Question

The table below gives some experimental results on four samples of water. Use the information to answer the questions that follow.

	Drops of soap needed to form lather
Sample of water (50cm2)	Before boiling	After boiling
A	25	15
B	8	8
C	18	8
D	25	25

1. Which sample(s) contain permanent hardness? Explain. 
2. Which samples are likely to contain calcium hydrogen carbonate? Explain.  

Answer 1

1. B and D
   The drops of soap needed to form lather remain the same/did not change even after boiling.
2. A and C
   The drops of soap needed to form lather decreased after boiling.