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MEASUREMENTS, UNITS, and TOOLS

MEASUREMENTS, UNITS, and TOOLS. “ I CAN ” statements. critique that data represented with a number alone is meaningless. [L3] This means that I can cite evidences that data must always be reported with its numerical value and its appropriate unit.

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MEASUREMENTS, UNITS, and TOOLS

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  1. MEASUREMENTS,UNITS, and TOOLS

  2. “I CAN” statements • critique that data represented with a number alone is meaningless. [L3]This means that I can cite evidences that data must always be reported with its numerical value and its appropriate unit. • distinguish between accurate and precise data [L2]This means that I can distinguish between data that are close to the accepted value and those that are all close to each other. • classify measurements as being fundamental (base), direct, or derived [L2]This means that I can relate a measurement to its specific unit. • recall visual aids for prefixes of mass and length [L1]

  3. “I CAN” statements • use the proper instruments to measure [L1] • length, • volume liquid, • mass • weight • temperatureThis means that I can adequately measure and report data/values obtained with __ a ruler, __ a graduated cylinder, __ a triple beam balance,__ a spring scale__ a thermometer

  4. “I CAN” statements • calculate area and volume solid [L1] • solve density problems [L2]This means that I can modify the formula for density in order to estimate either volume or mass • infer how liquids will layer in a mixture based on their densities [L2]

  5. “A science is as mature as its measurement tools”Louis Pasteur, 1822-1895 “To measure is to know” James Clerk Maxwell, 1831-1879

  6. Any data or value is expressed in terms of a NUMBER [magnitude, quantity] and a UNIT[describing the type of measurement] A number alone is MEANINGLESS

  7. ACCURACY vs. PRECISION ? ?

  8. ACCURACY vs. PRECISION ACCURATE measurement(s) is (are) close to the accepted values PRECISE repeated measurements are close to each other

  9. ACCURACY vs. PRECISION PRECISEBUT LOW ACCURACY

  10. HOW WOULD YOU REPRESENT? ACCURATE and PRECISE

  11. HOW WOULD YOU REPRESENT? NEITHER ACCURATE, NOR PRECISE

  12. In science, you must aim to collect data that are both accurate AND precise

  13. BASE/FUNDAMENTAL,“DIRECT”, and DERIVEDMEASUREMENTS

  14. Base and/or “Direct” Measurements A base unit is ALWAYS directly measured, but a direct measurement is not necessarily a base unit

  15. Time  second Mass  gram Temperature  Kelvin Length  meter

  16. LENGTH = Distance from one point to another The base unit for length is METER [m] • 1 kilometer [km] = 5 – 6 city blocks • 1 meter [m] = from floor to door handle • 1 centimeter [cm] = width of little finger • 1 millimeter [mm] = width of a dime / pencil lead NOTICE THE ABBREVIATIONS: prefix and unit

  17. 16 divisions per inch 1/16th 1/4 1/8th 1/2

  18. 10 divisions per centimeter 1/10th or 0.1cm or 1 mm

  19. State the same measurement in two different units Length 10 in. 260 mm 26.0 cm

  20. MASS [not to be confused with WEIGHT] = amount of MATTER that an object has or contains The base unit for mass is the GRAM [g] • 1 kilogram [kg] = house brick • 1 gram [g] = 1 small paper clip • 454 grams [g] = 1 pound NOTICE THE ABBREVIATIONS: prefix and unit

  21. Triple –beam Balance 80 200 0.6 • 6 200 + 80 + 6 + 0.6 = 286.6 grams

  22. 70 300 • 6 300 + 70 + 6 + 0.0 = 376.0 grams

  23. 30 300 • 4 0.5 300 + 30 + 4 + 0.5 = 334.5 grams

  24. TEMPERATURE = average kinetic energy of the particles in a substance, related to how hot or cold it is Fahrenheit °F Water boils 212 Scale of 180 Water freezes 32

