Which Statement Describes a Chemical Property of Water?
A chemical property refers to a characteristic of a substance that becomes evident during a chemical reaction. It describes the substance’s ability to change into a different substance through chemical processes. Unlike physical properties, which include traits like color, boiling point, or density, chemical properties involve how a substance reacts with other substances.
Examples of Chemical Properties of Water:
- Reactivity with metals: Water reacts with certain metals, such as sodium (Na), to form a metal hydroxide and hydrogen gas.
Example Reaction:
2Na+2H2O→2NaOH+H22Na + 2H_2O \rightarrow 2NaOH + H_22Na+2H2O→2NaOH+H2
- Electrolysis of water: Water can decompose into hydrogen gas (H₂) and oxygen gas (O₂) when an electric current is passed through it.
Example Reaction:
2H2O→2H2+O22H_2O \rightarrow 2H_2 + O_22H2O→2H2+O2
- Neutral pH (in pure form): Water can act as both an acid (donating H⁺ ions) and a base (accepting H⁺ ions) in chemical reactions, showing amphoteric behavior.
Example Reaction (acidic behavior):
H2O+NH3→NH4++OH−H_2O + NH_3 \rightarrow NH_4^+ + OH^-H2O+NH3→NH4++OH−
- Ability to dissolve substances (solvent properties): Chemically, water can interact with ionic or polar substances, forming hydration shells around ions. This property makes it a “universal solvent.”
Primary Chemical Property of Water:
Water’s ability to react chemically with other substances, such as undergoing electrolysis or reacting with metals, represents its chemical properties. This contrasts with physical properties, such as its freezing point (0°C) or boiling point (100°C).
Incorrect Examples (Physical Properties):
- Water is colorless and odorless.
- Water freezes at 0°C.
- Water boils at 100°C under standard pressure.
Final Note:
To identify a chemical property of water, look for statements that describe how water reacts or changes at the molecular level. Statements about appearance or state changes involve physical properties, not chemical ones.
