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# Scientific Measuring Devices

## Discusses how to correctly use instruments for measuring volume and mass.

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Scientific Measuring Devices
• I can use a ruler to measure length.
• I can use a balance to measure mass.
• I can use a spring scale to measure weight.
• I can use a graduated cylinder to measure volume.
• I can use a microscope to view objects that are too small to be seen with the naked eye.

The device pictured above is called a pH meter. It is a scientific measuring device that measures the acidity of a liquid. Being able to use scientific measuring devices such as this is an important science skill. That’s because doing science typically involves making many measurements. For example, if you do lab exercises in science, you might measure an object’s length or mass, or you might find the volume of a liquid. Scientists use sensitive and specific measuring devices to make measurements such as these. The measurements are usually made using SI units of measurement that you learned about in the previous section.  This section will address a wide variety of tools used by scientists.  You will also look more deeply a measurement techniques later this year in Unit 4 when you learn about matter.

### Measuring Length with a Metric Ruler

You’ve probably been using a ruler to measure length since you were in elementary school. But you may have made most of the measurements in English units of length, such as inches and feet. In science, length is most often measured in SI units, such as millimeters and centimeters. Many rulers have both types of units, one on each edge. The ruler pictured below has only SI units. It is shown here bigger than it really is so it’s easier to see the small lines, which measure millimeters. The large lines and numbers stand for centimeters. Count the number of small lines from the left end of the ruler (0.0). You should count 10 lines because there are 10 millimeters in a centimeter.

Q: What is the length in millimeters of the red line above the metric ruler?

A: The length of the red line is 32 mm.

Q: What is the length of the red line in centimeters?

A: The length of the red line is 3.2 cm.

### Measuring Mass with a Balance

Mass is the amount of matter in an object. Scientists often measure mass with a balance. A type of balance called a triple beam balance is pictured in Figure below. To use this type of balance, follow these steps:

1. Place the object to be measured on the pan at the left side of the balance.
2. Slide the movable masses to the right until the right end of the arm is level with the balance mark. Start by moving the larger masses and then fine tune the measurement by moving the smaller masses as needed.
3. Read the three scales to determine the values of the masses that were moved to the right. Their combined mass is equal to the mass of the object.

A triple beam balance

The Figure below is an enlarged version of the scales of the triple beam balance in Figure above. It allows you to read the scales. The middle scale, which measures the largest movable mass, reads 300 grams. This is followed by the top scale, which reads 30 grams. The bottom scale reads 5 grams. Therefore, the mass of the object in the pan is 335 grams (300 grams + 30 grams + 5 grams).

Notice the middle beam reads 300 grams, the top beam reads 30 grams, and the bottom beam reads 5 grams. The total mass of the pan is 335 grams.

Q: What is the maximum mass this triple beam balance can measure?

A: The maximum mass it can measure is 610 grams (500 grams + 100 grams + 10 grams).

Q: What is the smallest mass this triple beam balance can measure?

A: The smallest mass it can measure is one-tenth (0.1) of a gram.

To measure very small masses, scientists use electronic balances, like the one in the Figure below. This type of balance also makes it easier to make accurate measurements because mass is shown as a digital readout.

An electronic balance[Figure1]

In the picture, the balance is being used to measure the mass of a white powder on a plastic weighing tray. The mass of the tray alone would have to be measured first, then subtracted from the mass of the tray and powder together. The difference between the two masses is the mass of the powder alone. Another way to measure the mass of the powder alone is to first place the plastic weighing tray on the scale, then press the "Zero" button.  This will remove the mass of the tray and set the scale to zero. After the scale has been zeroed, it will just display the mass of any powder that is added.  Scientists call this process of zeroing the mass of the weighing tray "taring the scale."

### Measuring Weight with a Spring Scale

Have you ever been fishing and weighed your catch before keeping it or releasing it?  Or, have you ever used a hanging basket at the grocery store to weigh the produce you are planning to buy?  If so, you have probably used a spring scale.  Scientists also use spring scales to measure the weight, or the force of gravity, of an object..  Although, you probably measured the weight of the fish you caught or the grapes you planned to buy in ounces or pounds, when using a spring scale in science class, you will notice it measures weight in Newtons.  Newtons are a force unit used in the SI system.  You can learn more about how a spring scale works in the video at this URL: https://www.youtube.com/watch?v=FbVP9_ZCi_A

This figure shows an example of a spring scale. Although they may take different forms, they usually have a hook to hang the object whose weight is to be measured and a spring that stretches based on the weight of the object. Notice this spring scale measures up to 10N.[Figure2]

### Measuring Volume with a Graduated Cylinder

Volume is the amount of space that matter occupies.  At home, you might measure the volume of a liquid with a measuring cup. In science, the volume of a liquid might be measured with a graduated cylinder, like the one sketched below. The cylinder in the picture has a scale in milliliters (mL), with a maximum volume of 100 mL. Follow these steps when using a graduated cylinder to measure the volume of a liquid:

1. Place the cylinder on a level surface before adding the liquid.
2. After adding the liquid, move so your eyes are at the same level as the top of the liquid in the cylinder.
3. Read the mark on the glass that is at the lowest point of the curved surface of the liquid. This is called the meniscus.

Q: What is the volume of the liquid in the graduated cylinder pictured above?

A: The volume of the liquid is 67 mL.

Q: What would the measurement be if you read the highest point of the curved surface of the liquid by mistake?

