Chapter 2 Notes II CHEMICAL AND PHYSICAL CHANGES

PROPERTIES OF MATTER What is matter? What is mass? Anything that has mass and takes up space The amount of matter an object contains

SUBSTANCES A substance is matter that has a definite and uniform composition One type of “stuff”

MIXTURES A mixture is a physical blend of two or more substances. They can be physically separated. How? One type of “stuff” More than one type of “stuff” together

HETEROGENEOUS vs. HOMOGENEOUS There are two different types of mixtures. A heterogeneous mixture is one that has more than one phase (part of uniform composition) A homogeneous mixture has only one phase.

MIXTURES Not uniform Uniform throughout physically separable

HETEROGENEOUS OR HOMOGENEOUS? Saltwater Spaghetti sauce Muddy water Cough syrup Salad Brass

TYPES OF SUBSTANCES There are two different types of substances: AND

ELEMENTS An element is the simplest forms of matter. Each element is represented by a chemical symbol.

COMPOUNDS A compound is a substance that can be separated into simpler substances only by chemical means

TYPES OF MATTER physically separable chemically separable

PHYSICAL PROPERTIES color odor Density and hardness Melting point Boiling point solubility A quality or condition of a substance that can be observed or measured without changing the substance’s composition What are some examples?

STATES OF MATTER Matter’s state is a physical property Definite shape, definite volume solid No definite shape, definite volume liquid No definite shape, no definite volume gas

SIDENOTE: A gaseous substance that is found as a solid or liquid at room temperature is called vapor.

PHYSICAL CHANGES A physical change is one that does not involve altering the chemical composition.

CHEMICAL REACTIONS The ability of a substance to react and form new substances is called a chemical property. In a chemical reaction, one or more substances change into new substances. A reaction starts with the reactants, and the substances formed are called products.

4 CLUES TO CHEMICAL REACTION Color change Gas formed Heat/light produced/ absorbed Solid from a liquid

CHEMICAL OR PHYSICAL CHANGE? Baking cookies Boiling water Dissolving salt Burning firewood Milk spoiling Metal rusting Tearing paper Melting ice

LAW OF CONSERVATION OF MASS During any chemical reaction, the quantity of matter is unchanged. The mass of the products always equals the mass of the reactants.