CHEM 111 Study Guide - Midterm Guide: Decimal Mark, Significant Figures, Chemical Compound
13 Jun 2018
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Chapter 1: Classification of Matter,
Units and Measurements, Unit Conversions
Element: Simplest type of matter, it is a pure substance that cannot be broken down
or separated into a simpler substance.
Chemical compound: substance formed when 2+ elements are combined in a
defined ratio.
Pure substance: contains only one type of element or compound and has fixed
chemical composition.
Homogeneous mixtures: have a constant composition throughout
Heterogeneous mixtures:composition isn’t uniform
Physical properties: do not change the chemical composition of the material when
they are measured, although they may change the appearance
Chemical properties:involve a chemical change in the material, usually involves a
substance interacting with other materials
Rules for Significant Figures:
Non-zero digits = significant
Trailing 0’s are significant with numbers containing a decimal point (0.02500 has 4
sig figs), not in numbers without a decimal point (2500 only has two sig figs)
0’s at the beginning are not significant (the first two zeros in 0.02500)
Multiplication/division: answer has the same number of significant figures as the
measurement with the fewest significant figures.
Addition/subtraction: answer has the same number of decimal places present in the
numbers in the calculation.
Practice Questions
1.Classify each of the following substances as either an element or a compound:
a.Si: element
b. CO2: compound
2.Is boiling water a chemical property or a physical property? physical
What about baking bread? chemical
3.Classify each of the following as a pure substance, homogeneous mixture, or
heterogeneous mixture:
a.Copper wire pure substance
b. oil & vinegar salad dressing hetero
c. vinegar homo
4.Write the following numbers in scientific notation:
A.0.0000422 4.22x10^-5
b. 9700000000 9.7x10^9
5.Write the following number in standard notation:
a.7.22 x 106 7220000
b. 2.5 x 10-3 .0025
6.Identify the number of significant figures in the following numbers:
A.19.54 4
b. 0.0095 2
c. 1030 3
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Document Summary
Element: simplest type of matter, it is a pure substance that cannot be broken down or separated into a simpler substance. Chemical compound: substance formed when 2+ elements are combined in a defined ratio. Pure substance: contains only one type of element or compound and has fixed chemical composition. Physical properties: do not change the chemical composition of the material when they are measured, although they may change the appearance. Chemical properties:involve a chemical change in the material, usually involves a substance interacting with other materials. Trailing 0"s are significant with numbers containing a decimal point (0. 02500 has 4 sig figs), not in numbers without a decimal point (2500 only has two sig figs) 0"s at the beginning are not significant (the first two zeros in 0. 02500) Multiplication/division: answer has the same number of significant figures as the measurement with the fewest significant figures. Addition/subtraction: answer has the same number of decimal places present in the numbers in the calculation.
