Download Chapter 18 - Trimble County Schools

Chapter 18
18.1 – Composition of Matter
Objectives
 Define pure substances and mixtures.
 Identify elements and compounds.
 Compare and contrast solutions, colloids,
and suspensions.
Pure Substances
 Type of matter with a fixed composition
 Can be element or compound
 Element = pure substance in which all
atoms have the same identity
 90 elements found on Earth
 20+ have been made in labs
 Most are unstable and exist for a short period of
time
Pure substance
 Compounds = when 2 or
more different elements
combine in a fixed
proportion
 Water, Table Salt (NaCl)
 Molecules = particle
consisting of 2 or more
atoms bound together
Mixtures
 Material made up of 2 or more substances
that can be easily separated by physical
means
 Heterogeneous mixtures = mixture in
which different materials can be easily
distinguished
 Granite, Concrete, Pasta Salad, Clothing
Mixtures
 Homogeneous mixture = 2 or more
substances blended evenly throughout
 Soft drinks, Pudding, Vinegar
 Solution = particles so small that they
cannot be seen with microscope and will
never settle to the bottom of their
container
Colloids
 Mixture with particles that are larger than
those in solutions but not heavy enough to
settle out
 Greek word for “glue”
 Examples: Milk, Gelatin
Detecting Colloids
 Pass light beams through
 Solutions = no light comes through
 Colloids = light readily passes through
 Tyndall Effect = scattering of light by
colloidal particles
Suspensions
 Heterogeneous mixture containing liquid in
which particles settle
 Example: Pond Water
In-Class Assignment/Homework
 18.1 Reinforcement & Enrichment WKT
 Reinforcement #10-15 use p. 553
 Enrichment – complete like examples
 Pond Water = Mixture  heterogeneous 
suspension
 Potassium fluoride = substance  compound
 Carbon = Substance  element