32. State Symbols & Predicting States of Matter

1. The Four State Symbols

In chemical equations, state symbols show the physical state of each substance:

  • (s) stands for Solid (e.g., metals like Sodium at room temperature).

  • (l) stands for Liquid (e.g., pure water).

  • (g) stands for Gas (e.g., hydrogen gas given off in a reaction).

  • (aq) stands for Aqueous (meaning the substance is dissolved in water).

2. Predicting States of Matter

To predict the state of a substance at a specific temperature, you compare that temperature to its melting point and boiling point:

  • Solid: The temperature is below the melting point.

  • Liquid: The temperature is between the melting point and the boiling point.

  • Gas: The temperature is above the boiling point.

3. Example Predictions (at 800°C)

Using a number line for temperature can help visualize where a substance sits:

Substance

Melting Point

Boiling Point

State at 800°C

Reason

Water

0°C

100°C

Gas

800°C is well above the boiling point.

Magnesium

650°C

1107°C

Liquid

800°C is between the melting and boiling points.

Copper

1083°C

2562°C

Solid

800°C is below the melting point.

4. Summary Checklist

  • Check the state symbols in equations to understand how substances are behaving (e.g., if a solid is dissolving to become aqueous).

  • Use data tables provided in exams to identify the melting and boiling points before making a prediction.