Physical Science Ms. Pollock 2008-2009 Composition of Matter Physical Science Ms. Pollock 2008-2009

Pure Substances Every material has its own properties. Properties can be used to identify a material. Pure substance – type of matter with fixed composition Element or compound Helium, aluminum, water, salt

Elements All atoms in substance with same identity About 92 naturally occurring Over 20 lab-created Organized in periodic table

Compounds Substance in which two or more atoms are combined in a fixed proportion Cannot be separated by physical means – must be chemical Look different from component elements

Mixtures Material made of two or more substances that can easily be separated by physical means Homogeneous – different materials not easily distinguished Heterogeneous – different materials easily distinguished

Heterogeneous Mixtures Different materials easily identified Granite, concrete, dry soup mix Most everyday substances

Homogeneous Mixtures Two or more gaseous, liquid, or solid substances blended evenly throughout Vinegar, soft drink (without visible ice)

Colloids Type of mixture with particles that are larger than those in solutions but not heavy enough to settle out Gelatin, paint, water Distinguished by Tyndall effect – light scattered by colloids

Suspensions Heterogeneous mixture containing a liquid in which visible particles settle Muddy pond water, river delta