A pure substance is a material that has a constant composition and has consistent properties throughout the sample. Based on the substances you listed, the following can be classified as pure substances:
- Silver (Ag) - This is a pure element, so it is a pure substance.
- Baking Soda (NaHCO3) - This is a chemical compound with a defined formula and composition, making it a pure substance.
The other two options:
- Smoothie - This is a mixture of various ingredients and cannot be classified as a pure substance.
- Flour - This is also a mixture (e.g., wheat flour may contain various components, depending on processing), so it is not a pure substance.
In summary, the pure substances among your options are Silver (Ag) and Baking Soda (NaHCO3).