They are more firm and hold their shape when cooked. Kala chana does not get mushy when boiled and takes longer to cook. It is always best to soak chickpeas overnight  This removes the indigestible sugars and reduces flatulence. Wash the chickpeas and change the water 2-3 times while soaking if possible. Always soak chickpeas in lot of water as they double in size. Merely just enough water for the beans to expand will simply dry out the top layer and result in uneven soaking and affect cooking later. Uniformly soaked beans is very important in the preparation of this recipe.