1. 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

2. 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.

3. 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)

4. 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)

5. = 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

6. 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

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

8. 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

9. 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!)

10. 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

11. 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?

12. 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

13. 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

14. This is 1 dm
This is 1 cm
This is 1 mm

15. Prefixes Used with SI Units
Look at your chart on page26

16. 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

17. 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.

18. Converting Kelvin to Celsius
Convert - Celsius to Kelvin
oC (what you measured) 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

19. 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

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

21. 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

22. 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

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

24. 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
2nd… place “x 10” to the right
x 10
3rd… count the number of spaces you moved the decimal point.
X 105
Almost Done!

25. 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

26. Convert to Scientific Notation
Pretest
134,000
5,400

27. 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 x 104 Answer: 6.76 x 105

28. Practice problems pg 32
Addition and Subtraction
Every problem

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

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

31. 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

32. Types of Measurements
Precise vs. Accurate

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

34. % 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%

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

36. 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.

37. 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
count
count

38. 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

39. 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

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