Units and Measurements Mr. Stripling Pre-AP Chemistry Room 402

SI – used by all countries Based on 10 Base unit is the starting point Length, volume, mass, temperature Also others such as: area, energy, etc.

King Henry Died Unexpectedly Drinking Chocolate Milk

Length/ Distance https://www.youtube.com/watch?v=djTNUp4XIRo Measured in ___________ (base unit) You are going to be measuring some items around the room. Make a table to record the measurements Width of lab table Outlet Faucet Height of table (in class area) Length of table (in class area) Make sure to record your measurements in centimeters

Length/Distance Person is more commonly measured in ___________ Distance between towns or cities would be in ________________ A sheet of paper would be measured in _________ A grain of rice would be measured in ________

Mass Create a table to record your findings Measured in ____________ (base units) Tissue Box Calculator Safety glasses You are going to measure the mass of : Piece of paper Pen Notebook Paperclip Graduated Cylinder Penny Graduated Cylinder with 2mL of water Create a table to record your findings Graduated Cylinder with 5mL of water Graduated Cylinder with 10mL of water

Volume Base unit _______________ cm3 (cc) and mL 1 mL = 1 cm3 Calculated with measuring or water displacement Volume = height x width x length

Volume Water displacement Have to measure before and after, find the difference Not always convenient to measure this way

Volume Calculate the volume of the following: Chemistry book Two boxes Tissue box Lab table tops (front of room) Paper clip Calculator (or cell phone) Pencil Thumb tack Marble

Initial Volume Ending Volume Calculated Volume Paper clip Thumb tack Pencil Record calculations in cm3

Volume Liquid medicine is most conveniently measured in __________ Bottled soda or water is measured in __________ Water in a swimming pool would be measured in _____

Temperature Base unit – Kelvin (K) We are used to Fahrenheit or Celsius We can convert from one to the other: F to C (oF – 32) x 5/9= oC C to F (oC x 9/5) + 32 = oF C to K oC + 273 = K K to C K – 273 = oC

Temperature 100 oF = ______ oC 22oC = _____ oF 50 oC = _______ K 325 K = ________ oC How can you convert from Fahrenheit to Kelvin?

Graphs Display data Determines patterns Circle graphs show parts of a whole Divided into wedges that look like a pie (pie chart) Wedges equal 100%

Graphs Bar graphs show quantities of categories Quantity measured on the y-axis Independent variable on x-axis

Graphs Most graphs used in chemistry are line graphs Points on line graph show intersection of data of two variables Independent variables are plotted on x-axis Dependent are on the y-axis Independent variables are those deliberately changed in an experiment If line is straight (linear), slope can be calculated Slope = rise / run = y2-y1 / x2-x1

Graphs

Graphs

Graphs Take the data that you collected from the mass, length, and volume labs and create graphs that you believe would best display your data. Create a separate graph for each of the labs.

Dimensional Analysis Used to convert from one unit to another. Shows a relationship We will set it up as a fraction (bridge) The top has the unit we want to get in to The bottom has the unit we want to change out of

Review Prefixes Base units Convenient units are not always the base – examples Keys to converting – always use the base unit in the conversion Conversion factor **Know which unit goes on top and which goes on bottom The conversion factor shows a relationship between the 2 units used in converting

Dimensional Analysis Converting English to Metric using dimensional analysis Here are the relationships: 1 inch = 2.5 cm 1 ounce = 28 grams 16 ounces = 1 pound 1 cup = 0.24 liters

Scientific Notation Used to express large and small numbers that would have lots of zeros X.X x 10x

Scientific Notation

Scientific Notation

Scientific Notation

Significant Figures Nonzero numbers are always significant Ex: 72.3 has three All final zeros to the right of the decimal are significant Ex: 6.20 has three Any zero between significant figures is significant Ex: 60.5 has three Placeholder zeros are not significant. Remove placeholder zeros by rewriting the number in significant figures Ex: 0.0253 and 4320 each have three

Density Density – a physical property of matter and is defined as the amount of mass per unit volume. Common units of density for solids: Grams per cubic centimeter (g/cm3) Common units of density for liquids and gasses: Grams per milliliter (g/mL)

Density Usually cannot be measured directly Density equation: Density = mass / volume

Density Classwork On page 62 do problems: 65 (list, don’t draw),66, 67, 68 On page 64 do problems: 103 & 105 On page 977 do problems: 1 & 2 Show your work or receive no credit

Uncertainty in Data Accuracy – how close a measured value is to an accepted value Precision – how close a series of measurements are to one another

Error The difference between an experimental value and an accepted value. Calculating error: Error = experimental value – accepted value

Error Percent error expresses error as a percentage of the accepted value. Percent error = (IerrorI / accepted value) x 100 Important way of showing the precision of our calculations

Error Classwork On page 49 do problems: 32, 33, 34 Show your work or receive no credit

Classwork Do page 41 practice problem 11 and 12 (total of 12 problems) – express in scientific notation Do page 51 practice problems 35 and 36

Classwork Do the following problems:- #13 (a-d) on page 42 #99 (a-f) and #100 (a-f) on page 64