  25. TEMPERATURE Metric System uses primarily Celsius [°C], but it is NOT the base unit Fahrenheit Centigrade °F °C Water boils 212 100 Scale of 180 Scale of 100 Water freezes 32 0

  26. TEMPERATURE SI unit Kelvin [K] = thermodynamic temp. Note no degree symbol for Kelvin Note 1 Kelvin = 1 °Celsius Fahrenheit Centigrade Kelvin °F °C K Water boils 212 100 373 0K is the absolute zero. Even the atoms are stopped Scale of 180 Scale of 100 Water freezes 32 0 273

  27. TEMPERATURE [˚C] 87.5°C 35°C

  28. Volume liquid can be “directly” measured with the proper instruments What could be used to evaluate the volume of a liquid? 2 Liters

  29. VOLUME LIQUID = Amount of SPACE that a liquid occupies The unit without prefix for volume liquid is LITER [L] • 4 liters [L] = 1 gallon • 355 milliliter [mL] = 12 ounces NOTICE THE ABBREVIATIONS: prefix and unit

  30. Graduated cylinder; 0 at the bottom 10 mL graduation 53 mL Always read the BOTTOM of the MENISCUS 1mL SO EACH SUB-DIVISION IS WORTH:

  31. What do you see?? 11.5 mL

  32. 76 mL

  33. 3.7 4.9 3.3

  34. 7.7 5.4 3.1

  35. 4.7 4.2 6.6

  36. DERIVED UNITS Units/Measurements that are found by making CALCULATIONS • AREA: the SURFACE of an objectFormula = Length x WidthExample: if you measure in meter, what will the unit be for the area?? NOTE: both dimensions / measurements must be in the same units

  37. 5 m The ‘derived’ unit is read as square meter or meter squared 10 m AREA = 5 m x 10 m = 50 m2 Numerical value

  38. DERIVED UNITS • VOLUME solid: the SPACE that an object occupies or contains.Formula = Length x Width x HeightExample: if you measure in centimeter, what will the unit be for the volume??

  39. 3 cm 5 cm 15 cm VOLUME = 3 cm x 5 cm x 15 cm = 225 cm3 The ‘derived’ unit is read as “cubic centimeter”… Numerical value

  40. VOLUME and LENGTH are linked 1 cubic centimeter = 1 milliliter 1 mL of any liquid occupies [fills] a small container measuring 1cm by 1cm by 1 cm 1 cm So 1mL is equivalent to 1cm3 1 cm 1 cm So 1 Liter (L) occupies ???? cm3

  41. Volume Solid But what would you do to know how much space is occupied by an irregular object like a rock??

  42. Volume Displacement A solid displaces an equivalent volume of water. 50 mL 35 mL

  43. Volume Displacement So this object occupies:End volume – Start volume 50 mL – 35 mL = 15mL or 15 cm3

  44. DERIVED UNITS • FORCE: a push or a pull affecting the motion of an object 2nd Newton’s Law of Motion F = M x A; kg x m/s^2 referred to as Newton (N)

  45. WEIGHT • It is a FORCE. • The force exerted by gravity on any object. • While Mass does NOT vary with location, WEIGHT varies depending on the gravitational pull. • Where do you weigh the most? On the moon, or on Earth????

  46. DERIVED UNITS 4. DENSITY: how tightly the matter of an object is packed into a given volume  It is an important physical property Which one weighs more,1 kg of feather or 1 kg of nails??? Which one is less dense?

  47. The mass is the same -1 kg- , but their volumes -the space that they occupy- are different. The feathers occupy more space, so they are less dense

  48. DERIVED UNITS DENSITY Formula = Mass divided by VolumeExample: if the mass of your book is given in grams and its volume in cubic cm, what will the unit be for its density??

  49. Mass = 300 g Volume = 60 cm3 DENSITY = 300 grams 60 cubic centimeter = 5 g/cm3 Science Divide numbers to get the numerical value Divide units to get the final derived unit

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