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examples of mixture separated through sublimation

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From Wikipedia


In chemistry, a mixture is a material system made up by two or more different substances which are (mixed) together but are not combined chemically. Mixture refers to the physical combination of two or more substances the identities of which are retained. The molecules of two or more different substances are mixed in the form of alloys, solutions, suspensions, and colloids.

Mixtures are the product of a mechanical blending or mixing of chemical substances like elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup. Nonetheless, despite there are no chemical changes to its constituents, the physical properties of a mixture, such as its melting point, may differ from those of the components. Some mixtures can be separated into their components by physical (mechanical or thermal) means. Azeotropes can be considered as a kind of mixture which usually pose considerable difficulties regarding the separation processes required to obtain their constituents (physical or chemical processes or, even a blend of them).

Mixtures can be either homogeneous or heterogeneous. A homogeneous mixture is a type of mixture in which the composition is uniform. A heterogeneous mixture is a type of mixture in which the composition can easily be identified, as there are two or more phases present. Air is a homogeneous mixture of the gaseous substances nitrogen, oxygen, and smaller amounts of other substances. Salt, sugar, and many other substances dissolve in water to form homogeneous mixtures. A homogeneous mixture in which there is both a solute and solvent present is also a solution.

The following table shows the main properties of the three families of mixtures.

The following table shows examples of the three types of mixtures.

Physics and Chemistry

A heterogeneous mixture is a mixture of two or more compounds. Examples are: mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a salad, trail mix, and concrete (not cement). Gy's sampling theory quantitatively defines the heterogeneity of a particle as:

h_i = \frac{(c_i - c_\text{batch})m_i}{c_\text{batch} m_\text{aver}} .

where h_i, c_i, c_\text{batch}, m_i, and m_\text{aver} are respectively: the heterogeneity of the ith particle of the population, the mass concentration of the property of interest in the ith particle of the population, the mass concentration of the property of interest in the population, the mass of the ith particle in the population, and the average mass of a particle in the population.

During the sampling of heterogeneous mixtures of particles, the variance of the sampling error is generally non-zero.

Pierre Gy derived, from the Poisson sampling model, the following formula for the variance of the sampling error in the mass concentration in a sample:

V = \frac{1}{(\sum_{i=1}^N q_i m_i)^2} \sum_{i=1}^N q_i(1-q_i) m_{i}^{2} \left(a_i - \frac{\sum_{j=1}^N q_j a_j m_j}{\sum_{j=1}^N q_j m_j}\right)^2 .

in which V is the variance of the sampling error, N is the number of particles in the population (before the sample was taken), q i is the probability of including the ith particle of the population in the sample (i.e. the first-order inclusion probability of the ith particle), m i is the mass of the ith particle of the population and a i is the mass concentration of the property of interest in the ith particle of the population.

It must be noted that the above equation for the variance of the sampling error is an approximation based on a linearization of the mass concentration in a sample.

In the theory of Gy, correct sampling is defined as a sampling scenario in which all particles have the same probability of being included in the sample. This implies that q i no longer depends on i, and can therefore be replaced by the symbol q. Gy's equation for the variance of the sampling error becomes:

V = \frac{1-q}{q M_\text{batch}^2} \sum_{i=1}^N m_{i}^{2} \left(a_i - a_\text{batch} \right)^2 .

where abatch is the concentration of the property of interest in the population from which the sample is to be drawn and Mbatch is the mass of the population from which the sample is to be drawn.

From Yahoo Answers

Question:Can you also give some examples of mixtures which can be separated through evaporation? I'm kind of confused.

Answers:identification.. basically you can use evaporation to differentiate between products by boiling points. an example of this could be any organic compound of different functional groups, they usually have different physical characteristics. (benzoic acid has a bp of ~249 C and ethanol has a bp of about 78 C, something that could easily be separated using a rotary evaporator or simple distillation)

Question:What is an example of a mixture that can be separated by filtration?

Answers:salt..and mixture that have different boiling points

Question:i have a science project that i have to do on separating mixtures in every day life, ex. oil spills from water. i want to do something somewhat original, and i have no ideas! if you guys have any ideas, it would be a big help! thanks!

Answers:well here are some mixtures which are separated in other fields...... In cooking, you normally skim off the oil/fat from the gravy or broth In cooking, you sometimes need to separate the egg yolk from the egg white to make meringues YUM In gas tanks, if water separates out from the gasoline (or too much water is in the gas tank) it will separate out and cause the car starting problems. Why they add gasoline additives in (methanol or ethanol) to prevent this, especially in cold weather. we all separate recyclables for collection (well we should).. consider cooking as a way into a different part of chemistry.:) just a thought

Question:Okay, can you give me a few examples?? I already know sand and water and stuff, but what are other examples that dont use water?? Help please? Thanks

Answers:milk and cookies syrup and oil

From Youtube

Mixtures :Teachzer.com - This video discusses the differences between mixtures and compounds. It also goes through the different methods in separating mixtures into the individual substances.

Sublimation Process - A Chemistry Phenomenon :www.SimpleChemConcepts.com Welcome to www.SimpleChemConcepts.com. You have learnt about the 3 States of Matter - Solid, Liquid & Gas. We have also learnt about the physical processes that changes one state to another. eg Melting, Evaporation, Boiling, Condensation, Freezing, etc.. Sublimation is a very special process which changes the solid state directly into the gaseous state without going through Melting process (ie without going through the liquid state). In this video, we share with you one of the everyday life examples that such Chemistry Phenomenons are observed. This is Solid Carbon Dioxide, and in general we call it as Dry Ice. Dry Ice is a classic example that we observe sublimation process to occur. The solid carbon dioxide changes directly into gaseous carbon dioxide, without going through the liquid state. Dry Ice is commonly used to keep Ice-Cream cold and solid by ice-cream vendors. Do you have any idea why we don't use normal ice (made of water) to keep ice cream cold? For more Chemistry Tips, Strategies & Phenomenons, please visit us at www.SimpleChemConcepts.com