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# Chemistry Test 3-1

### measurements

Question | Answer |
---|---|

something that has magnitude, size, or amount | quantity |

size of a quantity determined by a measurement process and described by both a number and a unit | magnitude |

compare what is to be measured with a previously defined size | units of measurement |

the choice of unit depends on | the quantity being measured |

single measurement system agreed on by scientists all over the world | SI system |

some non-SI units are still used by __ | chemists |

objects or natural phenomena that are of constant value, easy to preserve, easy to reproduce and practical in size | standards of measurement |

standards are used to __ | compare |

basic quantities measured in arbitrary units established by international agreement | fundamental quantites |

used in measuring fundamental quantities | SI base units |

the distance between 2 points OR the path traveled by light in a vacuum during a time interval | length |

the amount of matter in a body | mass |

duration of an event OR vibrations of Cesium 133 | time |

degree of hotness or coldness of an object | temperature |

amount of substance | mole |

combinations of fundamental quantites so that combinations of units are produced | derived units |

how do you convert from C to Kelvin? | add 273 to the C |

used to figure out the # of atoms or molecules in a given amount of substance | mole |

number of units or fraction of a unit each line on the scale stands for | calibration |

what is the percent error formula/ | %E= Value a- Value e/Value a |

since most objects___ expand as the temperature increases, the volume ___ | expand; increases |

as volume ___ density ___ | increases; decreases |

good measurements are both ___ and ___ | accurate and precise |

refers to the closeness of measurements to the correct or accepted value of the quantity measured | accuracy |

what does accuracy depend upon? | 1. how carefully the measurement is done 2. quality of the instrument (in working order/well made) 3. one measruement or the average of one measurement as compared to the accepted value |

what is accuracy determined by? | percent error |

value accepted comes from ___ | books or tables |

value experimental comes from | the experiment or measurement in lab |

the numerator of the percent error formula is called ____ | absolute error |

refers to the closeness of a set of the same quantity made in the same way | precision |

what does precison depend upon? | 1. skillful estimation (your guess) 2. number of divisions in the instrument (calibration) 3. how close several measurements are to each other. |

one way to look at precison | standard deviation |