How does adding salt in the ice cap help in dry cold application?

Appeared in: AIIMS Raipur NO- 2019 (shift 3rd)

Explanation

Adding salt to ice causes a phenomenon called freezing point depression.
The salt disrupts the crystal structure of the ice, forcing it to melt at a temperature below the usual 0°C (32°F).
This process allows the ice-salt mixture to become significantly colder than ice alone, enhancing the therapeutic cooling effect.
The melting process itself is endothermic, meaning it absorbs a large amount of heat from the patient's body, providing potent cooling.

Option A: The ability to mould an ice pack is primarily determined by using crushed ice and not overfilling the bag, which allows it to conform to body contours.
Option B: This describes the result or outcome of adding salt, not the underlying physical mechanism. The question asks 'how' the effect is achieved.
Option C: This is scientifically incorrect. Adding a solute like salt to a solvent like water always lowers the freezing/melting point, it never increases it.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The scientific principle behind using salt with ice for therapeutic cold application as background academic context rather than a clinical decision trigger.
Understanding the principle of freezing point depression allows nurses to create more intense cold applications when clinically indicated, for example, to rapidly reduce severe swelling.
Nurses must be aware that because a salt-ice mixture is colder than 0°C, the risk of frostbite and skin damage is significantly higher. Extra vigilance and protective barriers are essential.
What if? If the goal was gentle, prolonged cooling for a sensitive area, the nurse should not add salt. Using plain crushed ice would provide cooling at 0°C, reducing the risk of tissue damage.

How to Approach the Question

First, identify the core of the question: it's asking for the scientific mechanism ('how') behind a specific nursing action (adding salt to an ice pack).
Recall or deduce the basic physics/chemistry principle involved. What happens when you mix salt and ice? This relates to colligative properties, specifically freezing point depression.
Evaluate the options based on this principle. Option A (moulding) is about physical preparation, not chemistry. Option C (increases melting point) is scientifically false.
Differentiate between the mechanism and the result. Option D ('Lowers melting point') is the direct mechanism. Option B ('Provide more cooling') is the therapeutic result of that mechanism. Since the question asks 'how', the mechanism is the more precise and correct answer.

Concept Tested & Keywords

Concept Tested: The scientific principle behind using salt with ice for therapeutic cold application.
Stem keywords: salt, ice cap, dry cold application
Lead-in keywords: How

QN3Xrp05nWlQL-AeJqyK9Z

E6 Nursing Fundamentals Potter Perry 12e Part 6 p. 106-108

Practise the full AIIMS Raipur NO- 2019 (shift 3rd)

Attempt every question from this paper in a timed mock, then review the full solution for each one.