Classify each of the following as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: (a) seawater, (b) helium gas, (c) sodium chloride (salt), (d) a bottle of soft drink, (e) a milkshake, (f) air in a bottle, (g) concrete.

(a) Homogeneous mixture.

(b) Element.

(c) Compound.

(d) Homogeneous mixture.

(e) Homogeneous or heterogeneous depending on the milkshake type.

(f) Homogeneous mixture.

(g) Heterogeneous mixture.

Explanation:

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In this case, one must remember that elements stand for single atoms of one particular element from the periodic table, compounds are constituted by two or more different bonded elements, homogeneous mixtures are substances composed by two or more indistinguishable elements and/or compounds and heterogeneous mixtures are substances composed by two or more distinguishable elements and/or compounds. In such a way:

- Seawater is clear but it has water and other dissolved minerals, therefore, one states that it is an homogeneous mixture.

- Helium gas stands for a single atom of helium since it is monoatomic, therefore it is an element.

- Sodium chloride is a compound constituted by one atom of chlorine and one atom of sodium chemically bonded.

- The bottle of soft drink could be a homogeneous mixture since it has no distinguishable particles.

- The milkshake could be either homogeneous or heterogeneous depending on the shaking degree, there are some milkshakes that are just liquid, but there are others that have some toppings which make them heterogeneous.

- The air in a bottle is a homogeneous mixture since air is majorly composed by nitrogen (79%) and oxygen (20%), the rest are other gases such as methane, carbon dioxide, hydrogen, argon and others as traces.

- The concrete is a heterogeneous mixture constituted by cement, water, fine aggregates and coarse aggregates.

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An element is defined as a substance that contains same type of atoms which cannot be broken down into simpler substances.

A compound is defined as a substance that contains more than two different atoms in a fixed ratio by mass. Elements of a compound are chemically combined together.

A homogeneous mixture is defined as a mixture in which solute particles are uniformly distributed into the solvent.

Whereas a heterogeneous mixture is defined as a mixture in which solute particles are non-uniformly distributed in a solvent.

In both homogeneous and heterogeneous mixture there is no chemical combination between solute and solvent particles.

Hence, the given species are classified as follows.

(a) Sea water : It contains decays of dead plants and animals. As a result, these are suspended into the water. Hence, sea water is a heterogeneous mixture.

(b) Helium gas : It contains only atoms of helium. Hence, it is an element.

(c) Sodium chloride (salt) : It is a compound in which sodium and chlorine atoms are present in 1:1 ratio.

(d) A bottle of soft drink : As soft drinks contain a clear solution with no suspended particles. Hence, it is a homogeneous mixture.

(e) a milkshake : It contains different elements which are evenly distributed in the milk. Hence, milk shake is a homogeneous mixture.

(f) air in a bottle : As air in a bottle will not contain any smoke or fog. So, there will be even distribution of all the gases present in air. Hence, it is a homogeneous mixture.

(g) concrete : It contains cement, fine aggregates, coarse aggregates, water and other particles that are not evenly distributed. Hence, concrete is a heterogeneous mixture.