Introduction
In this experiment, we place iron nails in four different test tubes containing water, oil, vinegar, and lemon juice. This allows us to observe the effects of different substances on iron nails, leading to physical and chemical changes.

Test Tube 1: Iron Nails in Water
- **Physical Change**: No immediate visible change occurs when iron nails are placed in water.
- **Chemical Reaction**: Over time, rusting will occur due to the reaction between iron, oxygen from the air, and water. This is a chemical change, producing iron oxide (rust).

Test Tube 2: Iron Nails in Oil
- **Physical Change**: The nails will remain unaffected in oil.
- **Chemical Reaction**: No rusting occurs because oil acts as a barrier, preventing moisture and oxygen from reaching the iron, thus inhibiting any chemical change.

Test Tube 3: Iron Nails in Vinegar
- **Physical Change**: The vinegar may cause the iron to appear dull.
- **Chemical Reaction**: Vinegar (acetic acid) reacts with iron, leading to the formation of iron acetate and hydrogen gas. This is a significant chemical change, resulting in the corrosion of the nails.

Test Tube 4: Iron Nails in Lemon Juice
- **Physical Change**: Similar to vinegar, the lemon juice may dull the iron's surface.
- **Chemical Reaction**: The citric acid in lemon juice reacts with the iron, causing corrosion and producing iron citrate and hydrogen gas. This chemical change also leads to the deterioration of the nails.

Conclusion
This experiment illustrates the varied effects of substances on iron nails. Water and acidic solutions (vinegar and lemon juice) lead to chemical changes and rusting, while oil acts as a protective layer, preventing any reactions. Understanding these changes is crucial in fields like chemistry and material science.