Chem 211 Week 1 notes
Chem 211 Week 1 notes CHEM 211-003
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This 6 page Class Notes was uploaded by Neha simon on Friday September 2, 2016. The Class Notes belongs to CHEM 211-003 at George Mason University taught by Pritha G. Roy in Fall 2016. Since its upload, it has received 61 views. For similar materials see General Chemistry 1 in Science at George Mason University.
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Date Created: 09/02/16
31/08/16 W1D2 Chap 1 Notes units Chemistry uses SI units: units used in Chemistry Common prefixes: These units can be converted into Tens. 31/08/16 W1D2 The sides of this cube are 1m what is the volume? 1*1*1=1 must have units m*m*m= m^3 NB: when computing numbers you have to compute the measurements as well. Convert into centimeters cubed. 1 m= 100cm 100*100*100= 1,000,000,000 cm* cm* cm= cm^3 Conversion factors: conversion factors are ratios used to express a quantity in different units. - Conversion factor is used to cancel out units. Have to have a systematic approach - State problem - Plan - Clarify the known and the unknown - Suggest steps from the known and the unknown. - Make a flow chart. - Solution - Check - Comment - Followup problem Density Density= mass/volume Mass= density * Volume Volume= Mass/density Density= mass/volume Kg/m^3> have to write is as kg/m^3 1000mL= 1L =1000 cc 31/08/16 W1D2 Temperature scales: Kelvin: this is called the absolute scale and here is why > The size of Kelvin is 100 > K Scale has a different Zero point, an absolute zero. > Absolute 0K= 273.15 ºC > Hence the boiling point and the freezing point are + or 273.15 K Ex: A child has a fever of 311.15 K what is the degree in Celsius? 311.15 ANS: 38 ºC 273.15 38.00 Celsius: based on the freezing and boiling point of water > The size of Celsius is 1/100 between freezing and boiling point. Fahrenheit: freezing point is 32 ºF and boiling point is 212 ºF > 212 – 32= 180 Fahrenheit degrees represents the same change as 100 Celsius degrees > 1 Celsius degree = 180/100 Fahrenheit degrees = 9/5 Fahrenheit. Conversion from ºC to ºF: change the degree size and adjust the zero point. ºF= 9/5 * (ºC) + 32 Conversion from ºF to ºC: Change the zero point then adjust the degree size ºC= (ºF – 32) 5/9 * This is just solving for ºC A child has a fever of 38.7 ºC normal body temperature is 98.6 ºF does this child have a fever? What is the temperature in kelvins? ºF= 9/5 (38.7 ºC) + 32 K= 38.7 + 273.15 ºF= 101.7 K = 311.8 Yes the child has fever 31/08/16 W1D2 Sig figs Every measurement has uncertainty; the rightmost digit is always estimated. The recorded digit is always is sig figs The greater the # of digits the greater the certainty. Anything NON ZERO is significant Zeros are significant after the decimal point. Zeros are significant between numbers. Zeros that end a number are significant. Whether they occur before or after the decimal point. DECIMAL POINT MUST BE PRESENT. 31/08/16 W1D2 IF your number starts with a decimal point add a 0 before the point . Rules for sig fig calculation 1. for multiplication and division: the ans contains the same number 2. for + and : the least number of sig figs will be the ruling one for the answer. Ex: 30.5 +10.358 40.858 ANS: 40.9 if you have to round based on 5 than odd numbers round up and even numbers stay the same. Keep everything till you get to the final step. Precision and accuracy and error - Systematic error: produces values that are either all high or all low - Random error: produces values that are both high and low. 31/08/16 W1D2
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