Question

How much energy is released or absorbed when 1 gm of water at 0° C freezes to ice at 0° C?

Answer 1

In CGS system :

Mass of water = m = 1 gm 

Latent heat of fusion of ice (L) = 80 cal/gm 

The energy transferred or released when 1 gm of water at 0° C freezes to ice at 0° C. 

Q = mL_freeze = 1 × 80 = 80 Cal.

(OR) 

In SI system : 

Mass of water = m = 1 gm = 1/1000 kg

Latent heat of fusion = L = 3.36 × 10⁵ J/kg.

Amount of heat released or transferred when lgm of water at 0°C freezes to ice at 0°C.

Q = mL_fusion = 1/1000 kg × 3.36 × 10⁵ = 3.36 × 10² = 336J.

(OR) 

In CGS system : 

Mass of water = m = 1 gm 

Latent heat of fusion of ice (L) = 80 cal/gm

The energy transferred or released when 1 gm of water at 0° C freezes to ice at 0°C. 

Q = mL_freeze = 1 × 80 – 80 cal. 

(Or) 

In SI system : 

In SI, Q = 80 × 4.2 [1 cal = 4.2 J] 

Q = 1 x 10^-3 × 3.36 × 10⁵ = 3 36 J.