What are two examples of chemical changes that occur in the world around us? Why are they chemical changes?

Answer 1

Chemical changes involve the transformation of substances into new substances with different chemical properties. Here are two examples:

1. Rusting of Iron: When iron is exposed to oxygen and moisture over time, it undergoes a chemical reaction that produces iron oxide, commonly known as rust. This process not only changes the composition of the iron but also alters its physical properties, making it weaker and more brittle. The formation of rust is a clear example of a chemical change because new substances (iron oxide) are formed.

2. Combustion of Wood: When wood burns, it reacts with oxygen in a chemical reaction known as combustion. This process produces heat, light, carbon dioxide, water vapor, and ash. The wood is transformed into ash and gases, which are distinctly different from the original material. This is a chemical change because new products are formed, and the original wood cannot be recovered in its original form.

In both examples, the original substances undergo a fundamental change at the molecular level, resulting in new substances with different properties, thus qualifying as chemical changes.

Answer 2

again please

Answer 3

Sure! Here are two examples of chemical changes that occur in the world around us, along with explanations of why they are considered chemical changes:

1. Fermentation of Sugar: In the fermentation process, yeast converts sugars into alcohol and carbon dioxide. For example, when glucose (a type of sugar) is fermented, the yeast consumes the sugar and produces ethanol (alcohol) and carbon dioxide as byproducts. This is a chemical change because the original sugar molecules are transformed into entirely new substances (ethanol and carbon dioxide) with different chemical properties and structures.

2. Baking a Cake: When a cake is baked, various ingredients like flour, sugar, eggs, and baking powder undergo chemical reactions due to the heat of the oven. For instance, the baking powder releases carbon dioxide gas, which causes the cake to rise, and proteins in the eggs undergo denaturation and coagulation, giving the cake its structure. The final product (the baked cake) has a different composition and properties compared to the raw ingredients, making this a chemical change.

In both cases, the original substances change into new substances with distinct characteristics, signifying that a chemical change has occurred.