Measurements and Unit Conversions in Science

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Questions and Answers

What is the smallest graduation of measurement for an instrument referred to as?

Accuracy

Rounding

Error

Precision (correct)

When providing an error for a measurement, what should you assume if no error is given?

The error is always zero.

The error must be provided based on previous studies.

The error is +/- 1/2 the measurement of the next decimal place. (correct)

The error is equal to the measured value.

What should you do if the error is greater than the precision of the measuring instrument?

Round the error to the nearest whole number.

Ignore the measurement.

Provide the error based on human measurement. (correct)

Use the instrument's precision for the error.

Which rule applies when rounding a calculation with measured numbers?

Round your answer to the precision of the least precise starting measurement. Signup and view all the answers

In unit conversion, what is the first step to transform your measurement?

Turn the original number into a fraction over 1. Signup and view all the answers

What is the purpose of multiplying by a conversion factor in unit conversion?

To eliminate the original unit. Signup and view all the answers

If you measure a temperature of 22.5°C and estimate the error at +/- 0.1°C, what should you consider about the precision of your instrument?

The precision must be less than +/- 0.1°C. Signup and view all the answers

What is the rule when rounding measurements that share the same unit?

Round to the precision of the least precise measurement. Signup and view all the answers

What is the isobath interval?

The difference in depth between one isobath and the next Signup and view all the answers

What is the purpose of an index isobath?

To provide a visual guide by using darker, thicker lines for easier identification Signup and view all the answers

How do isobaths behave near steep slopes?

They become closer together Signup and view all the answers

What happens to isobaths in a valley or canyon?

They bend and point upslope Signup and view all the answers

In a chart with a 100 ft isobath interval, where would you find an index isobath?

Every 500 ft Signup and view all the answers

Why should depths between isobaths not be interpolated?

They may not represent true depth variations. Signup and view all the answers

What dictates the isobath interval used on a map?

The scale of the map and the steepness of the terrain Signup and view all the answers

Which type of rock forms from existing sediments?

Sedimentary rock Signup and view all the answers

What is the primary process that leads to the formation of sedimentary rocks?

Precipitation of minerals from water Signup and view all the answers

Which of the following textures is associated with intrusive igneous rocks?

Phaneritic Signup and view all the answers

Which type of sediment is derived from pre-existing terrestrial rocks?

Lithogenous Signup and view all the answers

What defines the composition of igneous rocks?

Felsic, mafic, and ultramafic minerals Signup and view all the answers

Which sedimentary rock is characterized by the presence of fossils?

Coquina Signup and view all the answers

What is the primary characteristic of extrusive igneous rocks?

Formed at the Earth's surface and cool quickly Signup and view all the answers

Which rock is classified as an evaporite?

Gypsum Signup and view all the answers

What is a common feature of gravel-sized sediments?

Typically found in high-energy water environments Signup and view all the answers

What does the Prime Meridian represent in the world coordinate system?

The Y-axis intersecting Greenwich, England Signup and view all the answers

Which feature is formed at convergent plate boundaries?

Deep ocean trenches or mountain ranges Signup and view all the answers

What typically occurs at divergent boundaries?

Seafloor spreading and shallow earthquakes Signup and view all the answers

What is the function of isobaths on bathymetric charts?

To connect points of equal depth Signup and view all the answers

In which situation would you expect to find the most explosive volcanic eruptions?

At subduction zones Signup and view all the answers

How are transform boundaries characterized?

By strong earthquakes and the absence of volcanic activity Signup and view all the answers

What coordinate format should be used to express latitude and longitude?

Degrees with indicators for N/S and W/E Signup and view all the answers

What geological activity is least expected at transform plate boundaries?

Volcanic eruptions Signup and view all the answers

What is the minimum error for salinity when recorded using a refractometer?

+/- 0.5 ‰ Signup and view all the answers

How should the result of 12.6 cm + 3 cm be rounded?

16 cm Signup and view all the answers

What is the angle measurement corresponding to due West?

270° Signup and view all the answers

What is the relationship between grams per milliliter (g/mL) and grams per cubic centimeter (g/cm³)?

They are equivalent. Signup and view all the answers

In the context of measuring angles, how is an angle always measured for oceanography?

From 0 to 360° clockwise from north Signup and view all the answers

What is the latitude of San Francisco?

38° North of the Equator Signup and view all the answers

To convert centimeters to inches, what factor needs to be applied?

2.54 cm = 1 in Signup and view all the answers

What is the maximum acceptable error for measuring angles with a protractor?

+/- 2° Signup and view all the answers

Study Notes

Error, Precision, and Rounding

All measurements have inherent error due to instrument precision.
Error is typically +/- 1/2 the value of the next decimal place of the measurement.
If error is greater than precision, provide an error based on human measurement, not exceeding the instrument’s precision.
For example, a thermometer reading 30.6°C with a precision to the tenths place should have an error of +/- 0.1°C or 0.2°C.

Unit Conversion

To convert units, create a fraction with the original number and multiply by a conversion factor, a fraction equal to 1.
Units you want to cancel out should be in the denominator, and units you want to keep should be in the numerator.
Example: 3605 cm to inches: 3605 cm x 1 in / 2.54 cm = 1419 in
Round answer to the same precision as the least precise measurement involved in the calculation.

Reading a Refractometer

Measures refractive index of liquids, providing density (g/mL) and salinity (ppt).
1 g/mL equals 1 g/cm³.
Read the line measurement on the device to determine density and salinity.
Salinity precision: 1 ppt, error: +/- 0.5 ppt
Density precision: 0.001 g/mL, error: +/- 0.0005 g/mL

Angles & Compasses

Circles contain 360° of arc, starting at 0° facing north (N).
Moving clockwise, East (E) is 90°, South (S) is 180°, West (W) is 270°, and back to North (N) is 360°.
Use a protractor for angle measurement.
Oceanographers measure angles from 0° to 360° clockwise from North.
Include an error of +/- 2°.

Latitude and Longitude

Angular coordinate system used for locating points on Earth’s surface.
Longitude measures angular distance away from the Prime Meridian (0° longitude), running north to south.
Latitude measures angular distance north or south of the Equator (0° latitude), running parallel to it.
Latitude/Longitude format: example: 24.6° N, 56.2° W +/- 0.2°.

Plate Boundaries

Edges of lithospheric plates, where earthquakes, volcanoes, and tsunamis occur.
Divergent boundaries (spreading centers): plates move apart, new seafloor forms, shallow earthquakes, volcanic seamounts, and lava flows.
Convergent boundaries: plates collide, either subducting or forming mountain ranges. Subduction zones have deep trenches and large earthquakes. Continental collisions create high mountains.
Transform boundaries: plates slide past each other, causing strong but less abundant earthquakes than convergent boundaries.

Bathymetric Maps and Isobaths

Bathymetric charts show ocean floor depth.
Isobaths connect points of equal depth, resembling shorelines if sea level dropped.
Isobath interval: difference in depth between isobaths.
Index isobaths: darker, thicker isobaths labeled with depth, at intervals 4 or 5 times the regular interval.
Isobaths never divide or split, though they may overlap to represent a vertical cliff.
Isobaths are farther apart on gentle slopes and closer together on steep slopes.

Marine Rocks

Rocks classified into igneous, sedimentary, and metamorphic based on formation.
Sedimentary rocks: form by precipitation of minerals from water or lithification of sediments.
Sedimentary rock characteristics: texture (gravel, sand, mud, crystalline), composition (lithogenous, biogenous, hydrogenous).
Examples: sandstone, breccia, conglomerate, limestone, mudstone, evaporites, chalk, diatomite.
Igneous rocks: form from solidification of magma.
Igneous rock characteristics: texture (phaneritic – large crystals, aphanitic – small crystals), composition (felsic, mafic, ultramafic).
Examples: basalt, granite, peridotite.

Marine Sediments

Classified into 4 categories based on source: lithogenous, biogenous, hydrogenous, and cosmogenous.
Lithogenous (terrigenous): derived from pre-existing rocks.
Biogenous: derived from marine organism shells.
Hydrogenous: precipitated or evaporated from fluids.
Cosmogenous: extraterrestrial material.
Sediments also described by texture (grain size):
- Gravel: pebbles, cobbles, boulders (>2 mm) – associated with high-energy water.
Grain size:
- Sand: (2 - 1/16 mm)
- Silt: (1/16 - 1/256 mm)
- Clay: (<1/256 mm)
This classification focuses on the lithogenous sediment component.
Grain size represents the energy of the environment where the sediment was deposited.

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Description

Test your knowledge on error, precision, and rounding in measurements. This quiz covers unit conversions and how to read a refractometer effectively. Enhance your understanding of scientific instruments and measurement accuracy.