Give two reasons to justify (a) Water at room temperature is a liquid (b) An iron almirah is a solid at room temperature

The explanation to the question is:

(a) Water is a liquid at room temperature due to its molecular structure and boiling/freezing points (0°C-100°C).

(b) An iron almirah is solid at room temperature because iron has a high melting point (1,538°C) and strong atomic bonding.

Complete Answer:

(a) Water at room temperature is a liquid:

1. Molecular structure: Water has a molecular structure where hydrogen bonds hold the molecules together but not too tightly, allowing them to move around each other. This gives water fluidity, making it a liquid at room temperature.
2. Boiling and freezing points: Water’s boiling point is 100°C, and its freezing point is 0°C, both of which fall within the typical room temperature range (around 20-25°C), keeping it in a liquid state.

(b) An iron almirah is a solid at room temperature:

1. High melting point: Iron has a high melting point of 1,538°C, which is far above room temperature. As a result, iron remains solid at typical room temperature.
2. Strong atomic bonding: The strong metallic bonds between iron atoms hold them in a rigid structure, which prevents the material from becoming a liquid at room temperature.

What is Boiling Point?

The boiling point is the temperature at which a liquid turns into a gas (vaporises) throughout the entire liquid. This occurs when the liquid’s vapour pressure equals the external pressure acting on it.

Process of Boiling Point:

• As heat is applied to a liquid, its molecules move faster, increasing the vapour pressure.
• When this vapour pressure equals the surrounding atmospheric pressure, the liquid begins to boil.

Factors Influencing Boiling Point:

• External Pressure: At higher altitudes, the atmospheric pressure is lower, so liquids boil at lower temperatures. At sea level (1 atm), water boils at 100°C, but at higher elevations, it boils at lower temperatures.
• Intermolecular Forces: Liquids with stronger intermolecular forces (e.g., hydrogen bonds in water) have higher boiling points because more energy is needed to break these forces.

Examples:

• Boiling point of Water: 100°C at 1 atm pressure.
• Boiling point of Mercury: 356.7°C at 1 atm pressure.

What is Melting Point?

The melting point is the temperature at which a solid turns into a liquid. It is the temperature where the solid and liquid phases of a substance are in equilibrium under a given pressure.

Process of Melting Point:

• As heat is applied to a solid, its molecules gain kinetic energy, causing them to vibrate more intensely.
• At the melting point, these vibrations become strong enough to overcome the intermolecular forces that hold the molecules in place, causing the solid to melt into a liquid.

Factors Influencing Melting Point:

• Pressure: For most substances, increasing pressure raises the melting point, but there are exceptions (e.g., ice melts at a lower temperature under high pressure).
• Intermolecular Forces: Substances with stronger intermolecular forces (e.g., ionic bonds in salts or metallic bonds in iron) have higher melting points because more energy is required to break the bonds.

Examples:

• Melting point of Water: 0°C (solid to liquid transition).
• Melting point of Iron: 1,538°C (solid to liquid transition).

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