Download 1 - contentextra

Worksheet 11.1
Chapter 11: Measurement and data processing – glossary
Accuracy The accuracy of a result is a measure of how close it is to some accepted or literature
value. If an experiment is accurate then the systematic error is small.
Best-fit line The best-fit or regression line aims to display a relationship which may not be apparent
due to experimental errors. The best-fit line averages out the errors with half the data points on each
side of the line.
Density
Density (ρ) is defined as mass(m) per unit volume(V): ρ = m/V.
Dependent variable Dependent variable (also known as the responding or measured variable) is the
variable that is measures as the experiment proceeds.
Enthalpy The amount of heat energy possessed by a chemical system. It is stored in the chemical
bonds as potential energy. When substances react, the difference in the enthalpy between the reactants
and products (at constant pressure) can be measured.
Gradient
The gradient of a straight line = increase in y coordinate/increase in x coordinate.
Ideal gas equation The equation relating the absolute temperature (T) in K, pressure (P), volume (V)
and amount (n) of an ideal gas. PV = nRT.
Independent variable The variable that you manipulate and for which you set the values.
Outlier An outlier is a data point which does not fit the general trend. When it is the result of an
experimental error its presence distorts the interpretation of the data. Outliers should not be removed
without justification, however, as they could be genuine results.
Percentage error Percentage error = ((accepted value – experimental value)/ accepted value)
 100%.
Percentage uncertainties
Percentage uncertainty = (absolute uncertainty /measured value)  100%.
Polynomial A polynomial is a mathematical expression involving a sum of powers in one or more
variables multiplied by coefficients. A polynomial in one variable has the following form: y = anxn
+…+ a2x2 + a1x + a0.
Precision
Precise measurements have small random errors and are reproducible in repeated trials.
Random errors Random errors make a measurement less precise, but not in any particular direction.
They are expressed as an uncertainty range, such as 25.0 ± 0.1 cm3.
Reliability
reliable.
The opposite of uncertainty. If the uncertainty is great, the measurement is not very
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com
1
Repeatability
results.
Experiments are repeatable if the same person duplicates the experiment with the same
Reproducibility
Experiments are reproducible if several experimentalists duplicate the results.
Significant figures The number of significant figures in a measurement is the number of digits that
are known for certain plus the first uncertain one.
Systematic errors
Systematic errors occur when there is an error in the experimental procedure.
Tangent A tangent to a given curve is a line that passes through a point on the curve and has the
same gradient as the curve at that point.
Uncertainty An estimate of the range of values within which the true value of a measurement is
expected to be. It is normally expressed as a range of values, such as 27.0 ± 0.2 oC.
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com
2