1. Chemical Tests for Water:Firstly, let's explore how we can detect the presence of water using chemical tests. Two common substances used for this purpose are anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate. When these compounds come into contact with water, they undergo specific chemical reactions that result in visible changes.Anhydrous cobalt(II) chloride, a pinkish compound, turns blue upon exposure to water. This color change occurs because cobalt(II) chloride forms a hydrated complex with water molecules. So, by observing the color change from pink to blue, we can confirm the presence of water.Similarly, anhydrous copper(II) sulfate, which is white in its dehydrated form, transforms into a blue hydrated form in the presence of water. This reaction is also a clear indicator of water's presence.2. Testing Water Purity:Now, let's discuss how we can assess the purity of water using its melting and boiling points. Pure substances have well-defined melting and boiling points, which serve as characteristic properties. By comparing the observed melting and boiling points of a sample of water with the accepted values, we can determine its purity.Impurities in water can alter its melting and boiling points. For instance, dissolved salts and minerals can elevate the boiling point and depress the melting point of water. Therefore, any deviation from the expected values may indicate impurities present in the water sample, thus affecting its purity.3. Distilled Water vs. Tap Water:In practical chemistry, distilled water is preferred over tap water due to its higher purity. Tap water often contains various chemical impurities such as dissolved minerals, organic compounds, and potentially harmful contaminants like chlorine or lead.Distilled water, on the other hand, undergoes a purification process where it is boiled and then condensed back into a liquid, leaving behind impurities. This results in water that is relatively free from contaminants, making it ideal for use in laboratory experiments where precise measurements and uncontaminated conditions are essential.