Question

four properties of water are listed.

1. it has high thermal conductivity.
2. it reacts with metals to form metal hydroxide and hydrogen gas.
3. when heated to 100 °c, water evaporates.
4. it decomposes to form hydrogen and oxygen.

which are the chemical properties of water?

1 and 2
1 and 3
2 and 3
2 and 4

Explanation:

Define physical and chemical properties

To solve this, we must distinguish between Physical Properties and Chemical Properties. A physical property is a characteristic that can be observed or measured without changing the substance's chemical identity. A chemical property describes the ability of a substance to undergo a specific chemical change, transforming into one or more entirely new substances.

Analyze properties 1 and 3

Let's evaluate the first and third statements:

• Property 1 (Thermal conductivity): This measures how well a substance transfers heat. Observing heat transfer does not alter the chemical composition of water. Therefore, this is a Physical Property.
• Property 3 (Evaporation at \(100\text{ }^\circ\text{C}\)): Evaporation is a phase transition from liquid to gas. The molecules remain \(H_2O\) throughout the process. Since no new substance is formed, this is a Physical Property.

Analyze properties 2 and 4

Now let's evaluate the second and fourth statements:

• Property 2 (Reaction with metals): This describes water reacting with metals to produce new substances (metal hydroxide and hydrogen gas). Because the chemical identity changes, this is a Chemical Property.
• Property 4 (Decomposition): This describes water breaking down chemically into its constituent elements, hydrogen gas and oxygen gas. Since new substances are formed, this is a Chemical Property.

Identify the correct option

Statements 2 and 4 describe chemical properties of water. Looking at the choices:

• 1 and 2
• 1 and 3
• 2 and 3
• 2 and 4

The correct option is "2 and 4".

Answer:

• 1 and 2
• 1 and 3
• 2 and 3
• 2 and 4 (Correct answer)