The International System of Units
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End Show © Copyright Pearson Prentice Hall Slide 1 of 33 3. 2 The International System of Un 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.
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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. 3.2. - PowerPoint PPT Presentation
Transcript of The International System of Units
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Slide 1 of 33
3.2 The International System of Units
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.
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Slide 2 of 33
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The International System of Units
>3.2 Measuring with SI Units
The International System of Units (abbreviated SI), is a revised version of the metric system.
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Slide 3 of 33
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The International System of 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)
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Slide 4 of 33
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The International System of Units
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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
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Slide 5 of 33
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The International System of Units
>3.2 Units and Quantities
The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL.
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Slide 6 of 33
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The International System of Units
>3.2 Units and Quantities
A sugar cube has a volume of 1 cm3. 1 mL is the same as 1 cm3.
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The International System of Units
>3.2 Units and Quantities
A gallon of milk has about twice the volume of a 2-L bottle of soda.
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Slide 8 of 33
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The International System of Units
> 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.
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Slide 9 of 33
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The International System of Units
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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
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Slide 10 of 33
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The International System of Units
>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.
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Slide 11 of 33
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The International System of Units
>3.2 Units and Quantities
Scientists commonly use two equivalent units of temperature, the degree Celsius (˚C) and the kelvin (K).
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The International System of Units
>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.
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Slide 13 of 33
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The International System of Units
>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.
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Slide 14 of 33
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The International System of Units
>3.2 Units and Quantities
Conversions Between the Celsius and Kelvin Scales
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Slide 15 of 33
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The International System of Units
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Sample Problems
1)37˚C = ____ k
2)-20˚C = ____ k
3)100 k = ____ ˚C
4)340 k = ___ ˚C
310
253
-173
67
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Slide 16 of 33
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3.2 Section Quiz.
1. Which of the following is not a base SI unit?
a. meter
b. gram
c. second
d. mole
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Slide 17 of 33
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3.2 Section Quiz.
2. A temperature of 30 degrees Celsius is equivalent to
a. 303 K.
b. 300 K.
c. 243 K.
d. 247 K.
