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Section 2.1: Classifying Matter
Scientists like to classify things. One way that scientists classify matter is by
its composition. Ultimately, all matter can be classified as
mixtures, elements and compounds.
Section 2.1: Classifying Matter
Pure Substances What is Matter? Anything that has mass and
takes up space (volume) Based on matter’s composition, it can be
divided into Pure Substances and Mixtures.
Matter Flowchart
MATTER
Can it be separated by physical means?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes no
Can it be decomposed by chemical means?
noyesIs the composition uniform?
noyes
Section 2.1: Classifying Matter
Pure Substances Def.-matter that always has exactly the same
composition (ex. Table salt, table sugar) Key Concept: Every sample of a given substance
has the same properties because a substance has a fixed, uniform composition.
2 Categories of substances: elements and compounds
Section 2.1: Classifying Matter
Elements Def.-a substance that cannot be broken
down into simpler substances Key Concept: An element has a fixed
composition because it contains only one type of atom.
Section 2.1: Classifying Matter
Elements: Examples of Elements Carbon (C), Aluminum (Al)- solid at RT Oxygen (O), Nitrogen (N)- gases at RT Bromine (Br), Mercury (Hg)- liquid at RT
Section 2.1: Classifying Matter Elements: Symbols for Elements
Developed in 1813 by Swedish chemist Jons Berzelius
Symbols contain 1 or 2 letters Symbols based on Latin names of the
elements Gold is Au Aluminum is Al
Section 2.1: Classifying Matter
Compounds Def.-a substance that is made from two or
more simpler substances and can be broken down into those simpler substances (elements or other compounds)
H2O→2H + O
Section 2.1: Classifying Matter
Compounds Properties of a compound differ from the
properties of the substances from which it is made.
Ex. H and O are gases at room temp.; H2O is liquid at room temp.
Section 2.1: Classifying Matter
Compounds Key Concept: A compound always
contains two or more elements joined in a fixed proportion.
Ex. SiO2- 2 (O) atoms for every 1 (Si) atom
Ex. H2O-2 (H) atoms for every 1 (O) atom
Section 2.1: Classifying Matter
Mixtures 2 types: heterogeneous and homogeneous Retain some of the properties of their
individual substances Properties of a mixture are less constant
(vary) than the properties of a substance.
Section 2.1: Classifying Matter
Mixtures Key Concept: The properties of a mixture
can vary because the composition of a mixture is not fixed.
**Mixtures can be classified by how well the parts of the mixture are distributed throughout the mixture.
Section 2.1 Classifying Matter Mixtures: Heterogeneous and
Homogeneous Mixtures Heterogeneous- the parts of the mixture are
noticeably different from one another Ex. Sand Homogeneous-the substances are so evenly
distributed that it is difficult to distinguish one substance in the mixture from another
Ex. Water, steel
Section 2.1 Classifying Matter
Is the mixture uniform throughout? If the answer is NO, the matter is a
heterogeneous mixture. Considered the “least mixed.” Does not appear to be the same throughout. Particles are large enough to be seen and to be
separated from the mixture.
Section 2.1 Classifying Matter
Is the mixture uniform throughout? If the answer is YES, the matter is a
Homogenous mixture.
Matter Flowchart
MATTER
Can it be separated by physical means?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes no
Can it be decomposed by chemical means?
noyesIs the composition uniform?
noyes
Section 2.1 Classifying Matter
Solutions, Suspensions, and Colloids The size of the particles in a mixture has an
effect on the properties of the mixture. Key Concept: Based on the size of its
largest particles, a mixture can be classified as a solution, a suspension, or a colloid.
Section 2.1 Classifying Matter
Solutions Def.-the mixture that forms when substances
dissolve and form a homogeneous mixture Ex. Sugar water, salt water,
lemonade
Section 2.1 Classifying Matter
Solutions *They do not separate into distinct layers
over time. *They cannot be filtered. *Light passes through them. The particles in a solution are too small to
settle out of the solution, be trapped by a filter, or scatter light.
Section 2.1 Classifying Matter
Suspensions Def.-a heterogeneous
mixture that separates into layers over time
Ex. Amoxicillin, Muddy water, Flour suspended in water
Section 2.1 Classifying Matter
Suspensions *Suspended particles settle out of a mixture
or are trapped by a filter They scatter light in all directions because
the particles are large; suspensions are cloudy.
Section 2.1: Classifying Matter
Colloids Def.-a mixture that contains some particles
that are intermediate in size between the small particles in solution and larger particles in a suspension
Ex. Milk, fog
Section 2.1 Classifying Matter
Colloids Do not separate into layers Cannot be filtered Since they also contain larger particles, they
scatter light