8/29/2011 Objectives: Distinguish that homogenous mixtures are solutions and heterogeneous mixtures are colloids or suspensions. Interpret and create models (words or pictures) that represent atoms, molecules, elements, compounds, and mixtures at the particle level. Catalyst: Convert the following: km to nm cL to L

Drawing Atoms Atoms are the smallest unit of matter They are too small to see except with the most powerful microscopes, so we draw them to help us understand

What do we call these things? An Atom 3 Atoms

Drawing molecules Molecules are groups of atoms that are joined together These atoms can be of the same or different elements

Substances All molecules are the same – Element: all atoms are the same – Compound: there are different atoms within the molecule, but each molecule is the same

This molecule is 2 atoms joined together but we don’t call it “2 atoms joined together” we say it is one molecule This molecules is 4 atoms of two different types joined together to make a compound element compound

Pure substances include: Elements are found on the periodic table – Some elements are: iron, gold, silver, aluminum, and carbon Compounds are bonded groups of atoms – some basic compounds are: Carbon monoxide (CO), and carbon dioxide (CO 2 ), water (H 2 O), hydrogen peroxide (H 2 O 2 ).

Mixtures Molecules are not all the same

Element vs.Compounds vs. mixtures Element CompoundMixture Single atom two different two or more Or group of atoms joined molecule types Same atoms *heterogenous (looks different throughout) (looks different throughout) *homogenous (looks the same throughout) *homogenous (looks the same throughout)

Many things we experience are mixtures of elements and compounds: Heterogenous: Coke (bubbles) Milk (globs of fat) Chocolate chip cookies (chocolate chips) Homogenous: Kool-Aid The air Vinegar

Homogenous v. Heterogenous Atoms/Molecules evenly spread throughout Atoms/Molecules separated or “clumped”

(Gas) atoms of one Element Atoms of the same Element (Solid)

This one likes to go round in pairs as a gas (molecules) Another element A mixture of two elements

This is not a mixture, it is a COMPOUND of two elements This is just a mixture of two elements

Definitions Matter – anything that occupies space and has mass Physical properties – properties that can be observed and measured without changing the chemical makeup of the substance Density – mass of material within a given volume Aqueous solution – a solution in which something is dissolved in water.

Definitions Mixture – combination of substances in which each substance retains its individual properties Suspension – a mixture containing large, dispersed solid particles that can settle out or be separated by filtration Colloid – a mixture containing solid particles small enough to remain suspended and not settle out Tyndall effect – the scattering of a beam of light caused by reflection from suspended particles

Definitions Solution – a homogeneous mixture of two or more substances Solvent – the thing doing the dissolving Solute – the thing getting dissolved