8/29/2011Objectives: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: 1. 0.25 km to nm2. 7.3 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 (CO2), water (H2O), hydrogen peroxide (H2O2).

Mixtures• Molecules are not all the same

Element vs.Compounds vs. mixtures

Element Compound MixtureSingle atom two different two or moreOr group of atoms joined molecule typesSame atoms *heterogenous

(looks different

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. HeterogenousAtoms/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