Chapter 3: Matter--Properties and Changes 3 Matter—Properties and Changes 3. LAB
Chapter 2: Properties of Matter
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Transcript of Chapter 2: Properties of Matter
Chapter 2: Properties of Matter
Matter – has mass takes up space
Can be classified as a substance or mixture
Substance vs. Mixtures
Substance Mixture A substance always has the same
composition
Every sample has the same properties
Two types are Elements and Compounds
Properties can vary because the composition in not fixed
Classified by how well the parts are distributed
Two types are heterogeneous and homogeneous
Substances
Element Compound A substance that
cannot be broken down
An atom is the smallest particle
Fixed composition because it contains only one type of atom
Made from two or more simpler substances
Can be broken down Properties are
different than those it is made of
Contains elements in a fixed proportion
Mixtures
Heterogeneous Homogeneous The parts are different Evenly distributed so
difficult to distinguis Appears to contain
only one substance
Now it is your turn… you tell me: Homogeneous or Heterogeneous
Flat soda pop Cherry vanilla ice cream Sugar (C2H3O2) Salt (NaCl) City Air Iron (Fe) Beach Sand Spaghetti Sauce
Mixtures can also be classified by their largest particle
Solutions When dissolves and forms a homogeneous mixture Cannot be filtered
Suspension A heterogeneous mixture that separate into layers
over time Settle out or filtered out Are cloudy
Colloids Particles of intermediate size Do not separate Cannot filter
Physical Properties
A physical property is any characteristic that can be observed or measured without changing the composition
Examples: Viscosity Conductivity Malleability Hardness Melting/Boiling Density
Physical Properties Viscosity
Resistance to flowing The greater the viscosity the slower the
liquid moves Usually decreases when heated
Conductivity Ability to allow heat to flow Materials with high conductivity are
conductors
Malleability
Can be hammered Most metal are malleable Solids that shatter when struck are
brittle
Hardness
One way to compare is to see which can scratch the other
Diamond is the hardest known material
Melting/Boiling
Melting: changes from a solid to a liquid
Boiling: temperature a which it boils
Density
Can be used to test the purity Ratio of mass to its volume D = Mass/Volume
Physical Properties
Are used to identify a material, to choose a material for a specific purpose, or to separate the substance
Separating Mixtures (2 Ways) Filtration – process that separates based
on the size of their particles Distillation – process the separates bases
on boiling points
Filtration vs. Distillation
Physical Changes
Occurs when some of the properties of a material change but the substance in the material remains the same.
Ex. Melting Butter, Crumpling Paper, Slicing
Some can be reversed ( melting, boiling)
Chemical Properties Is any ability to produce a change in
the composition of matter Can be observed only when the
substances are changing into different substances
2 Examples Flammability
Is a materials ability to burn in the presence of oxygen
Sometimes is not a desirable property
Reactivity – Example of Chemical Property
Describes how readily a substance combines chemically with other substance.
Recognizing Chemical Changes A chemical change occurs when a
substance reacts and forms one or more new substances.
Ex. 1. Change in Color2. Production of a gas3. Formation of a precipitate
Evidences of Chemical Change 1. Change in Color
Is a clue that a chemical change has produced at least one new substance
2. Production of a Gas Bubbles can show a chemical change (ex.
Cake)3. Formation of a Precipitate
Any solid that forms and separates from a liquid
Chemical or Physical?
Even if you observe a color change, a gas, or a precipitate you cannot be sure
Ask yourself???
Are different substances being formed???-If yes then is chemical!