Baking soda and baking powder are both leavening agents used in baking to help baked goods rise, but they have different compositions and properties:

1. **Baking Soda (Sodium Bicarbonate)**:
- Baking soda is a chemical compound made of sodium bicarbonate.
- It requires an acidic ingredient, such as yogurt, buttermilk, vinegar, or lemon juice, to activate its leavening action.
- When combined with an acid, baking soda reacts to produce carbon dioxide gas, which causes dough or batter to rise.
- Baking soda reacts quickly, so it's important to bake the batter or dough immediately after mixing to avoid losing the leavening power.

2. **Baking Powder**:
- Baking powder is a mixture of baking soda, an acid (usually cream of tartar), and a moisture-absorbing agent (usually cornstarch).