1. Scientific Measurement Measurements and Their Uncertainty
Chapter 3
Scientific Measurement
Section 3.1
Measurements and Their Uncertainty

2. A single gram of hydrogen contains about:
602,000,000,000,000,000,000,000 hydrogen atoms
Writing such a number like this will be confusing and there will be a big probability for making mistakes.
To make our life easier, we can use the scientific notation, which is a product of two numbers:
The first one is a coefficient and the other is 10 raised to
a power.
e.g. the number which is written above can be written as follows:

3. Significant Figures
All of the digits that are known and the last digit that is estimated.
Rules for determining whether a digit is significant:
1. Every nonzero digit is significant. ,
2. Zeros appearing between nonzero digits are significant. ,
3. Leftmost zeros appearing in front of nonzero digits are
not significant. ,
4. Zeros at the end of a number and to the right of a
decimal point are significant. ,
5. Zeros at the rightmost end that lie to the left of a
decimal point are not significant.
300 ,

4. Round the answer to the least decimal place.
How to Round Numbers
If the next place value is 5 or more, increase the value in the last retained place by 1
If the next place value is less than 5, the value in the last retained place stays the same.
Addition & Subtraction:
Round the answer to the least decimal place.
Multiplication & Division:
Round the answer to the least significant figures.

5. Classwork:
# 1 & 2 , page: 68
# 3 , page: 69

6. The International System of Units
Section 3.2
The International System of Units

7. The Five SI basic units commonly used by chemists are:
Symbol
Quantity
Meter m
Length
Kilogram kg
Mass
Kelvin K
Temperature
second s
Time
mole
mol
Amount of substance

8. Commonly Used Metric Prefixes
1000
Mega 10
(M)
kilo 10 10
hecto
(k)
deka 10
(h) 10
(da)
Unit 10
meter
gram
Second
Liter
deci
1000
centi
(d)
milli
(c)
1000
(m)
micro
1000
(µ)
nano
1000
(n)
pico
(p)
To convert a quantity to a larger unit, multiply by 10 - power
femto
(f)
To convert a quantity to a smaller unit, multiply by 10 + power

9. Units of Temperature
Scientists commonly use two equivalent units of temperature, the degree Celsius and the Kelvin.
The Celsius scale sets the freezing point of water at 0°C and the boiling point of water at 100°C.
The Kelvin scale sets the freezing point of water at 273 K and the boiling point is 373 K
The zero point on the Kelvin scale, 0 K is called, absolute zero.
K = °C + 273
°C = (°F - 32) ÷ 1.8
°C = K - 273
°F = (°C x 1.8) + 32

10. Classwork:
# 32 & 33 , page: 84

11. Section 3.4
Density

12. mass Density = volume Density
is the ratio of the mass of an object to its volume.
mass
Density =
volume
It is an intensive property that depends only on the composition of a substance, not on the size of the sample.
What do you think will happen if the corn oil is poured into a beaker of water?
The oil floats on the top of water, why??
The density of oil is less than the density of water.
Look at Table 3.6 on page 90

13. If you heat an object, like a piece of iron, what do you notice?
It increases in volume, but the mass remains the same.
mass
According to the density law,
Density =
volume
So when the temperature increases, the volume will increase and as a result the density will decrease.
Exception for this conclusion is water
By decreasing the temperature the volume will increase. So the density will decrease.
e.g. ice water floats on liquid water.
Why??

14. Classwork:
# 55 & 56 , page: 93