Chapter 17Section 1—Composition of Matter
Section 1• Pure Substances-
– Either an element or a compound that cannot be broken down into simpler components and still maintain the properties of the original substance
ex: helium, aluminum, water, salt
Elements-
a substance whose atoms are all alike*there are 90 found in nature/20 others made in labs
• Compounds– A substance in which the atoms of
two or more elements are combined in a fixed proportion• Ex: water, chalk, etc.• Compounds usually look different from
the elements in them (salt—Na and Cl)
• Mixtures-– A material made up of two or more
substances that can be easily separated by physical means
– Heterogeneous Mixtures:• A mixture in which different materials
can be distinguished easily• Ex: granite, concrete, pizza
•Homogeneous Mixtures:
• Contains two or more gaseous, liquid or solid substances blended evenly throughout
• Ex: soft drinks, vinegar, etc
• Solution-• A homogeneous mixture of
particles so small that they cannot be seen with a microscope and will never settle to the bottom of their container– Ex:
– Colloid:– A type of mixture that never settles– It’s particles are larger than those in
solutions but not heavy enough to settle
– Ex: some paints, shampoos, hairgel,
• Tyndall Effect:• The scattering of light by
colloidal particles• A light beam is invisible as it
passes through a solution, but can be seen readily as it passes through a colloid– Ex: pg. 523
• Suspensions:• A heterogeneous mixture
containing a liquid in which visible particles settle– ex: muddy pond water (visible
particles settle out eventually)
SECTION 2—Properties of Matter
• Physical Properties-• Any characteristic of a material
that can be observed without changing the identity of the substance– Ex: color, shape, size,
melting/boiling pt, etc.
Physical Properties may be used to separate substances (in a mixture)
• Physical changea change in size, shape or state of matter(might involve energy changes but element or compound itself does not change)
*PHYSICAL CHANGES ARE PHASE CHANGES!!
Distillation-process for separating substances in a mixture by evaporating a liquid and recondensing its vapor
• Chemical properties– A characteristic of a substance that
indicates whether it can undergo a certain chemical change
– Ex: flammability, exposure to light
Chemical Change:
A change of one substance to anotherEx: foaming of antacid tablets, silver
tarnishing, etc.*A NEW SUBSTANCE IS FORMED BY A CHEMICAL CHANGE!!!!
Weathering—Chemical or Physical?• Some weathering changes are
physical and some are chemical
• Physical—rocks split, streams cut through rock, etc.
• Chemical—calcium carbonate from limestone changes to calcium hydrogen carbonate– Ex: White Cliffs of Dover
The Conservation of Mass• Law of Conservation of MassMatter is neither created nor
destroyed (during a chemical change)
The mass of all substances that are present before a chemical change EQUALS the mass of all the substances that remain after the change