Why is a stick of chalk pure substance but candy not?

* Composition: Chalk is primarily composed of calcium carbonate (CaCO3), a naturally occurring mineral. Calcium carbonate is a chemical compound made up of calcium, carbon, and oxygen atoms in a fixed proportion.

* Uniformity: Chalk is a uniform substance throughout. Every part of a chalk stick has the same chemical composition and properties, making it a homogeneous mixture.

* Definite properties: Chalk exhibits definite physical and chemical properties, such as a white or grayish color, a soft texture, and a tendency to produce a powdery residue when rubbed against a surface. Its chemical behavior, like reacting with acids to release carbon dioxide gas, is also consistent.

Candy

* Composition: Candy is a broad term that encompasses a wide variety of sweet treats, each with its unique recipe. Different types of candy may contain various ingredients such as sugar, corn syrup, chocolate, nuts, fruits, flavors, and colors.

* Variability: Candies can differ significantly in their composition and properties. For example, some candies are primarily made of sugar and syrup, while others contain a high proportion of nuts or fruits. The color, texture, and flavor of candies can vary greatly depending on the specific ingredients used.

* Indefinite properties: Candies do not have a definite composition or set of properties. The properties of a particular candy depend on the specific ingredients and proportions used in its preparation, which can vary between different batches and brands.

Therefore, a stick of chalk is considered a pure substance because it has a uniform composition and definite properties throughout, whereas candy is not a pure substance due to its variable composition and indefinite properties.