Monday, December 26, 2011

Classification of Matter - Chemistry HW 4/19/11

According to the Distribution of their properties and composition throughout the material
1.       Homogeneous
A homogeneous material has uniform properties and composition throughout and therefore has only one phase
2.       Heterogeneous
A heterogeneous material does not have uniform properties and composition throughout.
According to composition
1.       Pure Substance – A pure substance is a material made up of only one substance. Every pure substance has a unique set of chemical and physical properties. Pure substances can be further classified into:
a.       Elements – Elements are substances that cannot be separated into simpler substances by a chemical change. It is a pure substance whose atoms all have the same atomic number. Elements may be classified as:
·         Metals – Metals have high thermal conductivity. They have mobile particles that can carry thermal or heat energy from one point of the material to another. They also have high electrical conductivity. Metals have charge carriers that are free to move and carry electrical charges from one point of the material to another.
·         Non-metals – Nonmetals usually do not conduct heat and electricity very well. They have little luster and seldom reflect light. Nonmetals are usually brittle. They are neither malleable nor ductile. Nonmetals may be solid (such as carbon and sulfur), liquid (bromine) or gas (oxygen and nitrogen) at room temperature.
·         Metalloids – Metalloids are elements that have properties intermediate between metals and nonmetals. Because of their properties, metalloids like silicon and germanium are used in electronic industry as semiconductors.
b.      Compounds – Compounds are substances that contain two or more elements combined in a fixed proportion. This gives rise to a substance with properties which are different from those of the combining elements.
·         Organic Compounds – compounds found in living organisms
·         Inorganic Compounds – compounds found in inanimate or nonliving components of our world
o        Acid – causes litmus paper to turn red
-          Tastes sour
-          Dissolves metals, producing various salts
o        Base – causes litmus paper to turn blue
-          Tastes bitter
-          Feels slippery on the skin
-          Reacts with acids to form salts and water
o        Salts – This substance is neutral, meaning, it is neither an acid nor a base.
2.       Mixture – A mixture is a material that contains two or more substances with their own distinct properties. Mixtures may be classified as:
a.       Solution – A homogeneous mixture. The dispersed particles in a solution may be molecules or ions. They mix uniformly with the particles of the solvent. In a solution, the component particles are too small to be seen.
b.      Colloid – The dispersed particles in a colloid are larger than those of a solution but, just the same, they are not visible to the naked eye. Hence, a colloid may look as if it were homogeneous and is often confused with a solution.
c.       Suspension – A heterogenous mixture which is also called as a solid in liquid mixture. The component particles in a suspension are large enough to be seen without a microscope.

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