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1.2 Notes Part B. Scientific Units. Unit Objectives. Use appropriate SI units for length, mass, time, temperature, quantity, area, volume and density. (ACT Quality Core I.A.2.b). SI Units. Le Système International d’Unités (SI) International System of Units in USA
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1.2 Notes Part B Scientific Units
Unit Objectives • Use appropriate SI units for length, mass, time, temperature, quantity, area, volume and density. (ACT Quality Core I.A.2.b)
SI Units • Le Système International d’Unités (SI) • International System of Units in USA • A modern version of the metric system based on a decimal system • Understood throughout the world • Each type of measurement has a base unit • Multiples of 10
Length • Distance between 2 points • SI base unit = meter (m). • Metric rulers and meter sticks are used to measure length
Mass • The quantity of matter in an object • SI Base Unit = gram (g) • NOT the same as weight • Weight = Newton (N) = measure of gravitational force on an object
Volume • The amount of space occupied by an object • Can measure volume of a solid, liquid, or gas • SI base unit is the liter, L • A liter occupies the same volume as a cubic decimeter, dm3. • 1 L = 1 dm3 • (1 mL = 1 cm3)
Measuring Volume • FOR Solids • Measure length, width, and height • Multiply the three numbers and their units together (V = l x w x h) • Volume = expressed in cubic centimeters, cm3
SI Units • Time = second (s) = interval between 2 events • Temperature = Kelvin (K) = measure of the average kinetic energy of particles in an object • Kelvin = °C +273 • °C = Kelvin - 273 • Example: 20 °C + 273 = 293 K
Time • Time is the interval between two events. • Or the time it takes for something to happen • SI unit for time = second(s)
Temperature • Measure of how hot or how cold something is. • For most scientific work, temperature is measured on the Celsius (C) scale. • On this scale, the freezing point of water is 0C, and the boiling point of water is 100C. • Between these points, the scale is divided into 100 equal divisions. Each one represents 1C.
Temperature • SI Unit = Kelvin (K). • Absolute Zero (0K) = coldest possible temperature • Absolute zero is equal to -273C which is 273 below the freezing point of water.
Finding Kelvin • Kelvin temperature can be found by adding 273 to the Celsius reading. • On the Kelvin scale, water freezes at 273 K and boils at 373 K. • To find Kelvin simply add 273 to the °C • K = °C +273 • To find Celsius, subtract 273 from the K • °C = Kelvin - 273
Temperature • These three thermometers illustrate the scales of temperature between the freezing and boiling points of water.
Density • Density is the mass per unit volume of a material • You find density by dividing an object’s mass by the object’s volume
Density = Derived Unit • SI Unit = g/cm3 • A combination of SI units. • A unit obtained by combining different SI units or multiply an IS unit by itself = a derived unit.
SI Units • Length = meters • Mass = grams • Time = seconds • Temperature = Kelvin • Volume = Liters, cubic centimeters • Density = g/mL, g/cm3
In-Class Assignment/Homework • Page 879 #1-4, 6-10 Math Problems • 1 m = 10 dm =100 cm = 1000 mm • 1 dm = 10 cm = 100 mm • 1 cm = 10 mm • 1 L = 1 dm3 • 1 mL = 1 cm3 • 1.2 reinforcement WKT