Ch 2

Question 1

Scientists make many kinds of measurements

Answer 1

• The determination of the dimensions, capacity, quantity or extent of something
• Length, Mass, Volume, Density

Question 2

All measurements have 2 parts

Answer 2

• A number

* A unit

Question 3

Measurements

Answer 3

• are made relative to a standard

* have uncertainty

Question 4

English System

Answer 4

• Common measurements

* Pints, quarts, gallons, miles, etc.

Question 5

Metric System

Answer 5

Units in the metric system consist of a base unit plus a prefix.

Question 6

Exact numbers

Answer 6

• Have no uncertainty associated with them

* They are known exactly because they are defined or counted

Question 7

Measured numbers

Answer 7

Have some uncertainty associated with them

Question 8

Accuracy

Answer 8

How closely a measurement comes to the true, accepted value

Question 9

Precision

Answer 9

How closely measurements of the same quantities come to each other

Question 10

Significant Figures

Answer 10

Are the digits in any measurement known with certainty, plus one digit that is uncertain.

Question 11

Measured numbers convey

Answer 11

• Magnitude
• Units
• Precision

Question 12

Because measurements are never exact, we must include

Answer 12

• The magnitude of the measurement and

* The uncertainty of the measurement

Question 13

Significant Figures (sig figs)

Answer 13

• The numbers known with certainty plus one extra (uncertain or estimated) digit
• In other words, all digits in a (correctly-made) measurement are significant

Question 14

Rules for Sig Figs

Answer 14

1. All non-zero numbers in a measurement are significant.
2. All zeros between sig figs are significant.
3. In a number less than 1, zeros used to fix the position of the decimal are not significant.
4. When a number has a decimal point, zeros to the right of the last nonzero digit are significant
5. When a number without a decimal point explicitly shown ends in one or more zeros, we consider these zeros not to be significant. If some of the zeros are significant, bar notation is used.

Question 15

Rounding off Numbers

Answer 15

The number of significant figures in measurements affects any calculations done with these measurements

Question 16

Sometimes, the calculator will show more (or fewer) significant digits than it should

Answer 16

• If the first digit to be deleted is 4 or less, simply drop it and all the following digits
• If the first digit to be deleted is 5 or greater, that digit and all that follow are dropped and the last retained digit is increased by one

Question 17

Adding Significant Zeros

Answer 17

Sometimes a calculated answer requires more significant digits. Then one or more zeros are added.

Question 18

When multiplying or dividing, use

Answer 18

• The same number of significant figures in your final answer as the measurement with the fewest significant figures.
• Rounding rules to obtain the correct number of significant figures.

Question 19

When adding or subtracting, use

Answer 19

• The same number of decimal places in your final answer as the measurement with the fewest decimal places (least precise measurement).
• Use rounding rules to adjust the number of digits in the answer.

Question 20

If you have both addition/subtraction and multiplication/division in a formula,

Answer 20

• carry out the operations in parenthesis first, and round according to the rules for that type of operation.
• complete the calculation by rounding according to the rules for the final type of operation.

Question 21

Scientific notation

Answer 21

Is used to write very large or very small numbers

Question 22

In scientific notation

Answer 22

All digits including zeros in the coefficient are significant

Question 23

Calculations in Scientific Notation

Answer 23

• The significant figures are those in the coefficient

* Usually, numbers in scientific notation will be multiplied or divided

Question 24

Conversion factors

Answer 24

A ratio that specifies how one unit of measurement is related to another

Question 25

Dimensional Analysis

Answer 25

A problem solving method in which the units (associated with numbers) are used as a guide in setting up the calculations.

Question 26

The Steps of Dimensional Analysis

Answer 26

1. Write the unit you have to start out with on the left hand side of the page 2. Write the units you want on the right hand side of the page 3. Look for a conversion factor that contains both the units you start with and the units you want in the end 4. Multiply the number on the left by the conversion factor with the units you want on the top and the units you start with on the bottom. 5. Make sure your units cancel out.

Question 27

What if you don’t have a conversion factor between the units you have and the units you want?

Answer 27

Try to create a chain of conversion factors from the units you have to units you want

Question 28

Density

Answer 28

A ratio of the mass of an object divided by its volume Density = Mass/Volume