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Measurement Using the International System (SI)

Measurement Using the International System (SI). Key question: What are the basic units of measurement in the SI system?. SI System. The standard system used by scientists is the SI system. Scientists use SI units to measure length, volume, mass, density, and temperature.

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Measurement Using the International System (SI)

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  1. Measurement Using the International System (SI) Key question: What are the basic units of measurement in the SI system?

  2. SI System • The standard system used by scientists is the SI system. • Scientists use SI units to measure length, volume, mass, density, and temperature. • KHDBDCM : easy way to remember how to convert your units.

  3. Length • Basic unit of length in the SI system is meter (m). • Centimeter (cm) – one-hundredth • Millimeter (mm) – one thousandth • Kilometer (km) – kilo means 1000 • 1 meter = 100 cm • 1 meter = 1000 mm • 1000 meters = 1 km

  4. Volume • Volume is the amount of space an object takes up. • The basic unit of volume is the liter (L). • Milliliter (mL) – used to measure volumes smaller than a liter. • Liters and milliliters are used to measure the volume of liquids. • The SI unit used to measure the volume of solids and the liquids in shots is called cubic centimeters (cm³) or (cc) • A cubic centimeter is equal to a milliliter.

  5. Volume • Cubic centimeters are often used in meauring the volume of liquids as well as solids. • 1 liter (l) = 1000 milliliters (ml) or 1000 cubic centimeters (cm³)

  6. Mass • Basic unit of mass in the SI system is the kilogram (kg). • Mass is the amount of matter in an object. • A kilogram (kg) is about 2.2 pounds. • What is your mass in kilograms? • Gram (g) – used to measure smaller objects • Milligrams (mg) – used to measure even smaller objects.

  7. Mass • 1 kilogram (kg) = 1000 grams (g) • 1 gram = 1000 milligrams (mg) • 1000 kilograms = 1 metric ton

  8. Density • Density is defined as the mass per unit volume of a substance. • Density = mass ÷ volume • Suppose a substance has a mass of 10 grams and a volume of 10 milliliters. If you divide the mass of 10 grams by the volume of 10 mL you obtain the density: • D= 10 g ÷ 10 mL = 1 g/mL

  9. Temperature • Three common scales for measuring temperature Fahrenheit, Celsius, and Kelvin. • In Fahrenheit, there are 180 degrees between the boiling point and the freezing point of water. Boiling point of water = 212, freezing point of water = 32, body temperature = 98.6, room temperature = 68

  10. Temperature • In the SI system, temperature is measured on the Kelvin or Celsius scales. • Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius. • Normal body temperature in humans is 37ºC . • Comfortable room temperature is about 21ºC.

  11. Temperature • For the Kelvin scale, the boiling point of water is 373.15 K, freezing point = 273.15K, body temp = 310.15K , and room temp = 293.15 K • O Kelvin, a.k.a. “absolute zero” is the point at which all molecular motion stops

  12. Dimensional Analysis • Dimensional analysis is the skill of converting one unit to another. • Dimensional analysis involves determining in what units a problem is given, in which units the answer should be, and the factor to be used to make the conversion from one unit to another. • To perform dimensional analysis, you must use a conversion factor. • A conversion factor is a fraction always equal to 1.

  13. Dimensional Analysis • 1000 grams = 1 1 kilogram 1kilogram or 1000 grams = 1 • Which conversion factor should you use to change 2500 grams into kilograms? • 2500 grams x 1 kilogram 1000 grams • Next, cancel out the same units • Next step is multiply: 2500 x 1 kilogram 1000 Which equals 2500 kilogram 1000 = 2.5 kilograms

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