unit 2 lesson 2 scientific tools and measurement

Unit 2 Lesson 2 Scientific Tools and Measurement

For Good Measure

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What is measurement?

• The ability to describe an observation is important.

• A description is a statement that reports what has been observed.

• A measurement is a description that includes a number and a unit.



Why do we use standard units of measurement?

• Measurements were once based on body parts, such as arms and feet.

• This was not accurate because body parts vary in size from person to person.

• Using standard units makes it possible for a person in one place to work with the same quantity as someone kilometers away.



Why do we use standard units of measurement?

• Standard units allow scientists to repeat one another’s experiments.

• Experiments must be repeatable to determine if the results are valid.


What is the International System of Units?

• The modern metric system is called the International System of Units (SI).

• The SI units are the language for all scientific measurements.

• There are seven base units used to express the different quantities: length, mass, time, temperature, amount of substance, electric current, and light intensity.



What are the advantages of using the SI?

• SI measurements provide a common international language for scientists to use to share and compare observations and results.

• Changing from one unit to another is easier in SI than other systems because most SI units are based on the number 10.

• Conversions in non-SI systems, such as converting from feet to miles, are more complicated.



Made to Measure


What are the SI units?

• Length, mass, time, and temperature are the most commonly used quantities.

• Meter is the unit of length. Length is measured with a meterstick, ruler, or measuring tape.

• Kilogram is the unit for mass. Mass is measured with a balance.




• Second is the unit for time. Time is measured using a stopwatch.

• Kelvin is the unit for temperature. Temperature is measured using a thermometer.




• Some units are derived units. A derived unit is calculated from a base unit.

• Volume is the amount of space something occupies. The SI unit for volume is the cubic meter (m3). Volume is measured using graduated cylinders and beakers.

• Liquid volume is expressed in liters (L), which is not an SI unit. One milliliter (ml) is equal to one cubic centimeter (cm3).




• Weight is the measurement of the gravitational force on an object. The SI unit for weight is the newton (N).

• Weight is measured using a spring scale and depends on the object’s mass.

• Measurements such as density must be calculated. Density is calculated by dividing an object’s mass by its volume.


How can we make very large or small measurements easy to work with?

• A prefix is one or more letters or syllables added to the beginning of a word to change its meaning.

• SI uses prefixes to express an SI unit that is larger or smaller than the base unit.

• Kilo- means 1,000 times, so a kilogram is 1,000 grams.

• Milli- indicates 1/1,000 times, so a millimeter is 1/1,000 of a meter.




• Scientific notation is a short way of representing very large numbers or very small numbers.

• Numbers in scientific notation are written in the form a × 10b.

• The value of a is usually a number between 1 and 10.

• Locate the decimal point and move it to the left or right until it is immediately before or after the numeral that becomes a.




• The exponent b tells how many places the decimal point is moved.

• If the decimal moves to the left, b is positive. If the decimal moves to the right, b is negative.

• The speed of light is 300,000,000 m/s. In scientific notation, this converts to 3 × 108 m/s.



Why are accuracy and precision important?

• Accuracy is a description of how close a measurement is to the true value of the quantity being measured.

• The smaller the difference between the measurement and the true value, the more accurate the measurement is.




• Precision is the exactness of a measurement.

• A precise measurement is repeatable and reliable.

• If a high precision measurement is repeated, the number obtained will be the same or very nearly the same.




• How do these diagrams represent accuracy and precision?



Why do scientists sometimes estimate measurements?

• People make estimations when doing everyday tasks such as rearranging furniture.

• Scientists may estimate to see if the data they collected is reasonable.

• Scientists may also estimate to determine which tool is best suited for making the measurements they need.



Tools of the Trade


How are tools used in science?

• Scientists use different tools to perform experiments.

• Hot plates can be used to increase the temperature of a substance.

• Test tubes are common containers for holding samples of materials. Test-tube racks hold test tubes upright.



How are tools used in science?

• Pipettes can be used to transfer liquids.

• Lab journals or notebooks and pencils are tools that scientists use to record data and observations.

• A hand lens, compound microscope, or electron microscope can be used to magnify small objects.

• Digital cameras are also used to record images of objects and environments to observe at a later time.



How are computers and technology used by scientists?

• The use of science for practical purposes is called technology. New technology leads to new discoveries.

• Calculators and computers allow scientists to compute, display, analyze, record, and model data. They even help scientists to publish their findings.

• Probeware, which is a measuring tool linked to a computer, can be used to obtain and display the values of a quantity for long-term study.


unit 2 lesson 2 scientific tools and measurement

Documents

si units

unit of length

scientific tools

base units

derived units

standard units of measurement

si measurements

scientific measurements