Which of the following is not an example of a physical change?
is this the right Answer
accidentally leaving a piece of toast in the toaster until it is completely black
I would agree that burnt toast is an example of a chemical change.
I suppose if one wanted to get picky, "leaving" the toast somewhere is a physical change but burning it is a chemical change.
No, accidentally leaving a piece of toast in the toaster until it is completely black is not an example of a physical change. The correct answer is a chemical change. To understand why, let me explain the difference between physical and chemical changes.
A physical change is a change in the physical properties of a substance, such as its shape, size, or state of matter, without altering its chemical composition. In other words, the substance remains the same at a molecular level. Examples of physical changes include melting ice into water or cutting a piece of paper into smaller pieces. These changes can usually be reversed.
On the other hand, a chemical change is a process in which a substance undergoes a chemical reaction, resulting in the formation of new substances with different chemical compositions. In a chemical change, the bonds between atoms are broken and new bonds are formed. Examples of chemical changes include the rusting of iron, burning wood, or cooking an egg. These changes are usually irreversible.
In the case of accidentally leaving a piece of toast in the toaster until it turns completely black, a chemical change occurs. The heat from the toaster causes the bread to undergo a chemical reaction called "pyrolysis." This process results in the formation of carbon, which turns the toast black. Therefore, this scenario represents a chemical change rather than a physical change.