Standards of Measurement

Units and Standards Standard: an exact quantity that people agree to use to compare measurements SI = Systeme Internationale d’Unites All SI standards are universally accepted and understood by scientists throughout the world

SI Units All SI units have a base unit: SI Base Units: Quantity Measured Unit Symbol Length Meter m Mass Kilogram kg Time Second s Electric Current Ampere A Temperature Kelvin K Amount of substance Mole mol Intensity of light Candela cd

King Henry Died ….??? All other SI units are based off the base unit using prefixes Prefix King Kilo Henry Hecto Died Deka By BASE Drinking Deci Chocolate Centi Milk milli

Convert 12.54 kilometers to centimeters The answer is 1254000 centimeters

457 milliliters to hectoliters The answer is 0.00457 hL

Converting between SI units How do you convert 1.255L to milliliters?

Measuring distance Length is the distance between two points The size of the unit you measure will depend on the size of the object being measured

Measuring Volume Volume: amount of space occupied by an object Measuring a cube or rectangular prism: height x width x depth = volume ( L x w x h = V ) Example: 4 cm x 5 cm x 10 cm = 200 cm3 all measurements must be in the same unit Units will be those used for distance but cubed cm3 mm3 m3 etc.

Volume cont. To measure the volume of a liquid you measure them in a container.

Measuring Mass Mass is a measurement of the quantity of matter in an object Is measured in grams, milligrams, kg, etc. Density is the mass per unit volume of a material To find density, you divide an objects mass by it’s volume Example: 15 mg/mL, 20 g/cm3

Derived units A unit obtained by combining different SI units is called a derived unit. An SI unit multiplied by itself is also a derived unit Examples: m3 (volume) g/cm3 (density) or g/mL (density)

Measuring Time Time is the interval between two events SI unit for time is the second

Temperature 3 temperature scales: Celsius – 0oC is water freezes, 100oC is water boils Kelvin – 0 K is absolute zero, water freezes at 273 K and boils at 373 K No degree symbols are used SI unit for temperature Fahrenheit – 32oF is water freezes, 212oF water boils

Graphing A graph is a visual display of information or data Line graph shows any relationship where the dependent variable changes due to a change in the independent variable (often shows changes over time)

Bar graphs Bar graph is useful for comparing information collected by counting Dependent variable goes on y axis Independent variable goes on the x axis

Circle Graphs Also called a pie graph Circle graph is used to show how some fixed quantity is broken down into parts