Which of the following is an example of a pure substance?a)Airb)Brassc)Waterd)MilkCorrect answer is option 'C'. Can you explain this answer?

Question

Answer

Air is a mixture of gases (mainly nitrogen and oxygen, plus others).

Brass is an alloy (a mixture of copper and zinc).

Milk is a colloid (a mixture of water, fats, proteins, etc.).

Water (H₂O) is a pure substance because it has a fixed chemical composition.

The answer is Water (C) because it’s made of only one kind of molecule, H₂O. The others are mixtures: air is gases, brass is metals, and milk is a colloid. That’s why water is the only pure substance here.

Answer

Answer: C. Water

Explanation: Water (H₂O) is a pure substance made up entirely of water molecules. Here are some key points:

Definition: A pure substance contains only one type of particle.
Composition: Water consists solely of H₂O molecules.
Characteristics: It has consistent properties throughout, such as boiling and freezing points.

Answer

We know that pure substances are made up of molecules of their own only.
air has nitrogen,oxygen,carbon dioxide,argon and traces of other gases
brass is an alloy made of more than 2 metals
milk is made up of many components like lactose, water milk solids

whereas:
water is only made up of hydrogen and oxygen
with uniformity all along
Making it classified as a pure substance

however it only holds true for pure,distilled water
all other waters have impurities.

Answer

Understanding Pure Substances
A pure substance is defined as a material that has a constant composition and consistent properties throughout. This means it contains only one type of particle, whether that be atoms or molecules.
Examples of Pure Substances
Here’s a breakdown of the options provided:

Air: This is a mixture of gases, primarily nitrogen and oxygen, along with other trace gases. Since it contains multiple components, it is not a pure substance.
Brass: This is an alloy made from copper and zinc. Since brass consists of two or more metals, it is also not a pure substance.
Water: This is a compound made up of two hydrogen atoms and one oxygen atom (H2O). It has a uniform composition and properties, making it a pure substance.
Milk: This is a complex mixture containing water, fats, proteins, lactose, and various vitamins and minerals. Because it has multiple components, it is not a pure substance.

Conclusion
Among the options, only water (option C) qualifies as a pure substance because it consists of a single type of molecule and maintains consistent properties. Understanding the difference between pure substances and mixtures is fundamental in chemistry, as it helps in identifying the nature of materials we encounter in daily life.

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