1-6 Classification of Matter (Sections 3.3 and 3.4, p )

Element: any item from the Periodic Table of the Elements. Elements cannot be broken down into other substances by chemical means. Elements are composed of atoms. Examples: Cu, Al. Elements are pure substances.

Compound: two or more elements chemically combined (bonded) in the same proportions. Example: water has the elements H and O in a ratio of 2 to 1 respectively. Other examples include NaCl, CuSO 4. Compounds are pure substances. Just like elements are made of atoms, compounds are composed of molecules.

Mixture: two or more substances physically combined. Examples: salt water, iron and sand. The substances may be separated by a physical process like evaporation, magnetism, etc. Mixtures are not pure

Homogeneous Mixtures have the same properties throughout. Ex: air, salt water. Think of making a smoothie in a blender (after mixing) Heterogenous Mixtures have different regions with different properties: dirt, pizza. Not blended smoothie - stratified layers

1-7 Changes in Matter (Sections 3.2 and 3.5, p , 64-65) Physical Change: do not affect the composition of a substance. Phase changes, like ice melting, are physical changes. Separation of mixtures involve physical changes. Dissolving is also a physical change.

Chemical Change: do affect the composition of a substance, resulting in a change to the compound. Chemical changes typically involve energy (heat, light, electricity) and can often be recognized by a color change, production of gas, or formation of precipitate. Example: Separation of H 2 O into H 2 and O 2 using the process of electrolysis in PIB

Nuclear Change: affects the composition of the atom’s nucleus, thereby changing the element.

Practice: State whether the process is chemical or physical. Alcohol ignites when a flame is brought near it: Chemical Alcohol feels cool when spilled on the skin: Physical A glass of water evaporates overnight: Physical Baking powder causes biscuits to rise: Chemical