SPM Physics: AHA! Heat Transfer – When c Cancels Out!

 

In heat transfer questions, students often panic when the specific heat capacity (c) is not given. But here’s the trick:

• If the substances are the same, their c values cancel out.

• Heat gained = Heat lost.

• Example: Mixing 450 g of water at 30°C with m g of hot water at 100°C, final temperature 70°C.

Calculation:

$$450c(70-30)=mc(100-70)$$

Cancel c:

$$450(40)=m(30)$$

$$m=600g$$

Answer: 600 g

But if the substances are different (e.g. glass + water), you cannot cancel c. You must use the given specific heat capacities.

AHA! Cancel c, secure marks. Not by sight, but by INSIGHT!

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