Chapter 2 Notes II

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Chapter 2 Notes II

• CHEMICAL AND PHYSICAL CHANGES

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IV. Scientific Method

• The process researchers use to carry out their
  investigations. It is a logical approach to
  solving problems.

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A. Steps

• Ask a question
• Observe and collect data
• Formulate a hypothesis (a testable if-then
  statement). The hypothesis serves as a basis for
  making predictions and for carrying out further
  experiments.
• Test your hypothesis Requires experimentation
  that provides data to support or refute your
  hypothesis.

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B. Terms to Know

• 1.      Law vs. theory
• Scientific (natural) Law a general statement
  based on the observed behavior of matter to which
  no exceptions are known.
• Theory a broad generalization that explains a
  body of facts or phenomena.

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1. Quantitative vs. qualitative data

• Quantitative numerical (mass, density)
• Quantity - number unit
• Qualitative descriptive (color, shape)

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Chemistry the study of MATTER

• I. Chemistry The branch of science that deals
  with the identification of the substances of
  which matter is composed the investigation of
  their properties and the ways in which they
  interact, combine, and change and the use of
  these processes to form new substances.
• (Matter anything that has mass and takes up
  space)

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PROPERTIES OF MATTER

• What is matter?
• What is mass?

Anything that has mass and takes up space
The amount of matter an object contains
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Chemical Compositionmixture or pure
substance?

• Before we can even begin to consider matter from
  a chemical point of view, we need to know
  something about its composition is the stuff I
  am looking at a single substance, or is it
  a mixture? Think of a sample of salt (sodium
  chloride) as opposed to a solution of salt in
  water a mixture of salt and water.

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SUBSTANCES

• A substance is matter that has a definite and
  uniform composition

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MIXTURES

• A mixture is a physical blend of two or more
  substances. They can be physically separated.
  How?

One type of stuff
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HETEROGENEOUS vs. HOMOGENEOUS

• There are two different types of mixtures.
• A heterogeneous mixture is one that has more than
  one phase (part of uniform composition)
• A homogeneous mixture has only one phase.

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CuSO4 Solution
Orange Juice
Oil and Water

• Mixtures matter that can be physically separated
  into component parts (pure substances).
• a. homogeneous mixture has uniform composition
  also called a solution
• b. heterogeneous mixture does not have a
  uniform composition

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MIXTURES
physically
separable
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HETEROGENEOUS OR HOMOGENEOUS?

• Saltwater
• Spaghetti sauce
• Muddy water
• Cough syrup
• Salad
• Brass

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TYPES OF SUBSTANCES

• There are two different types of substances

ELEMENTS
AND
COMPOUNDS
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ELEMENTS

• An element is the simplest forms of matter.

• Each element is represented by a chemical symbol.

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COMPOUNDS

• A compound is a substance that can be separated
  into simpler substances only by chemical means

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CuSO4
Cu

• Pure Substances when component parts of a
  mixture can no longer be physically separated
  into simpler substances. Pure substances are
  either compounds or elements.
• a. Compounds can be decomposed by a chemical
  change. Two or more elements bonded together.
• b. Elements cannot be decomposed by a chemical
  change. Will appear no the periodic table.

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TYPES OF MATTER
physically
separable
chemically
separable
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III. Classification of Matter

• Matter
• Can it be physically separated?
• Yes
  No
• Mixtures Pure Substances
• Is the composition uniform? Can it be decomposed
  by an ordinary chemical reaction?
• Yes No Yes
  No
• Homogeneous Heterogeneous Compounds
  Elements
• Mixtures Mixtures (water, sodium
  (gold, oxygen,
• (Solutions) (Suspensions chloride, sucrose)
  carbon)
• (air, sugar water, or Colliods)
• salt water) (granite, wood,
• muddy water)

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Techniques used for mixture separation

• Filtration (sand from water)
• Centrifugation (butterfat from milk)
• Evaporation (salt from water)
• Distillation (water from salt)
• Chromatography (separating pigments in ink)  
•  

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Filtration (sand from water)
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Centrifuge Solid or liquid particles of
different densities are separated by rotating
them in a tube in a horizontal circle. The dense
particles tend to move along the length of the
tube to a greater radius of rotation, displacing
the lighter particles to the other end.
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Evaporation (salt from water)

•  

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• Distillation
• A liquid is partly boiled away the first
  portions of the condensed vapor will be enriched
  in the lower-boiling component.
•  
•  

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Chromatography As a liquid or gaseous mixture
flows along a column containing an adsorbent
material, the more strongly-adsorbed components
tend to move more slowly and emerge later than
the less-strongly adsorbedcomponents.  
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Liquid-liquid Extraction 

• Two mutually-insoluble liquids, one containing
  two or more solutes (dissolved substances), are
  shaken together. Each solute will concentrate in
  the liquid in which it is more soluble.

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PHYSICAL PROPERTIES

• A quality or condition of a substance that can be
  observed or measured without changing the
  substances composition
• What are some examples?

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II. Physical Properties of Matter
Physical properties of matter are categorized as
either Intensive or Extensive

• Intensive - Properties that do not depend on the
  amount of the matter present.
• Ex Color, Odor, Luster, Malleability,
  Ductility, Conductivity, Hardness,
  Melting/Freezing Point, Boiling Point, Density
•  Extensive - Properties that do depend on the
  amount of matter present.
• Ex Mass, Volume, Weight, Length

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STATES OF MATTER

• Matters state is a physical property

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SIDENOTE

• A gaseous substance that is found as a solid or
  liquid at room temperature is called vapor.

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PHYSICAL CHANGES

• A physical change is one that does not involve
  altering the chemical composition.

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CHEMICAL REACTIONS

• The ability of a substance to react and form new
  substances is called a chemical property.
• In a chemical reaction, one or more substances
  change into new substances.
• A reaction starts with the reactants, and the
  substances formed are called products.

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4 CLUES TO CHEMICAL REACTION
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CHEMICAL OR PHYSICAL CHANGE?

• Baking cookies
• Boiling water
• Dissolving salt
• Burning firewood
• Milk spoiling
• Metal rusting
• Tearing paper
• Melting ice

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LAW OF CONSERVATION OF MASS

• During any chemical reaction, the quantity of
  matter is unchanged. The mass of the products
  always equals the mass of the reactants.