 Dissolving ammonium chloride in water is an endothermic process. We'll place a small amount of water onto a wooden block. We'll place the beaker of water onto the wooden block. We will add the ammonium chloride to the beaker and stir. As the ammonium chloride dissolves, the temperature of the water decreases. It is an endothermic process. Eventually the temperature gets cold enough to solidify the water under the beaker. We will pick up the beaker and the wooden block.