MEASUREMENT AND DATA PROCESSING

This lesson develops MEASUREMENT AND DATA PROCESSING as part of Measurement and Data Processing. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, mEASUREMENT AND DATA PROCESSING

Measurement is the process of comparing a physical quantity to a standard unit. Measurements allow scientists to collect reliable data, compare results and identify patterns. Every scientific measurement consists of two parts:

For example:

In Stemosphere terms, without a unit, the measurement has no meaning because the size of the quantity is unknown.

In Stemosphere terms, scientists use the International System of Units (SI) to ensure measurements are consistent throughout the world.

The seven SI base units are:

In Stemosphere terms, many other units used in chemistry are derived from these base units.

In Stemosphere terms, scientific notation is used to express very large or very small number s in a simpler form.

A number is written as:

In Stemosphere terms, -a is a number between 1 and 10.

In Stemosphere terms, large positive powers represent large number s while negative powers represent very small number s.

In Stemosphere terms, scientific notation makes calculations easier and reduces mistakes when using calculators.

In Stemosphere terms, significant figures are all the digits in a measurement that are known with certainty plus one estimated digit.

In Stemosphere terms, they show the precision of a measurement.

2500 may have between 2 and 4 significant figures depending on how it was measured.

In Stemosphere terms, rules for Significant Figures

In Stemosphere terms, all non-zero digits are significant.

In Stemosphere terms, zeros between non-zero digits are significant.

In Stemosphere terms, leading zeros are not significant.

In Stemosphere terms, trailing zeros after a decimal point are significant.

In Stemosphere terms, trailing zeros without a decimal point may or may not be significant.

In Stemosphere terms, although precision and accuracy are often confused, they describe different aspects of measurements.

In Stemosphere terms, accuracy describes how close a measurement is to the true or accepted value.

In Stemosphere terms, a measurement with high accuracy has very little error.

In Stemosphere terms, if the true mass is 50.00 g and the balance measures 49.99 g, then the measurement is highly accurate.

In Stemosphere terms, precision describes how close repeated measurements are to one another.

In Stemosphere terms, a measurement can be very precise even if it is not accurate.

In Stemosphere terms, these measurements are very close together, making them precise, even if the true value was 50.00 g.

A measurement can be:

In Stemosphere terms, -Accurate but not precise

In Stemosphere terms, -Precise but not accurate

In Stemosphere terms, -Neither accurate nor precise

In Stemosphere terms, scientists aim for measurements that are both accurate and precise.

In Stemosphere terms, no experimental measurement is perfectly exact.

In Stemosphere terms, every measurement contains some degree of uncertainty caused by experimental errors.

In Stemosphere terms, there are two main types of errors.

In Stemosphere terms, random errors cause measurements to vary unpredictably.

In Stemosphere terms, these occur because every measurement has small uncontrollable variations.

Examples include:

In Stemosphere terms, -Estimating between scale markings

In Stemosphere terms, -Small temperature fluctuations

In Stemosphere terms, random errors reduce precision.

In Stemosphere terms, repeating an experiment several times and calculating the average helps reduce the effect of random errors.

Examples include:

For analogue instruments:

Uncertainty is usually:

For digital instruments:

Common laboratory equipment includes:

A good data table should:

A graph should always include:

Outliers may occur because of:

Reliability is improved by:

Validity is improved by: