Chapter 1. Money
Unit 1. The History of Money
Unit 2. Smart Vending Machine
Unit 3. Andy Warhol: Art and Money
Unit 4. How Can I Pay?
Chapter 2. Salt
Unit 1. Salt, the White Gold
Unit 2. Does the Sea Freeze?
Unit 3. Huge Artwork Made of Salt
Unit 4. Which Seawater Is Saltier?
Chapter 3. Environment
Unit 1. Cars for the Environment
Unit 2. Plastic Island
Unit 3. Green Buildings in Cities
Unit 4. Special Farming with Ducks
