Is urea dangerous in a cold pack?
In cold packs is usedAmmonium nitrate.
It's dangerous because it can explode. But for this it must be absolutely dry.
In a cold pack it is in a water solution. Nevertheless you shouldn't eat it or contact it a long time with your skin. In case of a damage of the cold pack you can just wash it away with water.
Explain which type of reaction exothermic or endothermic would be required to make a cold and a cold pack or hot pack?
Examples include Urea [CO(NH2)2], Potassium Nitrate [KNO3] and Ammonium Nitrate [NH4NO3]. All are commonly found in "Instant cold packs" that become cold when you rupture the inner bag by depressing the pack gently but firmly. When then inner water makes contact with the chemicals listed above inside the outer bag of the pack, the endothermic reaction begins. This is the source of the cold temperature these types of Instant Cold Packs produce.
A cold pack creates a endothermic reaction when the chemical reacts, which means that energy is taken from the surrounding, which makes the packaging cold. it is the opposite with a heat pack, an exothermic reaction is created which releases the energy into the surrounding creating the heat. Hope this helped.
Instant cold packs use water and ammonium nitrate. The ammonium nitrate is a powder found inside the cold pack, and the water is inside a plastic container inside the cold pack. When the plastic container containing the water is broken and mixed with the ammonium nitrate, the water dissolves the ammonium nitrate, which is overall an endothermic reaction, causing the cold pack to get cold.