Processes are classified as reversible or irreversible based on whether they increase or keep constant the total entropy of the system. Processes that cause an increase in the net entropy of the system are irreversible, ... More »

A reversible change is a physical change that can be undone. A final substance can be converted back to the original substance without creating any new material. Freezing, melting, dissolving, boiling, evaporating and co... More »

A chemical change is a process where two substances combine to form one or more new substances. This process is referred to as a chemical reaction, and it is not reversible. More »

A phase change in science refers to any substance that changes from one state to another, with possible states being gas, liquid and solid. Substances typically phase change to the closest related state, such as liquid t... More »

A few science fair project ideas using bananas include measuring which food grows mold fastest, measuring how sugar content changes in ripening bananas, and determining how air affects the ripening of bananas. Each proje... More »

A pure substance is any single type of material that has not been contaminated by another substance. Water is considered a pure substance if the water contains only hydrogen and oxygen. More »

A solvent is the prominent component of a homogenous mixture or solution made of two combined materials. A solution is made when a lesser amount of material called a solute is dissolved into the solvent. More »