Notes

. A physical change is one that affects only the physical properties of a substance, while a chemical change alters a substance at the molecular level.Properties that describe the look or feel of a substance are called physical properties Physical properties can be categorized as either intensive or extensive Extensive physical properties depend on the amount of matter present in a sample of matter. This includes the properties mass, length, and volume. The physical properties of a substance can change when conditions change, but that does not mean a different substance is created. For example, an increase in temperature can cause solid water, or ice, to melt, or liquid water to evaporate. A chemical property characterizes the ability of a substance to react with other substances or to transform from one substance to another. In a chemical change, also known as a chemical reaction, new substances are produced that usually have properties very different from those of the original substances. law of conservation of mass. This law states that matter is neither created nor destroyed during an ordinary chemical reaction. In other words, all of the atoms that were present at the beginning of a reaction are present at the end of the reaction—they have just been rearranged to bond differently and form new substances.Reactants → ProductsIn a double replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds