unit 2 lesson 2 scientific tools and measurement
TRANSCRIPT
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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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.
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
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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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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).
Unit 2 Lesson 2 Scientific Tools and Measurement
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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.
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
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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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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.
Unit 2 Lesson 2 Scientific Tools and Measurement
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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