Transcript Prentice Hall Physical Science Chapter 2 Notes.doc

Prentice Hall Physical Science
Chapter 2 Properties of Matter
2.1 Classifying Matter
Composition is what the material is made
of
Composition determines if a material is a
pure substance or a mixture
A. Pure Substances
• Matter that is exactly the same throughout is a pure substance; it has
the same composition throughout
1. Elements
• - a substance that cannot be broken down into simpler substances
• it contains only one type of atom; all of the atoms in a sample of an element
are exactly the same
• at room temperature, most elements are solids
• each element name is represented by a symbol
• - each symbol is one or two letters and the first letter is always capitalized
• - ex: sodium is Na
•
carbon is C
•
gold is Au
• 2.
Compounds
• a substance made of two or more simpler substances (elements or other,
simpler compounds) that be broken down into those substances with a chemical
reaction
• the properties of the compounds are different than the properties of the
elements that make them up
B. Mixtures
• Mixtures are combinations of two or more substances where each
substance maintains its own properties
The properties vary
The composition varies because the
substances can be mixed in any
proportion
Mixtures CAN be separated into their part
without a chemical reaction
• 1.
heterogeneous mixtures – the parts of the mixture are noticeably different
from one another (ex: beach sand, chili, vegetable soup)
• 2.
homogeneous mixtures – the parts of the mixture cannot be distinguished
from one another (ex: alloys, ocean water, cake batter)
• 3.
solutions – substances that dissolve to form a homogeneous mixture (ex:
salt water, kool-aid)
• liquid solutions do not separate and cannot be filtered
• light passes straight through them without being scattered
• the particles in them are too small to settle or be trapped
• 4.
suspensions – a heterogeneous mixture that separates into layers over
time (ex: muddy water, Italian salad dressing)
• a filter can separate the parts
• the particles are too larger to dissolve or be trapped
• 5.
colloids – contains particles that are intermediate in size caught between
smaller particles (homogenized milk)
• the particles do not settle out
Prentice Hall Physical Science
Chapter 2 Properties of Matter
2.2 Physical Properties
A physical property is one that can be
observed or measured without changing
the composition of the material
A. Examples of Physical Properties
• Viscosity – the tendency of a liquid to keep from flowing (resistance to
flow)
• the greater the viscosity, the slower the liquid flows
ex: honey has a very high viscosity, water
has a low viscosity
viscosity decreases as a liquid is heated
• Conductivity – a material’s ability to allow heat to flow through it
• materials with a high conductivity are called conductors and will get hot when
heated (ex:metals)
a material that is a good conductor of
heat is usually a good conductor of
electricity
• 3. Malleability – the ability of a solid to be hammered with out shattering (ex: metals)
• 4. Hardness
• 5. Melting and Boiling point
• • • -
melting point is the temperature at which a solid changes to a liquid
boiling point is the temperature at which a liquid changes to a gas by boiling
each substance has its own unique melting and boiling point (fig. 12, p. 47)
6. Density – mass/volume
• can be used to test the purity of a substance because each substance has
its own unique density
• B.
Using Physical Properties - physical properties are used to
identify a material, choose a material for a specific purpose, or to
separate the substance in a mixture
• - Using Properties to Identify Materials
• - perform tests on an unknown sample and compare the result with data for known
materials to see if they match
-
Using properties to choose materials
• - if you know what you want a material to do, you can choose materials that have
those properties
C. Using Properties to Separate
Mixtures
-
Filtration
- uses the sizes of particles to separate
them
- large particles are caught in the filter
paper, strainer, etc.
-
Distillation
- separates substances based on their
boiling points
• - ex: a mixture of alcohol and water can be separated by boiling the mixture. Since
alcohol and water have different boiling points, the one with the lower boiling point will
boil first. Its gas can be collected, cooled until it becomes liquid again.
D. Recognizing Physical Changes
• a physical change is one in which some of the properties of a material may
change, but the substances stay the same; the chemical composition stays the
same
• a lot of physical changes can be reversed
• ex: freezing water, sawing a log, crashing a car, cutting hair
Prentice Hall Physical Science
Chapter 2 Properties of Matter
2.3 Chemical Properties
a chemical property is the ability to cause
a change in the composition of matter; it
is how one substance interacts with
another
chemical properties can only be observed
when a substance is changing into a
different substance
A. Observing Chemical Properties
- Flammability – the ability to burn in
the presence of oxygen
• - Reactivity – how readily a substance combines chemically with
another substance
- ex: oxygen is highly reactive, nitrogen
is not very reactive
B. Recognizing Chemical Changes
• a chemical change occurs when a substance reacts to form one or
more new substances (ex: iron rusting, paper burning, baking soda and
vinegar giving off a gas)
changing color, producing a gas, and
forming a precipitate are all evidence tat
a chemical change has taken place
• a precipitate is a solid that forms and separates from a liquid mixture
C. Is a Change Chemical or Physical?
• Are different substance present after the change or is it still the same
material?
Ex: burning paper
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Cutting down a tree
Coloring hair
Painting a house
Sugar dissolving in water