Question

part b read each scenario. decide whether a physical or chemical change has occurred and give evidence for your decision. the first one has been done for you to use as an example. scenario 1. umm! a student removes a loaf of bread hot from the oven. the student cuts a slice off the loaf and spreads butter on it. physical or chemical change? physical evidence... 2. your friend decides to toast a piece of bread, but leaves it in the toaster too long. the bread is black and the kitchen is full of smoke. chemical change? chemical evidence... 3. you forgot to dry the bread knife when you washed it and reddish brown spots appeared on it.

Explanation:

1. Physical Change: Cutting a slice of bread and spreading butter are physical changes. The bread's shape changes, but its chemical composition remains the same. There is no new substance formed.
2. Chemical Change: Leaving bread in the toaster too long causes it to burn. Burning is a chemical - change process. The bread turns black, smoke is produced, and new substances are formed due to the high - temperature reaction with oxygen in the air.
3. Chemical Change: Forgetting to dry a bread knife after washing it leads to rusting (the reddish - brown spots). Rusting is a chemical change where iron in the knife reacts with oxygen and water to form iron oxide.

Answer:

1. Physical Change; Evidence: Change in shape, no new substance formed.
2. Chemical Change; Evidence: Black color, smoke, new substances formed.
3. Chemical Change; Evidence: Reddish - brown rust spots, new substance (iron oxide) formed.