Measurements, Density, Moles Study Guide Unit 3

Question 1

Density

Answer 1

A ratio that compares the mass of an object to its volume

Question 2

Mole

Answer 2

Si base used to measure the amount of a substance, one mole contains 6.02 x 10^23 of representative particles in one mole

Question 3

Avogadro’s number

Answer 3

The number of representative particles in a mole 6.02 x 10^23

Question 4

Standard Temperature and pressure

Answer 4

STP

Question 5

Meniscus

Answer 5

The upward or downward curve of the surface of a liquid

Question 6

Accuracy

Answer 6

Refers to how close a measured value is to an accepted value

Question 7

Precision

Answer 7

Refers to how close a series of measurements are to one another precise measurements show little variation over a series of trials but may not be accurate

Question 8

Percent Composition

Answer 8

The percent by mass of each element in a compound

Question 9

Empirical Formula

Answer 9

A formula that shows the smallest whole number mole ratio of the elements of a compound and may or may not be the same as the actual molecular formula

Question 10

Molecular Formula

Answer 10

A formula that specifies the actual number of atoms of each element in one molecule or formula unit of the substance

Question 11

Significant figures when adding or subtracting

Answer 11

Round to the smaller number of DECIMAL PLACES

Ex. 4.065 + 118.20 = 122.265 which then becomes 122.27

Question 12

Significant figures when multiplying or dividing

Answer 12

Round to the smallest number of SIGNIFICANT FIGURES

Ex. 35.45 x 6.02 x10^23 = 2.134 x 10^25 which becomes 2.13 x 10^25

Question 13

Difference between accuracy and precision

Answer 13

Accuracy is many points that are near the real value whereas precision is all points together but not in the correct spot.