Chemistry Review for Final 1: Measurement

Chemistry Review for Final

By William Lovering

Significant Figures Rules

To determine the number of significant figures in a number use the following 3 rules: 

1. Non-zero digits are always significant

2. Any  zeros between two significant digits are significant. Example: 201

2. A final zero or trailing zeros in the decimal portion ONLY are significant. Example: 0.500 or 0.632000 the zeros are significant 0.006  or 0.000968 the zeros are NOT significant.

Significant figures in addition and subtraction

For addition and subtraction use the following rules: Count the number of significant figures in the decimal portion ONLY of each number in the problemAdd or subtract in the normal fashionYour final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem.

​Calculations with Sig Figs

​Know your rules for adding/subtracting and multiplying/dividing!

Significant Figures in Multiplication and Division

For multiplication and division use the following rule: 

The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. (You are now looking at the entire number, not just the decimal portion)

*This means you have to be able to recognize significant figures in order to use this rule*      

Example: 5.26 has 3 significant figures; 6.1 has 2 significant figures

​Calculations with Sig Figs

​Know your rules for adding/subtracting and multiplying/dividing!

The correct way to measure a value...

• Measurements should always reflect the degree of accuracy that a device is capable of producing.

• If you know the value of the smallest division marked on a measurement device, any values read from that device MUST contain that level of precision plus one estimate.

• For example, if a ruler is marked into tenths of a centimeter then the recorded value of a measurement would be to the hundredth of a centimeter.

​Making Measurements w Sig Figs

​Be sure to read all of the digits (numbers) from the measuring device and then estimate one digit (number)!

Significant Figures and Measurement

Which numbers count?

​Percent Error Calculations

​The formula for calculating % error is on Reference Table T!

Scientific Notation is a shorthand method of writing incredibly large and incredibly small numbers

• The integer (often represented by M) must be between 1 and 10.

• If the power of 10 (often represented by n) is negative, the number is incredibly small. If it is positive, then it is incredibly large.

Addition and Subtraction Procedure

• First, each power of ten must match. Do this by moving the decimal point of one number, changing the power of ten so that the number's actual value does not change.

• Add or subtract the M values and keep the same power of ten.

• Write the answer in correct scientific notation (M x 10ⁿ where M is between 1 and 10).

Multiplication and Division Procedure

• Multiply or divide the M values.

• Multiply or divide the powers of ten (which means adding or subtracting the exponents.

• Write the answer in correct scientific notation (M x 10ⁿ where M is between 1 and 10).

Open Ended

Six students used the ruler in Model 1 to measure the length of a metal strip. Their measurements

are shown at the right. Were all of the students able to agree on a single value (1, 2, 3…)

for any digit (ones place, tenths place, etc.) in the measurement? If yes, which value and digit did

they agree on? (Click the picture if you need to see it more closely)

Open Ended

The students obtained an even better ruler, shown in Model 3.

Were the students able to agree on a single value for any of the digits in their measurements using the new ruler? If yes, what value(s) did they agree on in which digits?

Multiple Choice

Which metric unit is used to measure length?

• Meters

• Liters

• Grams

Multiple Choice

Which metric unit is used to measure mass?

• Meters

• Liters

• Grams

Multiple Choice

Which digits are significant?

10.512

• 10.512

• 10.512

• 10.512

• 10.512

Multiple Choice

Which digits are significant?

36000.

• 36000.

• 36000.

• 36000.

• 36000.

Multiple Choice

Select the answer reported to the correct number of significant digits.

520 - 92.1

• 430

• 428

• 427.9

• 42

Multiple Choice

What is the correct numerical setup to calculate the percent error for a measurement of 49.67 g if the accepted value is 50.00 g ?

• $$49.67\ g\ -\ 50.00\ g$$

• $$\left(\frac{49.67\ g\ -50.00\ g}{50.00\ g}\right)\$$

• $$\left(\frac{49.67\ g\ -50.00\ g}{50.00\ g}\right)\ x\ 100$$

Multiple Choice

What is the error if the measured value is 2.65 g/cm³ and the accepted value is 2.70 g/cm³ ?

• 0.5 g/cm³

• 0.05 g/cm³

• -0.5 g/cm³

• -0.05 g/cm³

Multiple Choice

What is the percent error if the measured value is 2.65 g/cm³ and the accepted value is 2.70 g/cm³ ?

• 1.85 %

• 5 %

• 1.89 %

• 0.05 %

• 0.0185 %

Multiple Choice

What is the mass (in grams) pictured on this triple beam balance?

• 37.3

• 37.30

• 7.3

• 37.300

Multiple Choice

What is the mass (in grams) pictured on this triple beam balance?

• 263.49

• 623.5

• 263.490

• 263.5

Multiple Choice

Which of the following would best represent the volume of the liquid in this graduated cylinder?

• 20.6

• 27.0

• 25.9

• 26

Multiple Select

This number has 5 significant figures

• 10000

• 0.00025

• 20200

• 0.021000

Multiple Choice

Express the following in scientific notation:
.000457

• 457 x 10⁶
• 457 x 10^-6
• 4.57 x10⁴
• 4.57 x 10^-4

Multiple Choice

Multiply:
(3.4 x 10⁵)(1.2 x 10^-3)

• 4.08 x 10^-8
• 4.8 x 10²
• 4.08 x 10²
• 4.08 x 10^-15

Multiple Choice

Solve:
(2.1×10​²​​) × (3.0×10​⁴)

• 5.1 x 10²
• 6.3 x 10⁶
• 5.1 x 10⁶
• 6.3 x 10⁸

Multiple Choice

Solve:
(9 x 10^-6) / (3 x 10^-3) 

• 27 x 10^-9
• 3 x 10^-3
• 3 x 10^-9
• 27 x 10^-3

Multiple Choice

(2.3 x 10²)+(4.1 x 10²)=

• 6.4 x 10⁴
• 6.4 x 10²
• 6.4 x 10⁰
• .64 x 10¹

Multiple Choice

64,600,000 cm = ____ km

• 646

• 64.6

• 6,460

• 6.46

• 64,600

Multiple Choice

425,000 mL = ___ L

• 425

• 42.5

• 4,250

• 4.25

• 42,500

Multiple Choice

How many kilograms of calcium are there in 173 pounds of calcium? (1 pound = 454 grams; 1 kg = 1000 g)

• 1.10 kg

• 78.5 kg

• 110 kg

• 78500 kg

Multiple Choice

Gas costs $3.05 a gallon, and your car travels at 27 miles for each gallon of gas. How far can you travel in your car with $95 in your pocket?

• 11 miles
• 840 miles
• 7800 miles
• 870 miles