Measurement

The International System (S.I.) is a set of standard unit of measurement for scientists throughout the world. Quantity Unit ABBREV Length meter m Mass kilogram kg Temperature kelvin K Timeseconds s Volumecubic meter m 3 S.I. Base Units

S.I. prefixes are added to the base units to increase or decrease their value by powers of 10. Numerical prefix SymbolMeaningMultiplierExponential Multiplier kilo kthousand1,0001 X 10 3 deci dtenth0.11 X centi c hundredth X milli m thousandth X 10 -3

Converting within a specific quantity requires moving the decimal place. Example: 546 µm = m Example: kL = 560 ml Example: 1000 g = 1 kg

The Metric Number Line We are mostly interested in measurements from the kilo to milli – region of the number line. Use a device to help you remember the order of the prefixes. Kind Hearted Dads Make Dark Chocolate Milk

Length is the distance covered by an object. Unit of measure for length is the meter (m). The instrument used to measure length is a ruler, meter stick, etc.

Mass is a measure of the quantity of matter in an object. Mass does not change with location. The unit used for mass is the gram (g). The instrument we use to measure mass is a balance.

Weight is a measure of the force of gravity between objects. Weight will vary with location and the unit of measure for weight is the Newton (N). The instrument we use to measure weight is the spring scale.

Temperature is a measure of the average kinetic energy of the particles in a sample of matter. We usually measure in Celsius ( 0 C) then change to Kelvin (K) when needed. The instrument used to measure temperature is the thermometer.

Kinetic energy is the energy an object has due to its motion. Gas molecules move faster than the molecules in solids and liquids, and therefore, have more kinetic energy. Gas moleculesLiquid moleculesSolid Molecules

Heat is the energy transferred as a result of a temperature difference. Left undisturbed, energy will flow from objects of high temperature to objects of low temperature until the objects have equal temperature. Unit – Joules (J) or Calories (cal) 1 cal – J 1000 cal = 1 kcal also called 1 food Calorie

A calorimeter is the Instrument used to measure energy.

Volume is the amount of space occupied by an object. SI is m 3 (too big!) = length X width X height 1 dm 3 = 1 L 1 cm 3 = 1 mL 1000 mL or cm 3 = 1 L or dm 3 The instrument we use most often to measure volume is the graduated cylinder.

Accuracy is how close a measurement is to the actual(accepted) value. Example: Your watch is accurate if it is close to that kept by the National Institute of Standards and Technology (N.I.S.T.) Error: Experimental error-difference Between yours & actual value Percent error = Experimental error x 100 Actual value Example: on board

Precision is how close a set of measurements are to each other. (repeatability) Example: A field goal kicker is precise if he kicks the ball through the goal posts every time.

Significant Figures or Digits The number of reliable digits in a measurement based on accuracy of the measuring instrument. The last digit in the number may be an estimated one.