Activity 3.10 Describe evidences that show chemical reaction has occurred in the following chemical process: a. Rusting of iron b. Fermentation c. Souring of milk d. Growth e. Buming of paper

Sure! Here are the evidences that show a chemical reaction has occurred in each of the given processes: --- **a. Rusting of iron** **Evidence of a chemical reaction:** - **Color change:** Iron turns from metallic gray to reddish-brown (iron oxide). - **Formation of a new substance:** Rust is a new compound (iron oxide), which is different from the original iron. - **Mass change:** The mass of the iron object increases due to the absorption of oxygen and water. - **Change in texture:** The surface of the iron becomes rough and porous. --- **b. Fermentation** **Evidence of a chemical reaction:** - **Gas production:** Bubbles are released, indicating the production of carbon dioxide. - **Change in taste and smell:** The substance becomes sour or alcoholic, indicating a chemical change. - **Formation of new substances:** Alcohol and carbon dioxide are produced, which are different from the original ingredients (e.g., sugar and yeast). - **Change in volume:** The volume of the substance may increase due to gas production. --- **c. Souring of milk** **Evidence of a chemical reaction:** - **Change in taste and smell:** The milk becomes sour, indicating the production of lactic acid. - **Formation of new substances:** Lactic acid is produced, which is a new compound. - **Change in texture:** The milk may curdle or thicken. - **pH change:** The pH of the milk decreases as lactic acid is formed. --- **d. Growth** **Evidence of a chemical reaction:** - **Increase in mass:** The organism gains mass through the absorption of nutrients. - **Formation of new substances:** New tissues and cells are formed, which are chemically different from the original material. - **Change in structure:** The organism changes in size, shape, and complexity. - **Energy release:** Growth involves metabolic processes that release energy through chemical reactions. --- **e. Burning of paper** **Evidence of a chemical reaction:** - **Change in color:** The paper changes from white to black (charred). - **Formation of new substances:** Ash and gases (such as carbon dioxide and water vapor) are produced. - **Release of heat and light:** The paper burns with a flame, indicating an exothermic reaction. - **Change in mass:** The mass of the paper decreases due to the release of gases. --- These evidences indicate that a chemical reaction has occurred, as new substances are formed, and the properties of the original substances change.