1. Introduction to General Chemistry Part 2:
Units
Ch. 1

2. Qualitative and Quantitative Analysis
In chemistry, the scientific method is used to investigate scientific phenomena & acquire new knowledge
Empirical evidence is gathered which supports or refutes a hypothesis
Empirical evidence is either quantitative or qualitative
Quantitative data is numerical, and results can be measured
Qualitative data is NOT numerical, but consists of observations and descriptions

3. Quantitative and Qualitative Analysis
A + B C
Quantitative data
How much C is formed?
How efficient is the reaction?
What is the rate of the reaction?
Qualitative data
What color is it?
Is it solid, liquid, gas?
How does it smell?

4. Units Quantitative measurements are represented by a:
NUMBER and a UNIT
A unit is a standard against which a physical quantity is compared physical quantity
Temperature is measured in Co, Ko,or Fo
Currency is measured in $USD
Distance is measured in meters, miles, ft, etc.
Time is reported in seconds, minutes, hr, etc.
Internationally accepted system of measurements is called the SI unit system

5. SI Unit System: The Units of Physical Science

6. Greek Prefixes Prefixes indicate powers of 10
ex. k= 103; 5 kg = 5 x (103)g

7. A Review of Scientific Notation
Scientific notation indicates a factor (F) multiplied by a power (n) of 10
F x 10n
Important: All integers end with a decimal point, even though it is not commonly written (1  1. )
For all non integers, simply shift the decimal right n places
2.5 x 105 = x 108 =
For negative exponents, shift the decimal left. All values less than 1 have negative exponents.
7.141 x 10-2 = x 10-7 =
Convert to standard notation
x 104
8.971 x 10-3
6.50 x 100
Convert to scientific notation 15
125.3

8. Group Work
Convert the following values to grams in both standard and scientific notation.
421.4 kg mg
481 µg

9. Why Are Units Important? Example #1
In 1999, NASA lost the $125M Mars Orbiter System.
One group of engineers failed to communicate with another that their calculated values were in English units (feet, inches, pounds), and not SI units.
The satellite, which was intended to monitor weather patterns on Mars, descended too far into the atmosphere and melted.

10. Why Are Units Important? Example #2
In 1983, an Air Canada Plane ran out of fuel half way through its scheduled flight. Why?
Airline workers improperly converted between liters and gallons.
Luckily, no one died.

11. Derived SI Units: VOLUME
Many measured properties have units that are combinations of the fundamental SI units
Volume: defines the quantity of space an object occupies; or the capacity of fluid a container can hold
expressed in units of (length)3 or Liters (L)
1 L is equal to the volume of fluid that a cube which is 10 cm on each side can hold
10 cm
V = (10 cm)3 = 1000 cm3
1 L = 1000 cm3
1000 mL = 1000 cm3
mL = cm3

12. THE DENSITY OF WATER IS 𝟏 𝒈 𝒄𝒎 𝟑 𝒐𝒓 𝟏 𝒈 𝒎𝑳
Derived SI Units: DENSITY
All matter has mass, and must therefore occupy space. Density correlates the mass of a substance to the volume of space it occupies.
Density = mass per unit volume (mass/volume). Different materials have different densities.
Would a 20-gallon container filled with bricks have the same mass as an equivalent volume of feathers? NO!
THE DENSITY OF WATER IS 𝟏 𝒈 𝒄𝒎 𝟑 𝒐𝒓 𝟏 𝒈 𝒎𝑳

13. Group Work
A cubic container that is 25 cm on each side is filled with ethanol. The density of ethanol is 0.79 g/mL.
What is the volume of ethanol in the cube in mL?
What is the volume in L?
What is the mass of ethanol in kg?
Give answers in scientific notation!!

14. Derived SI Units: ENERGY
What is Energy?
Energy is defined as the capacity to perform “work”
How do we define work?
Work is defined as the action of applying a force acting over some distance. Work can not be done if no energy is available.
In SI units, we use the unit Joule (J) to represent energy.
𝐽= 𝑘𝑔 𝑚 2 𝑠 2

15. Conservation of Energy
Energy is never created or destroyed, merely converted between forms and transferred from place to place. The total energy of the universe is finite.

16. Forms of Energy
Energy comes in many forms and can be converted from one form to another. Some examples are given:
Chemical Energy
Energy stored in chemical bonds (e.g. gasoline, coal, etc.) that can be released by chemical reaction, typically combustion (fire)
Heat Energy (thermal energy)
Heat is defined as energy flow between bodies of matter resulting from collisions of molecules or random motions of electrons.

17. Forms of Energy Mass Energy
Energy and mass are interchangeable. During a fusion reaction (e.g. stars), mass is lost and energy is formed. This mass appears as energy according to the following:
where m is the change in mass (in kg), c is the speed of light, and E is the energy released (J). This is the basis of nuclear power.
Kinetic Energy
Energy of motion (e.g. a moving car). An object with mass m, moving at a velocity V (meters/sec) has kinetic energy:
𝐄=∆𝐦 𝐜 𝟐
𝐄 𝐤 = 𝟏 𝟐 𝐦 𝐕 𝟐

18. Forms of Energy Potential Energy
Potential energy corresponds to energy that is stored as a result of the position of mass in a field.
If a mass m is held at a height h (meters) above the ground, assuming a gravitational acceleration of 9.8 m/s2 (g), its potential energy is:
If the object is dropped, it loses potential energy. However, it speeds up as it falls, so its kinetic energy increases equally (conversion).
𝐄 𝐏 =𝐦𝐠𝐡

19. Forms of Energy Electrical Energy
Energy resulting from electric current, the movement of electrons through a conductive circuit. Electrical energy is a type of potential energy. For a charge q (coulombs, C) moving across a voltage, V
Light/Radiation
The energy of a wave of light is calculated as the product of Planck’s constant, h (J s), and the wave frequency, ν (1/s)
𝐄 𝐞𝐥𝐞𝐜 =𝐪𝐕
𝐄=𝐡𝐯

20. Power
It is often necessary to express the rate of energy usage. This is called power.
Typically, we speak in terms of energy per second. In SI units, a joule per second (J/s) is known as a watt (W).
𝐏𝐨𝐰𝐞𝐫= 𝐞𝐧𝐞𝐫𝐠𝐲 𝐭𝐢𝐦𝐞

21. Temperature
Temperature: a measure of the tendency of a substance to lose or absorb heat. Temperature and heat are not the same.
Heat always flows from bodies of higher temperature to those of lower temperature
The stove top is ‘hot’ because the surface is at a much higher temperature than your hand, so heat flows rapidly from the stove to your hand
Ice feels ‘cold’ because it is at a lower temperature than your body, so heat flows from your body to the ice, causing it to melt
Explain wind chill?

22. Temperature
When performing calculations in chemistry, temperature must always be converted to Kelvin (oK) units (unless otherwise stated).
The lowest possible temperature that can ever be reached is 0oK, or absolute zero. At this temperature, all molecular motion stops.
To convert temperatures to the Kelvin scale:
oK : oC