Transcript Unit 2 Lesson 2

Unit 2 Lesson 2 Scientific Tools and Measurement
Unit 2 Lesson 2 Scientific Tools and Measurement
For Good Measure
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
What are the SI units?
• Second is the unit for time. Time is measured
using a stopwatch.
• Kelvin is the unit for temperature. Temperature is
measured using a thermometer.
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Unit 2 Lesson 2 Scientific Tools and Measurement
What are the SI units?
• 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).
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Unit 2 Lesson 2 Scientific Tools and Measurement
What are the SI units?
• 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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
How can we make very large or small
measurements easy to work with?
• 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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
How can we make very large or small
measurements easy to work with?
• 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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
Why are accuracy and precision
important?
• 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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
Why are accuracy and precision
important?
• How do these diagrams represent accuracy and
precision?
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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Unit 2 Lesson 2 Scientific Tools and Measurement
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.
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