Appendix 1 - Measurements
• We make QUALITATIVE
observations of reactions —
changes in color and physical
state.
• We also make QUANTITATIVE
MEASUREMENTS, which involve
numbers.
–Use SI units —(International
System of Units) based on the
metric system
Standards of Measurement
When we measure, we use a measuring tool to
compare some dimension of an object to a standard.
For example, at one time the
standard for length was the
king’s foot. What are some
problems with this standard?
Some Tools for Measurement
Which tool(s)
would you use to
measure:
A. temperature
B. volume
C. time
D. weight
Learning Check
Match
L) length
M) mass
V) volume
M A.
____
A bag of tomatoes is 4.6 kg.
L B.
____
A person is 2.0 m tall.
M C.
____
A medication contains 0.50 g Aspirin.
V
____ D. A bottle contains 1.5 L of water.
S.I. Measurement
Based on:
- number
- units
- accuracy report
S.I. Units are:
- related by factors of 10
* Table C of Reference Tables
Metric Prefixes
• Kilo- 10
3
3
or 1 kilometer = 10 m
1 km
or
10 3 m
• Centi- 10
-2
100 cm
1m
1000 m
1 km
or 100 centimeters = 1 meter
or
1m
100 cm
• Milli- 10 -3 or 1000 mm
1m
Metric Prefixes
Base Units
• Length = meter (m)
• Mass = kilogram (kg) also gram (g)
Mass vs. Weight
Mass: Amount of Matter
Weight: Force exerted by
the mass, only present
with gravity
Temperature
• Kelvin (K)
• Measure of the average
kinetic energy
*Thermometer is a
molecular speedometer.
Shows vibrational
energy.
• Table T of
Reference Tables
Time
The base unit for time = seconds (s)
60 seconds = 1 minute = 1/60 hour
Amount of a Substance
• Measured in moles (mol)
• Contains Avogadro’s number of
particles
23
• 6.02 X 10
• 602,000,000,000,000,000,000,000
Derived Units - Volume
•
•
•
•
Liter (L)
Volume = L X W X H
3
1cm X 1cm X 1cm = cm or 1ml
1dm X 1dm X 1dm = dm3 or 1L
Derived Units – Heat Energy
• Joules (J)
• 4.18 J = the energy needed to raise the temperature of 1
gram of water 1 degree K.
• Table B of Reference Tables – Specific Heat of Water
Heat (q) = 4.18J/gK X g (water) X
t
Heat Energy
• Suppose that a calorimeter contains 200. grams of
water at 294.0 K. As an exothermic reaction occurs
the water temperature rises to 314.0 K.
• What is the quantity of heat transferred?
1. Temperature change of 20.0 K for 200g water.
2. q= 4.18 J/gK X 200g X 20.0 K
3. q= 16,720 J or 16.7 KJ
1 calorie = 4.18 Joules
Pressure
• Pascal (Pa)
• Pa =
force
unit area
• Table A of Reference Tables
• 1 atm = 101.3 kPa
Density
• Table T of Reference Tables
• Solve for m
DXV=m
• Solve for V = m
D
Density Practice
1. What is the density of an object with a mass
3
of 20.1g and a volume of 142.5cm ?
1. What is the mass of an object with a density
of 32.1 g/cm3 and a volume of 10.0cm 3 ?
2. What is the volume of an object with a mass
of 40g and a density of 10g/cm3 ?