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From Wikipedia

Mixture

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.


Mixture

In chemistry, a mixture is a material system made up by two or more different substances which are ( mix ed) 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


From Yahoo Answers

Question:For example, could it be used to separate sand from water? Please explain. #2 - Could distillation be used to separate the components of a solution made by mixing 2 liquids? For example, could it be used to separate alcohol from water? Please explain! Thank you!!

Answers:1: Yes, the mixture of sand and water can be heated to drive off the water as vapour. If the water is required, the process can be carried out as a simple distillation process where the separated water vapour (steam) can be recondensed. (The easiest way is to filter the sand out of the mixture and dry it). 2: Alcohol and water solution (mixture) can also be separated by the same process according to the difference in the boiling temperatures of the alcohol and water. (This is the process used to produce Ethanol (drinking alcohol) from a fermented sugar solution) The temperature of the system must be carefully controlled at the boiling temperature of the lightest component by a 'Reflux System' which will condense and return heavier vapour from the distillate to the distillation flask. The rest of the vapour, high in the lighter fraction, goes on to the condensation and recovery stage. For purity, the condensate should be re-distilled 2 or 3 times.

Question:In a chemistry sense. Creamy peanut butter, not chunkY!

Answers:Peanut butter by itself without any stabilizers is a heterogeneous mixture. Most peanut butter you buy today has trans fatty oils added to it to keep it from separating, in which case it is homogeneous. If it didn't have the trans fats, the peanut oil would float to the top and you'd have to keep mixing it up/

Question:Figure out if they are homogeneous or heterogeneous mixtures. When substance X and Y are mixed, a magnet can remove particles of substance X that are viable to the naked Eye...heter or homogeneous? why? partivles of substance B are permanently suspended but not dissolved in substance T. homo or heterogeneous? why? THANKS!

Answers:HOMOgeneous = a mixture that is the same (uniform) throughout. It must be chemically uniform and consist of only one phase. HETEROgeneous = a mixture that has separate parts. A magnet can remove particles of substance X that are visible to the naked eye = HETEROgeneous, because the mixture has visibly different components, X and Y, which can be separated simply by non-chemical means. Particles of substance B are permanently suspended but not dissolved in substance T = HETEROgeneous again. Although particles of B are suspended in substance T, they are NOT dissolved, therefore B is still in solid phase. Since this mixture is NOT a solution, it is not chemically uniform so does not have uniform composition of its particles (the distinct particles do not exhibit a definite proportion to each other).

Question:(1) - A colorleess, single- phase liquid leaves behind a solid white residue when boiled away ( evaporated). (2) A uniform red liquid with a boiling point of 59 celcius that cannot be broken down into simpler substances using chemical means. (3) A "cloudy" liquid that separates into two layers upon standing for two hours. (4) A green solid, all of which melts at the same temperature to produce a liquid that decomposes upon further heating. Also what arrangement do Elements 56, 74, and 82 belong to on the perodic table .? 10 points for best answer

Answers:1) Homogenous mixture (solution) The solvent was evaporated and the solute remained behind. 2) Element The definition of an element is a material that cannot be broken down into simpler substances by chemical means. 3) Heterogeneous mixture (suspension) A suspension is made with large solute particles which settle out of solution after a period of time and must be shaken or stirred to remix the particles. 4) Compound A compound has a definite melting point and may decompose upon further heating. Element 56 (Barium), 74 (Tungsten), and 82 (Lead) are all found in period - or series - 6 of the periodic table. That means they all have 6 electron levels with their valence electrons occupying level six.

From Youtube

Separating Mixtures :

Homogenenous and Heterogeneous Mixtures :A video describing the differences between Homogenenous and Heterogeneous Mixtures.