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Classification of Matter
Four classes of matter
The four classes of matter are elements, compounds, mixtures, and solutions
Homogeneous matter Appears to look similar throughout
Ex: salt, sugar, whipped cream
all parts are alike (appearance)
Question
What does the prefix “homo” mean?
Name the four classes of matter.
What are the four phases of matter?
Question
Milk in most stores is homogenized. What do you think this means?
Heterogeneous matter
Matter that has different properties
Ex: soil, cereal with raisins, concrete
Question
How is homogeneous matter different from heterogeneous matter?
Question video Why is it better to classify matter according to make-up rather than phase? Think!
What is a mixture? A combination of substances
Two or more substances that are not chemically combined
Properties of mixtures The substances in a mixture keep their separate identities (properties)
Ex: salt/pepper, sugar/water
Separating mixtures The substances in a mixture can be separated by simple physical means
Evaporation and filtration are used to separate mixtures
Types of mixtures (video) Heterogeneous mixtures are the “least mixed” of all mixtures
The different particles in mixtures are large enough to be seen
Homogeneous mixtures
Homogenous mixtures are “well mixed”
Particles are small and not easily recognized
Question
What are two ways mixtures can be separated?
Solutions (video)
A solution is a mixture in which a substance is dissolved in another, “best mixed”
Properties of a solution Particles are not large enough to be seen
Evenly spread particles Particles cannot be separated by simple physical means
Alloys (video)
Solutions of metals are alloys
Ex: gold jewelry, brass, sterling silver, stainless steel
Questions
Describe an alloy. What are two properties of a solution?
Pure substances (video) Homogeneous matter is also known as a pure substance
Properties: one kind of material with the same properties
Elements Simplest types pure substances
Made of only one type of atom
Cannot be broken down by chemical processes or heating
What is an atom? (video)
The smallest particle of an element that has the same properties of the element is the atom
Chemical symbols A short way of representing elements
Consists of one or two letters
An abbreviation for an element
Question
What are two properties of elements?
What is an atom?
Compounds (video) Pure substances made of more than one element is a compound
Ex: carbon dioxide, ammonia, sugar
Molecules Two or more atoms that are
chemically bonded Smallest part of a
compound that has the same properties of that compound
Separating compounds Compounds are made of molecules
Compounds can be broken down into simpler substances by heating and electricity
Questions
How is a molecule different from an atom?
How is a compound different from an element?
Chemical formulas
Combinations of chemical symbols are chemical formulas (C3H7OH) (NH3)
Subscript A subscript is placed to the lower right of the chemical symbol
It gives the number of atoms of the element
Questions
How is chemical symbol different from a chemical formula?
Chemical equations A description of a chemical reaction using symbols and formulas is a chemical equation
Coefficient The number used to balance a chemical equation (coefficient)
“Balanced” means the same number of reactants and products
Questions
How is a subscript different from a coefficient?
Chemical reactions
Reactants are the substances that enter a chemical reaction
Products are the substances formed by a chemical reaction
Chemical equations 2H2+O2 (reactants) 2H2O The arrow means yields
(makes) C + O2 CO2 (products)
Reactants (yield) products
Questions
What does the arrow mean in a chemical equation?
What is a chemical equation?
Questions
What is another name for a chemical reaction?
On what side of a chemical reaction would you find the reactants?
Products?