1. The International System of Units
3.2
In the signs shown here, the distances are listed as numbers with no units attached. Without the units, it is impossible to communicate the measurement to others. When you make a measurement, you must assign the correct units to the numerical value.

2. Measuring with SI Units
3.2
Measuring with SI Units
The International System of Units (abbreviated SI), is a revised version of the metric system.

3. Measuring with SI Units
3.2
Measuring with SI Units
The five SI base units commonly used by chemists are
1. Length - the meter (m)
2. Mass - the kilogram (kg)
3. Temp - the kelvin (K)
4. Time – the second (s)
5. Amount - the mole (mol)

4. Volume
It is the amount of space something occupies
The SI unit of volume is the m3
A more convenient unit of volume for everyday use is the liter (L), a non-SI unit
1000 cm3 = 1 L
1 mL = 1 cm3

5. 3.2
Units and Quantities
The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL.
These photographs above give you some idea of the relative sizes of some different units of volume. a) The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL. b) A sugar cube is 1 cm on each edge and has a volume of 1 cm3. Note that 1 mL is the same as 1 cm3. c) A gallon of milk has about twice the volume of a 2-L bottle of soda. Calculating How many cubic centimeters are in 2 liters?

6. A sugar cube has a volume of 1 cm3. 1 mL is the same as 1 cm3.
3.2
Units and Quantities
A sugar cube has a volume of 1 cm3. 1 mL is the same as 1 cm3.
These photographs above give you some idea of the relative sizes of some different units of volume. a) The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL. b) A sugar cube is 1 cm on each edge and has a volume of 1 cm3. Note that 1 mL is the same as 1 cm3. c) A gallon of milk has about twice the volume of a 2-L bottle of soda. Calculating How many cubic centimeters are in 2 liters?

7. A gallon of milk has about twice the volume of a 2-L bottle of soda.
3.2
Units and Quantities
A gallon of milk has about twice the volume of a 2-L bottle of soda.
These photographs above give you some idea of the relative sizes of some different units of volume. a) The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL. b) A sugar cube is 1 cm on each edge and has a volume of 1 cm3. Note that 1 mL is the same as 1 cm3. c) A gallon of milk has about twice the volume of a 2-L bottle of soda. Calculating How many cubic centimeters are in 2 liters?

8. A measure of the amount of matter in an object
Units and Quantities
Mass
A measure of the amount of matter in an object
Measured in kg (SI base unit)
A gram (g) is 1/1000 of a kilogram; the mass of 1 cm3 of water at 4°C is 1 g.

9. Weight
a force that measures the pull on a given mass by gravity
An astronaut on the surface of the moon weighs 1/6 of what he weighs on Earth

10. Temperature is a measure of how hot or cold an object is.
3.2
Units and Quantities
Units of Temperature
Temperature is a measure of how hot or cold an object is.
Thermometers are used to measure temperature.
Thermometers are used to measure temperature. a) A liquid-in-glass thermometer contains alcohol or mineral spirits. b) A dial thermometer contains a coiled bimetallic strip. c) A Galileo thermometer contains several glass bulbs that are calibrated to sink or float depending on the temperature. The Galileo thermometer shown uses the Fahrenheit scale, which sets the freezing point of water at 32°F and the boiling point of water at 212°F.

11. 3.2
Units and Quantities
Scientists commonly use two equivalent units of temperature, the degree Celsius (˚C) and the kelvin (K).

12. 3.2
Units and Quantities
On the Celsius scale, the freezing point of water is 0°C and the boiling point is 100°C.
On the Kelvin scale, the freezing point of water is 273 K, and the boiling point is 373K.
The zero point on the Kelvin scale, 0 K, or absolute zero, is equal to 273°C.

13. 3.2
Units and Quantities
Because one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale, converting from one temperature to another is easy. You simply add or subtract 273, as shown in the following equations.

14. Conversions Between the Celsius and Kelvin Scales
3.2
Units and Quantities
Conversions Between the Celsius and Kelvin Scales
These thermometers show a comparison of the Celsius and Kelvin temperature scales. Note that a 1°C change on the Celsius scale is equal to a 1 K change on the Kelvin scale. Interpreting Diagrams What is a change of 10 K equivalent to on the Celsius scale?

15. Sample Problems
37˚C = ____ k
-20˚C = ____ k
100 k = ____ ˚C
340 k = ___ ˚C
310
253
-173 67

16. 3.2 Section Quiz. 1. Which of the following is not a base SI unit?
meter
gram
second
mole

17. 3.2 Section Quiz.
2. A temperature of 30 degrees Celsius is equivalent to
303 K.
300 K.
243 K.
247 K.