A man started working in a factory where he needed to deal with steam and boiling water regularly. On the firs

Question

A man started working in a factory where he needed to deal with steam and boiling water regularly. On the first day, his doctor warned him to be more careful of the steam because burns caused by steam can be more severe than that of hot water. What is the reason behind this?

Examoogle · Accepted Answer

The correct answer is Option C: Steam has more latent heat of vaporisation. Steam causes more severe burns than boiling water because it contains significantly more heat energy at the same temperature ($100^{\circ}	ext{C}$). This extra energy is known as the latent heat of vaporisation, which is released when steam condenses into liquid water on the skin.

Step-by-Step Solution & Concepts:
Steam causes more severe burns than boiling water because it contains significantly more heat energy at the same temperature ($100^{\circ}	ext{C}$). This extra energy is known as the latent heat of vaporisation, which is released when steam condenses into liquid water on the skin.

Working Principle: When water boils, it absorbs energy to break intermolecular hydrogen bonds without increasing in temperature. This energy, the latent heat of vaporisation ($L_v \approx 2260 	ext{ kJ/kg}$), is stored in the steam. Upon contact with the cooler skin, steam condenses into liquid water, releasing this substantial amount of latent heat directly onto the surface of the skin.

Key Formulas: $Q = m 	imes L_v$ — where $Q$ is the total heat released, $m$ is the mass, and $L_v$ is the latent heat of vaporisation

Key Points: Boiling water and steam are both at $100^{\circ}	ext{C}$ at standard atmospheric pressure.; The phase change from gas to liquid releases $2260 	ext{ J/g}$ of energy.; Skin damage is proportional to the total energy transferred to the tissue.; Steam provides both sensible heat (from cooling) and latent heat (from condensation).

Applications: Steam sterilisation in autoclaves; Steam engines and industrial turbines

Additional Info: The latent heat of vaporisation for water is approximately $2.26 	imes 10^6 	ext{ J/kg}$.. Option A and B are incorrect as they relate to sensory perception, not the thermodynamic energy transfer mechanism causing injury.

Answer: C is correct — Steam releases a large amount of latent heat upon condensation, leading to deeper and more painful tissue damage compared to boiling water at the same temperature.

Exam Tip: Always remember that during phase changes, temperature remains constant, but the energy content changes significantly; this is a common theme in thermodynamics questions.

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Option A: Steam cannot be seen

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Option B: Steam is odourless

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Option D: Steam can remain stuck to the body

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