MEASUREMENT AND PROBLEM SOLVING Chapter 3 & 4

Importance of Measurements 1. Fundamental to all sciences 2. In chemistry you use the International System of Measurements (SI units).

Qualitative vs. Quantitative Measurements Qualitative -- descriptive, nonnumeric Quantitative -- results in a definite form, usually as numbers and units.

Accuracy – How close a measurement comes to the actual or true value Accuracy – How close a measurement comes to the actual or true value? To evaluate the accuracy of a measurement, it must be compared with the correct value.

Precision -- A measure of how close a series of measurements are to one another. Depends on more than one measurement.

Units : All measurements depend on units Science uses the metric system. Each type of measurement has a base unit.

Volume (the amount of space occupied by matter) = liter Length (distance) = meter Volume (the amount of space occupied by matter) = liter Mass (weight) = gram

Prefixes are added to the base unit in order to measure in different amounts.

Common prefixes 4. deci ( d ) = 1 /10 Kilo ( K ) = 1000 5. centi ( c ) = 1 / 100 6. milli ( m ) = 1/ 1000 Kilo ( K ) = 1000 2. Hecta ( H ) = 100 3. Deka ( D ) = 10

Density – the relationship between an objects mass and its volume. Density = Mass / Volume (D = M / V) Example: D = ? If the mass of an object is 114 g and takes up a volume of 10.0 ml. D = 11.4 g/ml.

If the mass of an object stays the same, but the volume changes then the density will change. Typically as the volume gets smaller the density gets larger. Water is an exception to this.

Temperature – of an object determines the direction of heat transfer. - Heat moves from the object of higher temperature to the object of lower temperature.

Almost all substances expand with an increase in temperature (thermal expansion).

Scales Celsius -- uses two reference points to set it, the freezing point ( 0º C ) and the boiling point of water ( 100 º C ).

Kelvin – ( absolute scale ) the freezing point of water is 273 Kelvin – ( absolute scale ) the freezing point of water is 273.15 K and the boiling point is 373.15 K. -No degree sign is used. -The zero point is equal to –273.15 º C , and is called absolute zero.

Conversion Formulas: K = º C + 273.15 K = 20°C + 273.15 = 293.15K º C = K – 273.15 °C = 118K – 273.15 = -155.15°C