Identify the pure substances and mixture from the following list : (a) solid common salt (b) milk (c) air (d) oxygen (e) fruit juice (f) brass (g) copper sulphate crystals (h) distilled water (i) sugar solution (j) honey (k) Ice cream (l) Iron sulphide
The Correct Answer and Explanation is:
Let’s break down the list and identify each substance as either a pure substance or a mixture.
Pure Substances:
- Solid common salt (a): This is a pure substance. Sodium chloride (NaCl) is a compound consisting of only one type of molecule.
- Oxygen (d): This is a pure substance. Oxygen (O₂) is a diatomic molecule made up of oxygen atoms, and it is chemically pure.
- Copper sulphate crystals (g): Copper sulfate (CuSO₄) is a pure compound. The crystals contain only copper, sulfur, and oxygen atoms in a fixed ratio.
- Distilled water (h): Distilled water is a pure substance. It is composed only of H₂O molecules, with no impurities or dissolved substances.
- Iron sulphide (l): Iron sulfide (FeS) is a pure compound, composed of iron and sulfur in a fixed ratio.
Mixtures:
- Milk (b): Milk is a mixture. It contains water, fats, proteins, and various other compounds that are not chemically bonded, and the composition can vary.
- Air (c): Air is a mixture. It is composed of several gases like nitrogen, oxygen, carbon dioxide, and trace gases in varying proportions.
- Fruit juice (e): Fruit juice is a mixture. It contains water, sugars, acids, vitamins, and other compounds extracted from fruits.
- Brass (f): Brass is a mixture. It is an alloy made of copper and zinc, and its composition can vary.
- Sugar solution (i): Sugar solution is a mixture. It consists of sugar dissolved in water, and the sugar molecules are not chemically bonded to the water molecules.
- Honey (j): Honey is a mixture. It consists of sugars, water, and other compounds like enzymes, amino acids, and minerals.
- Ice cream (k): Ice cream is a mixture. It contains water, fat, air, sugar, and other ingredients like flavorings and stabilizers, all physically combined.
Explanation:
- Pure substances are materials with a constant composition and specific chemical properties. They can either be elements or compounds. For instance, oxygen (O₂) is an element, while copper sulfate (CuSO₄) and solid salt (NaCl) are compounds.
- Mixtures consist of two or more pure substances that are physically combined, and their composition can vary. They don’t have a fixed ratio, and the individual substances retain their properties. For example, milk and fruit juice contain various components like water, fats, proteins, and sugars that are not chemically bonded.
In summary:
- Pure substances: Solid common salt, oxygen, copper sulfate crystals, distilled water, iron sulfide.
- Mixtures: Milk, air, fruit juice, brass, sugar solution, honey, ice cream.
