Two spoons are kept in a humid environment: one is made of iron and the other is made of stainless steel. Which spoon will rust and why?

Here are the answers to the questions:

2. The iron spoon will rust. Iron rusts when it reacts with oxygen and moisture in the air (a humid environment) to form iron oxide (rust), which is a chemical change. Stainless steel is an alloy that contains chromium, which forms a protective layer on its surface, making it resistant to rusting.

3. When lemon juice is added to baking soda, you will observe fizzing or effervescence (the production of bubbles). This is due to the release of carbon dioxide gas. The word equation for the reaction is:

   $$\text{Lemon juice (Citric acid) + Baking soda (Sodium bicarbonate)} \rightarrow \text{Carbon dioxide + Water + Sodium citrate}$$

4. Tearing of paper is a physical change because it only alters the size and shape of the paper. The chemical composition of the paper (cellulose) remains unchanged, and no new substances are formed. Burning of paper is a chemical change because the paper reacts with oxygen to produce entirely new substances, such as ash, carbon dioxide, and water vapor. The original paper cannot be recovered from these new substances.

5. To classify the changes as reversible or irreversible, please provide the list of changes. The list is not visible in the image.