Introduction to Matter Chemistry & Classifying Matter...
Transcript of Introduction to Matter Chemistry & Classifying Matter...
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Introduction to Chemistry &
Classifying Matter (Section 2.1)
Matter
• Anything that has mass and takes up space
• Comes in many different forms
Mass • A measurement reflecting
the amount of matter • Mass and weight are not the
same o Weight measures the
earth’s gravitational pull on
matter
Chemistry at Different Levels
• Macroscopic (very large) to Sub-Microscopic level (very small)
• Chemistry explains how changes at the sub-microscopic level lead to changes at the macroscopic level
Stuff
Matter
Elements
Particles
Atoms
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Classifying Matter
• Based on their compositions, materials can be divided into pure substances and mixtures
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Pure Substances • Matter that always has exactly the same
composition • Every sample of a given substance has the
same properties because a fixed, uniform composition
• Substances can be classified into two categories o Elements o Compounds
Elements • A substance that cannot be broken down into
smaller, simpler substances • An atom is the smallest particle of an element • An element has a fixed composition because it
contains only one type of atom o No two different elements contain the same type of atom
• 91 naturally occurring elements, plus others developed in the lab
• Each element has a unique name and symbol
• Are not equally abundant
Symbols for Elements • Symbols for elements are either
one or two letters • The first letter is always
capitalized and the second letter is not
• Symbols allow scientists from different countries to communicate without confusion
• Examples: o Aluminum = Al o Hydrogen = H o Calcium = Ca o Silver = Ag
Compounds • Is a substance that is made from two
or more simpler substances and can be broken down into those simpler substances
• A compound always contains two or more elements joined in a fixed proportion
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Mixtures • A combination of two or more
pure substances, in which each pure substance retains its individual properties
• Heterogeneous Mixtures o Does not blend smoothly o Individual substances remain
distinct • Homogeneous Mixtures o Constant composition
throughout
Solutions, Suspensions, &
Colloids • The size of the particles in a mixture have
an effect on the properties of the mixture • Based on the size of its largest particles, a
mixture can be classified as a solution, a suspension, or a colloid
Solutions • Formed when substances dissolve and form a
homogeneous mixture • The particles in a solution are too small to settle out of
the solution, be trapped by a filter, or scatter light o They do not separate into distinct layers o None of the substances get trapped when
passed through a filter o Light can pass through without being scattered in all directions
Suspensions • Is a heterogeneous mixture that
separates into layers over time • Suspended particles settle out
of a mixture or are trapped by a filter (larger particles than that in the solution)
• Suspensions are cloudy because the larger particles can scatter light in all directions
Colloids
• Contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension
• Does not separate into layers • Cannot use a filter to separate parts • Light is scattered when going through a colloid o The scattering of light is a property that can
be used to distinguish colloids and suspensions from solutions
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