Question

Pick the false statement on specific heat

• A. Its value is same for all the substances
• B. Its S.I. unit is J/kg-K
• C. Its value is high when the rate of rise (or fall) of temperature is low
• D. Its value for water is 1 cal/g-ºC

Answer 1

The Correct Option is A

The specific heat is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius (or Kelvin). It is a property that varies from one substance to another, meaning different substances require different amounts of heat to change their temperatures by the same amount. Hence, the statement "Its value is the same for all the substances" is false.

The other statements about specific heat are true:

• Its S.I. unit is J/kg-K. This is indeed correct as specific heat is measured by the amount of heat needed per kilogram of a substance per degree Kelvin.
• Its value is high when the rate of rise (or fall) of temperature is low. This is accurate because substances with high specific heat tend to change temperature slowly since they require more heat for the same temperature change.
• Its value for water is 1 cal/g-ºC. This is true for water, having one of the highest specific heat values, specifically 1 calorie per gram per degree Celsius, equivalent to 4.186 joules per gram per Celsius.

Therefore, the false statement is the first one, as specific heat indeed differs among various substances.

Answer 2

Concept: Specific heat is the amount of heat required to raise the temperature of 1 kg of a substance by 1 K.

Let’s evaluate each statement: 

• Its value is same for all the substances – False: Different substances have different specific heat capacities.
• Its S.I. unit is J/kg-K –  True.
• Its value is high when the rate of rise (or fall) of temperature is low –  True: Substances that heat up or cool down slowly have high specific heat.
• Its value for water is 1 cal/g-ºC –  True.

Final Answer: The false statement is: "Its value is same for all the substances"