Calcium oxide and calcium hydroxide are two common chemical substances that have significant differences in chemical properties, physical properties, and application fields.

From a chemical perspective, calcium oxide is an alkaline oxide with the chemical formula CaO, while calcium hydroxide is a strong base with the chemical formula Ca (OH) ₂. The difference in properties between these two substances is that calcium oxide can undergo a neutralization reaction with acid, generating salt and water; Calcium hydroxide can also undergo neutralization reactions with acids, but can also react with some non-metallic oxides to form salts and water. In addition, calcium hydroxide also has some special properties, such as its ability to react with carbon dioxide to form calcium carbonate precipitate, which is the basis for many industrial applications.

From a physical perspective, calcium oxide is a white solid that is insoluble in water but can react with water to form calcium hydroxide; Calcium hydroxide is a white powder that is slightly soluble in water, and its aqueous solution is alkaline. In addition, the solubility of calcium hydroxide decreases with increasing temperature, which is also an important characteristic in its application field.

From the perspective of application fields, both calcium oxide and calcium hydroxide have a wide range of applications. Calcium oxide is mainly used to prepare calcium hydroxide, calcium salts, calcium bricks, etc. It can also be used as a desiccant, water absorbent, analytical reagent, etc; Calcium hydroxide is mainly used in fields such as water treatment, building materials, and chemical industry. For example, calcium hydroxide can be used as a water purifier to remove suspended solids and heavy metal ions from water; In the field of construction, calcium hydroxide can be used to prepare gypsum boards, coatings, adhesives, etc; In the chemical industry, calcium hydroxide can be used as a catalyst, neutralizer, etc.

In summary, although both calcium oxide and calcium hydroxide are compounds of calcium, they have significant differences in chemical properties, physical properties, and application fields. Understanding these differences helps us better understand and apply these two chemical substances.