Changes in Matter Matter Lecture 2

Physical Change No new substance is formed Examples: Change of color (with no change in composition) Grinding of substances into powders

Change of phase/state (solid, liquid, gas) Dependent on temperature and pressure

Phase Changes

Chemical Change Process that involves one or more substances forming something new Always produces a change in properties Examples: Rusting of iron Souring of milk Burning of paper

Chemical Reaction Chemical changes are chemical reactions Reactants  products

Law of Conservation of Mass Matter cannot be created or destroyed True for all chemical and physical changes Massreactants = Massproducts Example: If 11.2 g of hydrogen and 88.8 g of oxygen react to form water, how much water will be formed?

Both chemical and physical changes involve changes in energy… Endothermic Absorbs energy Examples: Melting ice Water absorbs energy to break down into oxygen and hydrogen gas Exothermic Releases energy Burning paper Freezing water