Day 12 Chapter 2 Section 1 Lab Day 13 – Measurements Day 14 Quiz on Units and Measurements Day 15 – Lab Density Day 16 – Quiz Scientific Notation and Sig Figs

HCl + Na2S  NaCl + H2S Day 12 Reaction Introduction: Chemistry uses moles to count amounts of elements and compounds. Using moles is very similar to counting by a dozen. It is a number, an amount. Your periodic table has the amount in grams for 1 mole of that particulart substance . Use your period table to calculate the values Questions: What type of reaction is this? Count the number of moles of each element and Compound Calculate the molar mass of each element and compound.

Objectives: Be able to use and apply the standard units of measure to numbers. Apply derived units to numbers (Density, Molar Mass) Use the Density Formula to solve problems Utilize Converstion Factors to manipulate units Analize numbers and use Scientific Notation in relation to significant figures when solving problems Be able to determine the Percent Error of an experiment. (Precise and accurate)

Units of Measurement Why do we need a “standard unit of Measurement? Report Data that can be reproduced Base Units Time = Seconds (s) Length = meter (m) Mass = kilogram (kg) Volume = space occupied by an object Liter (L)

= Combination of base units Example: Density Derived Units = Combination of base units Example: Density Density = Mass Divided by Volume How would we write this? Use symbols. Now What are the units for the following? Mass = ? Grams or g Volume = ? mL or cm3

Derived Units Continued Now What are the units for the following? Mass = ? Grams or g Volume = ? mL or cm3 Now… Insert them into the formula! or

Density So… Density is the Ratio of Mass to Volume.

Water displacement Determining Volume Here is an odd shaped Object… How would you find the volume if you couldn’t take any measurements? Water displacement that’s how… What happens when you get into a bath tube that is filled to the top with water? That’s right it over flows! Why.. Water displacement

Water Displacement Let’s take our object And a graduated Cylinder filled with some water … enough to cover the object … but not completely filled (remember what happened to the bath tube!)

Water Displacement and Volume What would happen if we placed our object … into the graduated cylinder? The Water level starts at.. 46 mL Ends at 66 mL What’s the difference… 20 mL That’s the volume of the object

Using the Density formula answer the following questions. A piece of metal with a mass of 147g is placed in a 50mL graduated cylinder. The water level rises from 20mL to 41mL. What is the density of the metal? What is the volume of a sample that has a mass of 20g and a density of 4 g/mL?

Units All measurements start with the base unit Length is m or meters Volume is L or liters Mass is g or grams How ever… what if the object is less than the base unit? Let’s look at length or meters (m) 1 meter

Each part is 1/10th of a meter Each part is called a decimeter or dm Units continues Each unit (m, L, g) is broken down into parts of 10 Lets break this meter stick into 10 parts 1 meter 1 2 3 4 5 6 7 8 9 10 Each part is 1/10th of a meter Each part is called a decimeter or dm So… what is the length of this nail? 4 dm or 4 decimeters

This is 1 dm This is 1 cm This is 1 mm

Prefixes Used with SI Units Look at your chart on page26

Examples Centimeter = ? 100th of a meter or .01 or 10-2 Kilometer = ? – 1000 meters or 10 3 Millimeter 1000th of a meter / or .001 / or 10-3

Temperature What is the SI Unit of Temperature? Kelvin (K) 273 K = freezing point of water 373 K = boiling point of water What’s the difference between the two? 100 degrees What is Celsius? Temperature based on 0o – 100o C We will always convert Celsius to Kelvin, unless told not to.

Converting Kelvin to Celsius Convert - Celsius to Kelvin oC (what you measured) + 273 K = Kelvin Convert – Kelvin to Celsius oK (what you measured) – 273 K = oCelsius Convert the following to Kelvin 357o C -39o C Convert the following to Celsius 266 K 332 K

A Look Ahead Home work = Problem Set #7 Page 62 - #s 59, 61, 62, 64, 66, 67, 68 Lab Day 13 – Measurements Day 14 Quiz on Units and Measurements Day 15 – Lab Density Day 16 – Quiz Scientific Notation and Sig Figs

Day 14 Quiz Units and Measurements Chapter 2: Sec 2/3 Sig Figs Scientific Notation Rounding

