Question

being hungry after a long day at calvert hall a student arrives home and mixes all the dry ingredients for making a loaf of bread into a bowl. once the dough is made he forms the dough and puts it into a bread pan. he places the dough into the oven and cooks it for the designated time at 350°f. the student removes a loaf of bread hot from the oven. he then cuts a slice off the loaf and butters it. he decides to toast another piece of bread, but leave it in the toaster too long. the bread comes out black and the kitchen if full of smoke. you didnt dry the bread knife you used when you washed it and reddish - brown spots appeared on it. you also left the butter on the counter, and it starts to melt due to the temperature in the house. he eats the first piece of bread that he butters which digests in his stomach. in throwing away the burned piece of toast he crushes it in his hands as it falls into the trash bin. scenario: list two indicators that a chemical change occurred. complete the table below filling in whether this is an example of a physical or chemical change and give evidence for your choice. physical or chemical change? evidence

Explanation:

1. Bread - Chemical Change: When bread is cooked in the oven at 350°C, new substances are formed due to the heat - induced chemical reactions in the dough. For example, the Maillard reaction causes browning and flavor development, which are chemical changes. Also, when bread burns and turns black, it is a chemical change as the carbon - based compounds in the bread react with oxygen in the air to form new substances like carbon dioxide and carbon (ash).
2. Digestion - Chemical Change: In the stomach, the bread is broken down by acids and enzymes. These chemical agents break the complex carbohydrates, proteins, and fats in the bread into smaller molecules that can be absorbed by the body. This is a chemical change as the chemical structure of the bread components is altered.

Answer:

1. Chemical Change; Evidence: Browning and flavor development during baking (Maillard reaction), burning and turning black.
2. Chemical Change; Evidence: Breakdown by stomach acids and enzymes.