Chemisty - Chapter 3: Scientific Measurement

How do you write numbers in scientific notation?

The coefficient is always a number greater than or equal to one or less than ten, and the exponent is an integer

How do you evaluate accuracy and precision?

To evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To measure precision, you must compare the values of two or more repeated measurements

Why must measurement be reported to the correct number of significant figures?

Calculated answers often depend on the number of significant figures in the values used in calculations

measurement

a quantity that has both a number and a unit

scientific notation

a given number is written as the product of a coefficient and 10 raised to a power

accuracy

a measurement of how close a series of measurements comes to the actual or true value of whatever is measured

precision

a measure of how close a series of measurements are to one another

accepted value

the correct value for the measurement based on reliable references

experimental value

the value measured in the lab

error

the difference between the accepted and experimental value

percent error

the absolute value of the error divided by the accepted value, multplied by 100

significant figures

all the digits in a measurement that are known plus a last digit that is estimated

What makes metric units easy to use?

All metric units are based in multiples of 10, which makes conversion easier

What temperature do scientists commonly use?

Celsius and Kelvin

What determines the density of a substance?

It is determined by the composition of a substance, not the size

International System of Units (SI)

a revised version of the metric system

meter (m)

the basic unit of length

liter (L)

most convenient unit of volume; the volume of a cube that is 10cm along each side (1cm³ = 1mL)

kilogram (kg)

the basic SI unit of mass

gram (G)

1/1000 of a kilogram

weight

a force that measures the pull on a given mass

energy

the capacity to do work or produce heat

joule (J)

the SI unit of energy

calorie (cal)

the quantity of heart that raises the temperature of 1g pure water by 1C

Celsius scale

sets the freezing point of water at 0 and the boiling point at 100

Kelvin Scale

freezing point is 273.15 and boiling point is 373.15

absolute zero

the zero point on the kelvin scale

density

the ratio of the mass of an object to its volume

volume

amount of space something takes up

mass

the amount of matter an object has

temperature

a measurement of how hot or cold an object is

dimensional analysis

a way to analyze and solve problems using the units or dimensions of the measurements

What happens when a measurement is multiplied by a conversion factor?

The numerical value is generally changed, but the actual size of the quantity measured is the same

What kinds of problems can you solve using dimensional analysis?

It can solve problems in which a measurement with one unit is changed to an equivalent measurement with another unit

conversion factor

a ratio of equivalent measurements