Objectives: NEW... Analize numbers and use Scientific Notation in relation to significant figures when solving problems Be able to determine the Percent Error of an experiment. (Precise and accurate) REVIEW... Be able to use and apply the standard units of measure to numbers. Apply derived units to numbers (Density, Molar Mass) Use the Density Formula to solve problems Utilize Converstion Factors to manipulate units

Density Lab Materials; Formula: D=M/V Data Table: Cork stopper, Rubber stopper, Nut and bolt Graduated cylinder, water Formula: D=M/V Data Table: MASS VOLUME DENSITY Final (mL) Initial (mL) Volume Cork Stopper Rubber Stopper Nut & Bolt

Scientific Notation What's the goal of Scientific Notation? Condense the number that is written Example: What would you rather write 0.00000000000000000456 Or 4.56 x 10-18

Rules of Scientific Notation It’s all about the decimal point! And power of 10! Example: 645,000 1st… move the decimal point so one # is to the left of it 6.45000 2nd… place “x 10” to the right 6.45000 x 10 3rd… count the number of spaces you moved the decimal point. 6.45000 X 105 Almost Done!

6.45000 X 105 Now get rid of the zeros 6.45 X 105 Rules: #1..moving the decimal point to the left… the exponent gets bigger #2… moving the decimal point to the right… the exponent gets smaller 64.5 X 10… what's the exponent 6.45 X 104

Convert to Scientific Notation Pretest 134,000 5,400 0.001034 0.00078

Adding Exponents Rules: 1st… exponents need to be the same. Move the decimal point until the two numbers have the same exponent 2nd… add OR subtract the numbers… not the exponents. Example: Add the following #s…Follow the Rules 6.45 x 105 3.11 x 104 Answer: 6.76 x 105

Practice problems pg 32 Addition and Subtraction Every problem

Multiplying / Dividing Rules: 1st… multiply the numbers 2nd… add the exponents Dividing Rules 1st… divide the numbers 2nd… subtract the exponents

Practice Problems pg 33 Multiply (2 x 103) x (3 x 102) = Divide (9 x 108) ÷ (3 x 10-4) =

or Conversions 1000𝑚 1𝑘𝑚 1𝑘𝑚 1000𝑚 48𝑘𝑚 1 1000𝑚 1𝑘𝑚 48000 Rules: 1st… write down what you know 2nd… write down what you want to know 3rd… what conversion factor are you going to use to get there? Convert 48km to meters (factor: 1km=1000m) =__________m or 1000𝑚 1𝑘𝑚 1𝑘𝑚 1000𝑚 48𝑘𝑚 1 1000𝑚 1𝑘𝑚 48000

Types of Measurements Precise vs. Accurate

Percent Error The Accepted value is a known value Error = Accepted - Measured

% error example The accepted density for copper is 8.96g/mL. Calculate the percent error for each of these measurements. 8.86 g/mL 8.92 g/mL 9.00 g/mL 8.98 g/mL 1.11% .45% .45% .22%

Significant Figures or Sig Figs Tells the how precise the measurement is Example: Which is more precise? 3.5 or 3.52g

Rules for Sig Figs – pg. 39 Non-zero umbers are always significant Zeros between non-zero numbers are always significant All final zeros to the right of the decimal place are significant. Zeros that act as placeholders are NOT significant. Convert quantities to scientific notation to remove the placeholders. Counting numbers and defined constants have an infinite number of significant figures.

Another Set of rules 6 050 – don’t count 6 050. - count Find the left most non zero number. If there is a decimal point, all zeros to the right of that number, are significant. If there is not a decimal point, zeros don’t count! Sandwiched zeros are always significant! 6 050 – don’t count 6 050. - count 0.0006050 - count

Examples – use your rules Which numbers are significant? 72.3 60.5 6.20 0.0253 4320 125000 Help yourself out – convert to Scientific Notation

Rounding Numbers – pg 40 If the digit to the immediate right of the last sig fig is less than five, do not change the last sig fig. If the digit to the immediate right of the last sig fig is greater than five, round up the last sig fig If the digit to the immediate right of the last sig fig is equal to five and is followed by a nonzero digit, round up the last sig fig. If the digit to the immediate right of the last sig fig is equal to five and is not followed by a nonzero digit, look at the last sig fig. if it is an odd digit, round it up. If it is an even digit, do not round up

A Look Ahead Homework: Problems: Day 15: Lab – Density Day 16: Quiz – Sig figs, Scientific Notation