The Importance of Measurement Chapter 3

Qualitative Measurement Types of Measurements Qualitative Measurement Measurement that gives results in a descriptive, nonnumerical form. “This person feels hot, it might have a fever.” Quantitative Measurement Measurement that gives results in a definite form, using numbers and units. “This person’s temperature is 39.2 0C.”

Uncertainty in Measurements Difference between Accuracy, Precision and Error. Accuracy It is a measure of how close a series of measurements comes to the actual (true) value. Precision It is a measure of how close a series of measurements are to one another. Error It is the difference between the accepted value and the experimental value.

Good Accuracy and Good Precision

Poor Accuracy, Good Precision

Poor Accuracy, Poor Precision

Error and Percent Error Error Error = Exp. Value – Accept.Value Percent Error Exp. Value – Accept Value % Error = x100 Accept Value

Temperature Temperature It determines the direction of heat transfer. It measures the average kinetic energy of particles in matter. Almost all substances expand with an increase of temperature and contract as the temperature decreases. Water is an exception.

Temperature Scales There are three temperature scales Celsius Scale: Based on the freezing and boiling point of water at standard pressure (sea level) Freezing point of water = 0 0C Boiling point of water = 100 0C

Temperature Scales Kelvin Scale: This scale reflects the relationship between temperature and kinetic energy. There are no negative temperatures Zero point in the Kelvin scale is also known as the absolute zero. Particles of matter at this temperature have no kinetic energy.

Conversions between 0C and Kelvin To convert from 0C to Kelvin K = 0C + 273 To convert from Kelvin to 0C 0C = K – 273

Temperature Conversions Convert - 40 0C into Kelvin. Convert 300 K into 0C.

Temperature Conversions Fahrenheit to Celsius 0C = (0F -32)/ 1.8 Celsius to Fahrenheit 0F = (1.8 x 0C) + 32