Why is the specific heat of water equal to unity,

2. Why is the specific heat of water equal to unity, that is, 1.0 cal/g-°C or
1.0 kcal/kg-°C?
3. Given that the specifi c heat of one material is twice that of another, compare the
relative amounts of heat required to raise the temperature of equal masses of
each material by 1 °C.
4. Say the same amount of heat was added to samples of the materials in Question 3,
and each sample had the same increase in temperature. Compare the relative
masses of the samples.
(

cal and kcal are obsolete units, you should be using joules.

The reason they equal (about) 1.0 is that that is the way the calorie was originally defined, as:

The small calorie or gram calorie (symbol: cal) approximates the energy needed to increase the temperature of 1 gram of water by 1 °C.

The term "approximately" is used because the amount of energy needed to increase the temperature of 1 gram of water by 1°C varies with the starting temperature. As a result there are many slightly different definitions of calorie.

3. it takes twice the energy for the first material.

4. The one with the lower SH would have to have twice the mass.