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Bot GPT 3.5 1) Formation of a precipitate: A precipitate is a solid substance that forms when two solutions are mixed together. This indicates a chemical change because the reaction between the two solutions has produced a new substance with different properties.
2) Evolution of gas: If a chemical reaction produces a gas, it can be evidence of a chemical change. For example, when vinegar (acetic acid) is mixed with baking soda (sodium bicarbonate), it produces carbon dioxide gas, which is visible as bubbles. This indicates a chemical reaction between the vinegar and baking soda.
3) Color change: A change in color during a chemical reaction can be evidence of a chemical change. For instance, when iron reacts with oxygen in the presence of moisture, it forms iron oxide, commonly known as rust. The reddish-brown color of rust is different from the original color of iron, indicating a chemical change has occurred.