"Physical and Chemical Changes"

 

Physical Changes (www.quia.com)

As the ice cube melts, its shape changes as it gains the ability to flow. However, its structure does not change. Molting is an example of a physical change. A physical change is a change in a sample of matter in which some of the properties of the matter change, but the identity of the matter remains unchanged. Physiological changes can be further classified as irreversible or irreversible. A melted ice cube can refreeze, so melting is a reversible physical change. Physiological changes that involve a change of state are all reversible. Other changes of the state include evaporation, freezing (liquid to solid), and condensation (www.quia.com). Dissolution is also a reversible physical change. When a salt dissolves in water, the salt is said to have entered the liquid state. The salt can be recovered by boiling the water, leaving the salt behind.

Chemical changes

An element's chemical properties describe its ability to undergo specific chemical changes. One of the chemical properties of iron is its ability to combine with oxygen to form iron oxide, the chemical name for rust. A chemical change is also called a chemical reaction. When one substance changes into another, it's called a chemical reaction. There's a silver-gray element called zinc (Zn) that can be ground into powder.

Zinc Sulfur → Zinc (Sulfide)

ZnS→ZnS

The substances to the left of the arrow in a chemical equation are called reactants. A reactant is a substance that is present at the beginning of a chemical reaction (such as zinc and sulfur). The substance to the right of the arrow is called a product, and a product is a substance that is present at the end of a chemical reaction. A color change occurs during the reaction. The color change occurs after the reaction. These are called chemical changes.