Which of the following properties of sodium metal is a chemical property?

• A. It is silvery in appearance.
• B. It has a melting point of 98 °C.
• C. It is soft enough to be cut with a knife.
• D. It reacts vigorously with water to produce hydrogen gas.

Answer: (D)

Verified step by step guidance

1. Understand the difference between physical and chemical properties: Physical properties can be observed or measured without changing the substance's identity, while chemical properties describe how a substance interacts with other substances, leading to a change in its chemical composition.
2. Examine each property given: 'Silvery in appearance,' 'melting point of 98 °C,' and 'soft enough to be cut with a knife' are all physical properties because they describe observable traits or physical behavior without altering the substance's identity.
3. Identify the property that involves a chemical change: 'Reacts vigorously with water to produce hydrogen gas' describes a chemical reaction where sodium metal changes into new substances (sodium hydroxide and hydrogen gas), indicating a chemical property.
4. Recognize that chemical properties are often revealed through reactivity or the ability to undergo chemical changes, such as reactions with water, acids, or oxygen.
5. Conclude that the property involving reaction with water is the chemical property because it describes sodium's behavior in a chemical reaction, unlike the other physical characteristics.