Sodium ............... reacts smoothly with cold water.

Answer

To solve the question "Sodium ............... reacts smoothly with cold water," we need to fill in the blank with the appropriate term that describes sodium's behavior in this context.

### Step-by-Step Solution:

1. **Identify the Element**: The question mentions sodium, which is represented by the symbol Na and has an atomic number of 11. Sodium is classified as an alkali metal.

**Hint**: Remember that sodium is part of the alkali metals group in the periodic table.

2. **Understand Reactivity**: Sodium is known for its high reactivity, especially with water. It is positioned high on the reactivity series, just below potassium, indicating that it reacts vigorously with water.

**Hint**: Consider the properties of alkali metals and their tendency to react with water.

3. **Chemical Reaction**: When sodium reacts with cold water, it produces sodium hydroxide (NaOH) and hydrogen gas (H₂). The reaction is as follows:
\[ 2 \text{Na} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2 \]
This shows that sodium reacts smoothly and quickly with water, forming a base and releasing hydrogen gas.

**Hint**: Recall the products of the reaction between sodium and water.

4. **Fill in the Blank**: Given that sodium is a metal and it reacts smoothly with cold water, the appropriate word to fill in the blank is "metal." Thus, the complete statement will be:
"Sodium metal reacts smoothly with cold water."

**Hint**: Think about the classification of sodium and how it interacts with water.

### Final Answer:
Sodium metal reacts smoothly with cold water.