The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of

1. Analyze the question The question asks which substance gives soda water and other soft drinks their refreshing, slightly sharp, "fizzy" taste.

2. Explain the concept Soft drinks are carbonated. Carbon(IV) oxide (CO₂) is dissolved in the water under pressure. When the bottle is opened, the pressure drops and some CO₂ escapes as bubbles, which is the fizz you see.

Some of the dissolved CO₂ also reacts with water to form carbonic acid:

CO₂ + H₂O ⇌ H₂CO₃

Carbonic acid is a weak acid. It gives the drink its tingly, slightly tangy and refreshing taste.

3. Evaluate the options

• A. Carbon(IV) oxide: Correct. It is the gas dissolved in the drink and it produces the fizz and the characteristic taste.
• B. Carbon(II) oxide (CO): Wrong. It is a poisonous gas and is not used in drinks.
• C. Soda: Wrong. This is not a specific substance that creates the taste. "Soda water" is just the name for carbonated water.
• D. Glucose: Wrong. It adds sweetness but not the refreshing, fizzy taste. Many soft drinks contain sugar, yet the characteristic "sparkle" comes from CO₂.

4. Answer The correct option is A. carbon(IV) oxide.

5. Exam tip Remember: Carbonated = Carbon(IV) oxide. Also keep CO and CO₂ apart. CO is the poisonous gas from incomplete combustion, while CO₂ is the one in fizzy drinks, in fire extinguishers, and the one that turns lime water milky.