1. BELL RINGER
Consider the burning of gasoline and the evaporation of gasoline. Which process represents a chemical change and which represents a physical change? Explain your answer.

2. TOPIC II
Review

3. Atoms and Molecules Element
Atom: smallest part of an element that is still that element.
Molecule: Two or more atoms joined and acting as a unit.
Element
A substance that cannot be broken down into other substances by chemical methods.
All of the matter in the world around us contains elements.
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4. Periodic Table Vertical columns: groups, or families.
Elements with similar chemical properties.
Horizontal rows: Periods.
Physical and chemical properties change.

6. Compound Pure Substances Mixtures
It can be broken down into original elements by chemical methods.
It always has the same composition.
Pure Substances
They always have the same composition and are formed by chemical processes.
Mixtures
Can be separated into pure substances: elements and/or compounds using physical processes.
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7. Heterogeneous Mixture
Homogeneous Mixture
Same throughout.
Having visibly indistinguishable parts.
A solution.
Heterogeneous Mixture
It has visibly distinguishable parts.
Contains regions that have different properties from those of other regions.

8. Classification of Matter
Physically
Chemically

9. Properties and Changes in Matter
Intensive properties do not depend on the amount of matter present.
melting point
boiling point
density
ability to conduct electricity
ability to transfer energy as heat

10. Properties and Changes in Matter
Extensive properties depend on the amount of matter that is present.
volume
mass
the amount of energy in a substance.

11. Physical and chemical properties
Physical property: Characteristic that can be observed or measured without changing the identity of the substance.
Chemical property: Substance’s ability to undergo changes that transform it into different substances.

12. Methods of Separating Mixtures
Magnet: separate a magnetic substance from a non-magnetic substance.
Filtration: separate an insoluble substance from a soluble substance.
Chromatography: separation of complex mixtures that rely on the differential affinities of substances.
Distillation: Separate substances that have different boiling points

13. Accuracy and Precision
Reliability of measurements is expressed in terms of precision and accuracy.
Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured.
Precision refers to the closeness of a set of measurements of the same quantity made in the same way.

14. If less than 5%, then measurement is accurate
Accuracy can be expressed as Percentage Error
If less than 5%, then measurement is accurate

15. Uncertainty in measurements
A digit that must be estimated in a measurement.
It depends on the precision of the measuring device.
Significant Figures
Measured values are reported in terms of significant figures.
Consist of all the digits known with certainty plus one final digit, which is estimated.
Insignificant digits are never reported.

16. Rules for determining significant figures
The Digits
Digits That Count
Example
# of Sig Figs
Non-zero digits
ALL
         4.337 4
Leading zeros
(zeros at the BEGINNING)
NONE
         2
Captive zeros
(zeros BETWEEN non-zero digits)
         7
Trailing zeros
(zeros at the END)
ONLY IF they follow a non zero AND
there is a decimal
point in the number
but 8900
Leading, Captive AND Trailing Zeros
Combine the
rules above
but 3020 3
Scientific Notation
        7.78 x 103

17. Calculating With Sig Figs
Type of Problem
Example
MULTIPLICATION/DIVISION:
Find the number that has the fewest sig figs. That's how many sig figs should be in your answer.
3.35 x mL = mL rounded to 15.6 mL
3.35 has only 3 significant figures, so that's how many should be in the answer.  Round it off to 15.6 mL
ADDITION/SUBTRACTION:
Find the number that has the fewest digits to the right of the decimal point. The answer must contain no more digits to the RIGHT of the decimal point than the number in the problem.
64.25 cm cm = cm rounded to cm
64.25 has only two digits to the right of the decimal, so that's how many should be to the right of the decimal in the answer. Drop the last digit so the answer is cm.