1. Lecture 3 Units and Measurements Ozgur Unal
NIS – CHEMISTRY
Lecture 3
Units and Measurements
Ozgur Unal

2. NIS – CHEMISTRY List SI base units and state how each unit is defined.
Calculate the density of an object with given mass and volume.
Determine the density of an object using water displacement method.

3. Units and Measurements
The measurement of any quantity is made relative to a particular standard or unit.
For centuries units of measurement were not exact.
International System of Units (SI) system of units accepted in 1960.
SI, is based on multiples of ten.

4. Base Units A base unit must be defined in terms of a standard.
SI has 7 base units.
All other units are derived from base units. For example: density (kg/m3), unit of speed (m/s), unit of energy (Joule)

5. SI BASE UNITS Measuring time:
It is sometimes necessary to measure the amount of time between events (just like you did yesterday with hard and soft water samples).
SI unit of time is second (s).
Measuring length:
Length is the distance between two points.
In SI, we use meter (m) to measure distances.
Measure the length of your pencil using your rulers

6. SI BASE UNITS Measuring matter:
Mass is a measurement of the quantity of matter in an object.
Unit of mass in SI is kilograms (kg)
Measuring temperature:
Temperature tells you how hot or cold an object is.
Different units for temperature (Celsius, Kelvin, Fahrenheit).
SI unit of temperature is Kelvin (K).
In K scale, water freezes at 273 K and boils at 373 K.
You can convert between units doing some calculations.

7. Derived Units Measuring volume:
Volume is the amount of space occupied by an object.
For objects with regular sizes (such as a brick), you can calculate the volume.
Volume of a liquid is expressed in liters.
1 L = 1 dm3
Density
Density is the mass per unit volume of a material.
density = mass / volume
Perform Minilab on page 39

8. Lecture 4 Scientific Notation and Unit Conversion Ozgur Unal
NIS – CHEMISTRY
Lecture 4
Scientific Notation and Unit Conversion
Ozgur Unal

9. How old do you think the objects in the pictures are?
SCIENTIFIC NOTATION
How old do you think the objects in the pictures are?
In science, scientific notation is used to write the numbers that are:
Too big, such are the age of the universe..
Too small, such as the size of an atom

10. SCIENTIFIC NOTATION
Scientific notation expresses any number as a number between 1 and 10 (coefficient) multiplied by 10 raised to a power (exponent)
Example: Carbon atoms in the hope diamond,
4.6 x 10^23
Mass of one carbon atom,
2 x 10^-23
More examples:
4,500,

11. Operations with Scientific Notation
Addition and Subtraction: In order to add or subtract numbers written in scientific notation, the exponents must be the same.
(7.35x10^2 m) + (2.43x10^2 m) = 9.78x10^2
More examples in the textbook!
Multiplication and Division: Two step process.
1- Multiply (divide) the coefficients for multiplication (division)
2- Add (subtract) the exponents for multiplication (division)

12. Operations with Scientific Notation
Multiply 4.6 x 10^23 and 2 x 10^-23
1- Multiply the coefficients
4.6*2 = 9.2
2-Add the exponents
23+ (-23) = 0
The answer is 9.2 x 10^0 = 9.2
Divide 9 X 10^8 by 3 X 10^5…
1- Divide the coefficients: 9 / 3 = 3
2- Subtract the exponent in the divisor from the exponent in the dividend: 8 – 5 = 3
The answer is 3 x 10^3

13. Unit Conversion How do we convert 60 miles/hr to m/s?
When converting one unit to another, we use conversion factors.
Example: Convert 5 m to cm.
Use the conversion factor 1 m = 100 cm
5m = 5 * 1 m = 5 * 100 cm = 500 cm
Convert 15 miles to km:
Conversion factor: 1 mile = km
15 miles = 15 * 1 mile = 15 * km = km