Unit 2 Chemistry

What is exponential notation for Deci?

10^-1

Volume

A measure of the size of a body or region in three dimensional space.

Mass

A measurement of the amount of matter in an object.

Weight

A measurement of the gravitational pull on matter.

Quantity

A quantity is something that has magnitude size or amount.

Conversion Factor

A ratio derived from the equality between 2 different units that can be used to convert from one unit to another.

Formula for density?

Density=Mass/Volume

Dimensional Analysis

Dimensional Analysis is a mathematical technique that allows you to use units to solve problems including measurements.

Extensive property

Does depend on the amount of matter present

Intensive property

Does not depend on the amount of matter present

Measurement represents what?

Quantities

What type of error are you trying to minimize by preforming three trials and averaging the results?

Random

How does the concept of sig figs relate to uncertainty in measurement?

Sig figs are all the values that are shown on measuring devices as well as the last estimated digit that you determine by guessing. The more significant figures there are on the instrument, the more accurate the measurement will be, but there always has to be an educated guess number.

Significant figures

Significant figures in a measurement consist of all the digits known with certainty plus one final digit which is someone uncertain or is estimated.

Are zeros at the end of a number but to the left significant?

Sometimes

What is the Atlantic-Pacific rule?

Start counting at the first non zero digit. If a decimal is present start on the Pacific side. If a decimal is not present start on the Atlantic side.

Sig figs depend on what?

The calibration of the measuring tool.

Are zeros that are the end of a number and to the right of the decimal significant?

Yes (200.00, 5 Sig figs)

Accuracy

Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured.

When a decimal point is placed at the end of a number what does that mean?

All digits are significant

What do sig figs include?

All known numbers and one final estimation.

Random Error

An error in measurement caused by factors that vary from one measurement to another (Caused by person).

Systematic Error

An error in measurement caused by the instrument used to measure (Scale factor error, zero setting error)

Density is what kind of property?

An intensive physical property

Significant doesn't equal what?

Certain

What do units of measurement compare?

What is to be measured to a previously defined size.

Are zeros that appear between non zero digits significant?

Yes (4.07, 3 Sig figs)

What is the exponential notation for Centi?

10^-2

What is the exponential notation for milli?

10^-3

What is exponential notation for Micro?

10^-6

What is exponential notation for Nano?

10^-9

What is exponential notation for Deka

10^1

What is exponential notation for Hecto?

10^2

What is exponential notation for Kilo?

10^3

What is exponential notation for mega?

10^6

What is meant by the statement "the term significant does not mean certain"?

Just because something is measured as close to perfect as it can be, it does not mean it's certain or exact.

What are sig figs?

Known digits and estimated digits

What do sig figs apply to?

Measured quantities

As temp goes up most substances do what? What happens to volume? What happens to density?

Most substances expand so volume goes up and density goes down.

As temp goes down what happens to most substances? What happens to volume? What happens to density?

Most substances shrink so volume decreases and density goes down.

Are zeros appearing in front of all non zero digits significant?

No (0.095, 2 Sig figs)

If a zero has not been measured or estimated, but is just a place holder is it significant?

No (5.60, 2 sig figs)

Scientific Notation

Numbers written in the form M x 10^n where the factor M is a number greater than or equal to 1 but less than 10, and n is a whole number.

Rounding rules for sig figs?

Only look one digit to the right to determine which way to round.

Percent Error

Percentage error is calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value then multiplying by 100.

Precision

Precision refers to the closeness of a set of measurements of the same quantity made in the same way.

With sig figs, an answer can not be more precise than what?

The least precise measurement.

With multiplication and division what number of sig figs do you use?

The lowest number of sig figa

Density

The ratio of mass to volume, or mass divided by volume.

Why does some error or uncertainty always exist in a measurement?

The skill of the tool you're using could have limitations on precision. The conditions of measurement also affect the outcome. The skill of the measurer puts limits on the reliability of the results.

With addition and subtraction what sig dig do you go to?

The smallest place holder

Directly proportional

Two quantities are directly proportional to each other if dividing by one another gives a constant value.

Inversely proportional

Two quantities are inversely proportional to each other if their product is constant.