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