well as the range of mass of the saltpan during a certain hiatus of incidence of the floodlight. In order to study the water evaporation rate with and without wind, a fan was used.  


Transient - 4K, UHD, 1000FPS

Adjective. not lasting, enduring, or permanent; lasting only a short time; existing briefly. Philosophy. person or thing that is transient, especially a temporary guest, boarder, laborer, or the like. Electricity. a sudden pulse of voltage or current


pinners! - how do fidget spinners work? - Quick Physics Video

Fidget spinners work because there is a bearing in the centre. This is a good example of conservation of angular momentum, essentially the thing will keep spinning until there is an external moment, this is provided by the friction between the two rings. Ball bearings in between the two rings mean that as small as possible surface is touching between the two rotating rings, meaning friction is as low as possible. Skateboards, rollerblades, bikes and cars are all designed to waste as little as possible energy as heat and sound during friction between the axle and the wheel.


Synthesis of Fluorescent Quantum Dots

The visible absorption and photoluminescence of CdSe nanoparticles depend on the size of the particle. A sudden injection of room temperature selenium solution into hot cadmium solution produces quickly-growing seed crystals. Samples are withdrawn from the hot solution and quenched at room temperature to produce a series of increasing particle sizes and observable change in color.


Polimerização de uma resina de ureia-formaldeído

Os polímeros são constituídos por macromoléculas cuja massa molecular média depende do grau de polimerização. As macromoléculas de muitos polímeros são lineares, como sucede no polietileno ou policloreto de vinilo (PVC). Nestes casos, apenas existem ligações fracas (de van der Waals) entre as macromoléculas. Noutros polímeros formam-se cadeias reticuladas, como sucede na borracha vulcanizada. As propriedades dos polímeros dependem simultaneamente da massa molecular e da existência dessas ligações laterais. As macromoléculas são produzidas por reacções de polimerização, a partir de moléculas simples (monómeros). Nos polímeros lineares cada molécula de monómero reage passo a passo com uma das extremidades de uma macromolécula de modo a aumentar gradualmente a sua massa molecular


Is Glass really a solid?

A short presentation on the physical state of glass and how it is defined in terms of molecular structure, distances and order of molecules and formulation.


Environmental (Bio)monitoring

The New Frontiers of Engineering Award is an initiative promoted by the Portuguese Association of Engineers (Central Region) which aims to stimulate the interest of students in elementary and secondary education about STEM themes and in the engineering profession. Environmental (Bio)monitoring, was a work developed by students of the 7th year of Colégio da Imaculada Conceição, school and candidate for the prize in 2017. Consisting of the measurement, using microwave and radiofrequency, of the dielectric properties of leaves of the inula spiraeifolia plant in order to investigate its applicability to monitor environmental pollution. Comparing to contaminated water with different concentrations of heavy metals.


M&Ms in the water: Science with creativity

Chocolate M&Ms are covered by a layer of sugar and food colouring. When put into the water, the sugar gradually melts taking with it a certain amount of colouring which, in its turn, is also soluble in water. The sugar flows in the water from areas with a high concentration of sugar to areas with a lower concentration. At some point, the colours do not not mix anymore! A possible explanation is that in the border area between then, the sugar concentration is almost the same, diminishing the tendency of both the sugar and colouring flux.


Is the image of an object equal in any kind of mirror?

Characterisation of images obtained from flat and curved mirrors.


Magnesium combustion reaction

Verify and interpret the occurrence of the magnesium combustion reaction. Verify if the magnesium combustion reaction is an exoenergetic reaction which releases energy in the form of heat or light.


Water electrolysis

The decomposition of a substance by the action of electricity is called electrolysis. An example of one of these transformations is the decomposition of water by the action of electricity. This activity should be carried out under the supervision of your teacher.


4 Science Experiments at Home * Amazing Physics Tricks

It's amazing, informative and interesting Physics Science Experiments that you can do at home to repeat. Treat your household and friends of the wonderful tricks, and your knowledge of physics. Physical experiments and Science Tricks is cool and amazing!


Hydrocarbon Traps

A short video describing why and how hydrocarbons (crude oil, natural gas) may or may not be found in hydrocarbon traps in lower geological strata


Cabbage Indicator Experiment

Understanding how an acid-base indicator works in real life situations and how to make one at home. 

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