Matter In Our Surroundinges — Important Questions

A pure substance made from two or more elements chemically combined

A compound is formed when two or more elements chemically combine in a definite proportion. Step 1: Elements must be chemically bonded together, not just mixed physically. Step 2: The elements combine in a fixed ratio by mass (definite proportion). Step 3: The compound has different properties from the individual elements. Step 4: For example, water (H2O) is a compound of hydrogen and oxygen with completely different properties. Step 5: Mixtures are not compounds as components retain individual properties.

Evaporation

Evaporation is the best method to separate salt from salt water. Step 1: Salt water is a homogeneous solution where salt is completely dissolved. Step 2: When heated, water evaporates and turns into water vapor. Step 3: Salt has a much higher boiling point than water, so it remains behind as solid crystals. Step 4: This method recovers the salt in solid form while water vapor can be condensed if needed. Step 5: Other methods won't work as salt is completely dissolved and not magnetic.

Water

In a sugar solution, water is the solvent and sugar is the solute. Step 1: A solution has two components - solute and solvent. Step 2: The solute is the substance that gets dissolved (sugar in this case). Step 3: The solvent is the substance that does the dissolving (water in this case). Step 4: Generally, the component present in larger quantity is the solvent. Step 5: Water is called the universal solvent because it dissolves many substances.

Gas

Gases are highly compressible due to large spaces between particles. Step 1: In gases, particles are far apart with weak intermolecular forces. Step 2: Large spaces between particles allow them to be pushed closer together when pressure is applied. Step 3: This is why we can compress natural gas for CNG and cooking gas for LPG cylinders. Step 4: Solids and liquids have particles close together, making compression difficult. Step 5: This property of gases makes them useful for storage and transportation.