Question

When lemonade (an acid) is mixing with baking soda (a base), they react and make a new substance. The new substance is cold to the touch, heatis being absorbed by the substance, and the temperature has gone down.

Answer 1

When we are talking of chemical reactions we have those that absorb heat and those that expel heat, in the first case are called endothermic reactions, and in the second case exothermic reactions. Therefore in the present example is an endothermic reaction because the product of lemon-baking soda is cold, meaning that absorbs heat.