Transcript Unit 1 – Scientific Method and Introduction to Chemistry

Objectives
• Calculate the density of a sample using
mass and volume.
• Solve problems in chemistry
• Convert quantities using appropriate
conversion factors (metric units, time,
density)
Properties of Matter
•
Density –
– The ratio
of mass to volume:
m
D
V
m
D
V
– Examples:
1. What is the density of a sample with a mass of 24.9
g and a volume of 11.8 cm3?
2. What is the mass of a sample with a volume of 35.9
mL and a density of 2.18 g cm-3?
Problem-Solving
1. Analyze – Determine what information is
known, and what information needs to be
determined. Plan your solution.
2. Calculate – Follow your plan and develop
a solution. (remember sig figs)
3. Evaluate – Does the answer make
sense?
Conversions – Dimensional
Analysis
• Conversion factor –
– A ratio of equivalent measurements.
• Examples:
1000m
1 km
6.0221023 atom s
1 m ol
60 sec onds
1 min ute
• Use conversion factors to convert from one unit
to another. The unit to be “cancelled” goes on
the bottom of the conversion factor, and the unit
to which you are converting goes on the top.
• Sometimes you will need to make multiple
conversions to solve a problem.
Examples
1. Convert 1.5 m to cm.
2. Convert 0.00064 km to mm.
3. Convert 3.86 years to seconds.
4. Convert 3.79 m/s to km/h.