CHM 115 Lecture Notes - Lecture 1: Endothermic Process, Nitric Oxide, Significant Figures
Chemistry 115 Unit 1 Lecture 1
What is Chemistry?
• The study of matter (has mass, occupies space):
o The composition of matter
o How different types of matter interact with each other.
o How matter interacts with energy
• What types of data can tell us about the composition of a substance?
o Melting/Boiling Points
o Graphs - visual representations of data that tell us something about the composition of
matter
Significant Figures: The number of digits we can report for data gathered during an experiment is
limited by the type of instrument we use.
How many significant figures are in a number?
1. If the number contains a decimal:
a. Draw an arrow from left to right
i. Ex: 8230.1 = 5 sig figs
2. If the number doesn’t contain a decimal:
a. Draw an arrow right to left. The zeros at the end do not count
i. Ex: 232000 = 3 sig figs
Operations and Sig Figs
• Adding and Subtracting:
o Go with whichever one has the least numbers after the decimal place.
▪ Ex: 6.01 + 70.10 + 9.123 = 85.24
▪ Multiplying and Dividing:
o Go with whichever one has the least number of sig figs.
▪ Ex: (9.67 + 2.01) * 1.02 = 11.9
How different types of matter interact with each other
▪ The Law of Conservation of Matter:
o matter cannot be created or destroyed
▪ Basic building blocks of matter: atoms
o Atoms: Smallest particle of an element
How different types of matter interact with each other
Balancing Equations
• Select the most complicated formula and balance those atoms first.
• Start with those atoms that occur in only one molecule on each side.
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