Classification of Matter Chapter 18

Composition of Matter Section 1

Pure Substances A type of matter with a fixed composition Examples Helium Aluminum Water Salt

Elements All substances are made of atoms If all the atoms have the same identity, the substance is an element There are approximately 90 naturally occurring elements Helium, Copper, Oxygen, Gold More than 20 more are made in labs Americium, Nobellium

Compounds Compound Two or more different elements combined in a fixed proportion Water (H 2 O) Glucose (C 6 H 12 O 6 ) Carbon dioxide (CO 2 ) Compounds will have properties different than the properties of the individual elements that make it up Na+ (very reactive solid) Cl- (poisonous gas) Salt (NaCl) edible salt

Molecules A particle consisting of two or more atoms that are bonded together chemically All molecules are compounds, but not all compounds are molecules O 2 is a molecules but not a compound

Mixtures Mixture A material made up of two or more substances that can be easily separated by physical means Pizza Soda Orange Juice Dyes Do not always contain the same proportions of substances that make them up

Mixtures Heterogeneous Mixtures The materials can be distinguished easily Granite Trail Mix Dry Soup Mixes Poly-cotton Fabrics

Mixtures Homogenous mixture Contain two or more gaseous, liquid, or solids blended evenly together Vinegar Soft drinks in sealed bottles Blood Solutions are homogenous mixtures of particles so small that they cannot be seen with a microscope and won’t settle out

Mixtures Colloids Mixture containing components in varying proportions (heterogenous) Won’t settle when left standing Fog Milk Paint Colloids can be identified by passing a beam of light through them A light beam can pass through a solution, but not through a colloid

Mixture Suspensions Neither solution or colloid Particles are temporarily suspended, but will eventually settle out Pond water

Comparing Solutions, Colloids, and Suspensions DescriptionSolutionColloidsSuspension Settle upon standing?No Yes Separate using filter paper? No Yes Particle Size0.1 – 1nm1 – 1,000 nm>1,000 nm Scatter Light?NoYes