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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:This is just my guess. Could you please correct me if I'm wrong. Compound, homogeneous mixture, or heterogeneous mixture: Soil: homogeneous mixture. Sugar water: homogeneous mixture. Rocky road icecream: heterogeneous mixture. Alcohol: compound. Pure air: homogeneous mixture.

Answers:Soil is heterogeneous (not all the parts are the same, and there are many different parts) everything else is right :)

Question:If air is 78% nitrogen and about 21% oxygen, with the remaining 1% a mixture of various trace gases, then what is it? Can you please explain why it is a compound or homogeneous mixture or heterogeneous mixture.

Answers:It is strictly speaking a heterogeneous mixture as water vapour and dust particles are also part of it.

Question:please explain why so i can understand. i'll write what after ~ gasoline ~ homogeneous mixture because only one phase/layer a stream bed with gravel at the bottom ~ ? air ~ heterogeneous because dust is also in air? brass ~ pure substance because it's an element? copper metal ~ heterogeneous..its a guess the pages in your textbook ~ homogeneous..another guess sorry i left out a part i meant: i'll write what i think after the ~

Answers:gasoline--homogeneous mixture with octane, toluene, benzene, xylene, propyl amine, etc. stream bed with gravel--heterogeneous mixture multiple phases (liquid, solid) air--good brass -- not an element homogeneous mixture of copper and zinc copper--pure substance pages-- homogeneous

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From Youtube

Heterogeneous and Homogeneous Mixture :Making strawberry milk (homogeneous mixture) and bowl of M&Ms (heterogeneous mixture).