19 terms

# Scientific Measurement

#### Terms in this set (...)

accuracy
closeness of measured value to correct value
precision
closeness of measured value to other measured values
What is the conversion factor from km. to ft.? If Joe traveled 12 kilometers, how many feet did he travel? (Site 1)
1km/12km=3281ft/x
Why are leading zeros to the left of non-zero digits not significant? (Site 2)
Because there are placeholders.
Why is it so important for measurements in an experiment to be accurate AND precise?
It so important for measurements in an experiment to be accurate and precise because you need to get accurate and precisise results.

It is important that what you measure has meaning to what you are investigating...

If your measuring instrument always gives values that are closely grouped - precise - they will be of little value if the calibration of the equipment is such that the measured values are not correct - accurate...

Similarly, if the equipment is calibrated correctly but your measurements vary wildly you will not know which measurement, if any, is correct...

This second case can come about by using a very accurate AND precise instrument but not using the sensor correctly...
Find the mass of the cone using the triple beam balance.
543.0 g
Scientists use significant figures in order to provide precise measurements in recorded data.

Which measurement would not be possible to obtain from the triple beam balance shown?
...
What is the mass of the light bulb?
...
What is the mass of the light bulb and paperclips together?
251.0 g
A number should be rounded up if _______.
the number after it is between 5 and 9
How many significant figures are in the measurement 0.020 km?
2
Which of the following is not one of the three principles from which the metric system is based?
Metric measurements cannot be converted to any other form of measurement.
When converting from kilometers to meters, the decimal is moved _______.
three places to the right
What is 0.25 kilometers expressed in centimeters?
25000 cm
Explain why significant figures represent the precision of a measurement and not its accuracy.
A measurement that has a larger number of significant figures has a greater reproducibility, or precision because it has a smaller source of error in the estimated digit. A value with a greater number of significant figures is not necessarily more accurate than a measured value with less significant figures, only more precise. For example, a measured value of 1.5422 m was obtained using a more precise measuring tool, while a value of 1.2 m was obtained using a less precise measuring tool. If the actual value of the measured object was 1.19 m, the measurement obtained from the less precise measuring tool would be more accurate.
What is the difference between accuracy and precision and which is most important to scientific measurement?
Accuracy describes the difference between the measurement and the part's actual value, while precision describes the variation you see when you measure the same part repeatedly with the same device.
Explain why scientists use the metric system for scientific measurements.
The metric system is used as part of the International System of Units, known as SI. Having an international system that all scientists use eliminates confusion and allows scientists around the world to understand each other's measurements. The metric system also allows for simple conversion from smaller to larger units or larger to smaller units.
What are the basic prefixes used in the metric system and how do they relate to the size of the base unit?
The basic prefixes are kilo, hecto, deka, milli, centi, and deci. The kilometer is 1000 times larger than the base unit, the meter. The hecto is 100 times larger and the deka is 10 times larger than the base unit. The millimeter is 1000 times smaller than the base unit, the meter. The centi is 100 times smaller and the deci is 10 times smaller.
How do the prefixes in the metric system relate to the basic units?
The prefixes in the metric system are used to modify the basic units. The prefixes either make the unit a larger measurement, as in the case of meter to kilometer, or they make the unit a smaller measurement, as in the case of meter to millimeter.