Question

lesson 2 check:

1. how does reducing the rate of a chemical reaction affect the rate of which it occurs?
2. while hiking in the woods you see a brown rotting apple. what physical signs of the apple are evidence of a chemical reaction?
3. a clear liquid is poured into a container of another clear liquid. a cloudy yellow substance forms out of nowhere. the rest of the liquid remains clear. what happened? explain:
4. some silver coins are found inside of an ancient ship wreck. they are coated with a black crust. ask a question that can help you discover if a chemical or physical reaction occurred. explain:

Explanation:

1. Reducing the rate of a chemical reaction means it will occur more slowly. The rate of a reaction is a measure of how quickly reactants are converted to products.
2. The brown color and rotting (decomposition) are physical signs. Decomposition is a chemical reaction where complex substances break down into simpler ones. The change in color (from the original apple color) is often due to chemical changes like oxidation.
3. A chemical reaction occurred. When two clear liquids are mixed and a new substance (the cloudy yellow substance) forms, it indicates a chemical change. In a chemical reaction, new substances with different properties (like color and state - here a solid or precipitate forming from liquids) are produced.
4. One possible question: "Can the black crust be easily wiped off to reveal the original silver coin underneath?" If it can be easily wiped off (like a physical coating such as dirt), it might be a physical change. But if it requires a chemical process (like a chemical reaction to remove it, e.g., using an acid to react with the crust), then it is likely a chemical reaction (such as silver tarnishing - a chemical reaction of silver with sulfur - containing compounds in the environment to form silver sulfide which is black).

Answer:

1. It makes the chemical reaction occur more slowly.
2. The brown color and the rotting (decomposition) of the apple.
3. A chemical reaction occurred as a new substance (the cloudy yellow substance) formed from the two clear liquids.
4. "Can the black crust be easily wiped off to reveal the original silver coin underneath?" (Explanation as above).