A: The measurement would be 68 mL.

While measuring the volume of a liquid is pretty straightforward, measuring the volume of an irregularly shaped solid, such as a rock, is a little more complicated.  Scientists use a process known as the displacement method to measure the volume of irregularly shape solids. Here are the steps they follow:

1. Fill a graduated cylinder to a given volume (be sure to leave room at the top of the cylinder).
2. Record the starting volume.
3. Place the solid in the cylinder.  It will displace (push away) the water in its place and cause the water to rise in the cylinder.
4. Record the final volume.
5. Subtract the initial volume from the final volume.  That volume is equivalent to the volume of the irregularly shaped solid.

Credit: Michael Malak

Q: What is the volume of the rock in the picture above?

A: The volume is approximately 3ml (final volume 23 ml - initial volume 20ml)

While graduated cylinders are the most appropriate instrument to measure the volume of liquids and irregularly shaped substances, the volume of regularly shaped solids, such as cubes and right rectangular prisms (boxes), can be calculated pretty simply using mathematics.  You may have learned in math class that their volumes can be calculated by using the following equation:  V = l x w x h (where V=volume, l=side length, w=side width, and h=side height).

Can you calculate the volume of the box in the figure? If you found it to be 54 cubic meters, you are correct! Explain how you calculated the volume.[Figure4]

### Measuring Temperature with a Thermometer[Figure5] License: CC BY-NC 3.0

This boy has a fever, and it makes him feel miserable. He feels achy and really tired. He also feels hot because his temperature is higher than normal. He has a thermometer under his armpit to measure his temperature. No doubt you already have a good idea of what temperature is. You might say that it’s how warm or cool something feels. In science, temperature is defined as the average kinetic energy of the particles of matter. When particles of matter move more quickly, they have more kinetic energy, so their temperature is higher. With a higher temperature, matter feels warmer. When particles move more slowly, they have less kinetic energy on average, so their temperature is lower. With a lower temperature, matter feels cooler.

#### How a Thermometer Measures Temperature

Many thermometers measure temperature with a liquid that expands when it gets warmer and contracts when it gets cooler. Look at the common household thermometer pictured in the Figure below. The red liquid rises or falls in the glass tube as the temperature changes. Temperature is read off the scale at the height of the liquid in the tube similar to how a graduated cylinder is used to measure volume. To learn more about measuring temperature, watch the animation “Measuring Temperature” at this URL: http://www.sciencehelpdesk.com/unit/science2/3

Can you read the Celsius and Fahrenheit temperatures on the thermometers in the figure?

Q: Why does the liquid in the thermometer expand and contract when temperature changes?

A: When the temperature is higher, particles of the liquid have greater kinetic energy, so they move about more and spread apart. This causes the liquid to expand. The opposite happens when the temperature is lower and particles of liquid have less kinetic energy. The particles move less and crowd closer together, causing the liquid to contract.

#### Temperature Scales

The thermometer pictured in the Figure above measures temperature on two different scales: Celsius (C) and Fahrenheit (F). If you live in the U.S., you are probably most familiar with the Fahrenheit scale; however, scientists are more likely to use the Celsius scale The Table below compares the two temperature scales. Each scale uses as reference points the freezing and boiling points of water

Scale Freezing Point of Water Boiling Point of Water
Celsius 0 °C 100 °C
Fahrenheit 32 °F 212 °F

Because both temperature scales are frequently used, it’s useful to know how to convert temperatures from one scale to another. Converting between Celsius and Fahrenheit is a bit complicated. The following conversion factors can be used:

Celsius → Fahrenheit: (°C × 1.8) + 32 = °F

Fahrenheit → Celsius: (°F - 32) ÷ 1.8 = °C

For example, to convert 10 °C to Fahrenheit, use the first conversion factor:

(10 °C × 1.8) + 32 = 50 °F

Q: The weather forecaster predicts a high temperature today of 86 °F. What will the temperature be in Celsius?

A: To convert 86 °F to Celsius, use the second conversion factor:

(86 °F – 32) ÷ 1.8 = 30 °C

### Using a Microscope to Observe Small Objects

Microscopes, tools that you may get to use in your class, are some of the most important tools in biology (Figure below). A microscope is a tool used to make things that are too small to be seen by the human eye look bigger. Microscopy is the study of small objects using microscopes. Look at your fingertips. Before microscopes were invented over 400 years ago in 1595, the smallest things you could see on yourself were the tiny lines in your skin. But what else is hidden in your skin?

Notice the microscope in the figure has multiple lenses extending from it. These magnify slides to varying degrees, depending on how much detail the scientist is wanting to see.

Basic light microscopes opened up a new world to curious people.

Watch the video at the following URL to understand better how to use a microscope: https://www.youtube.com/watch?v=bGBgABLEV4g

### Vocabulary

• mass:  the amount of matter in an object
• triple beam balance: a type of mechanical balance used to measure mass
• electronic balance: a type of balance often used to measure very small masses or make very accurate measurements
• volume:  the amount of space that matter occupies
• graduated cylinder: a tool used to measure volume of a liquid
• meniscus: the lowest point of the curved surface of a liquid
• displacement method: method for measuring the volume of an irregularly shaped solid that involves placing the solid in a given volume of liquid and measuring how much the water level rises
• temperature:  the average kinetic energy of the particles of matter
• microscope: a tool used to make things (usually on slides) that are too small to be seen by the human eye look bigger

### Opportunity for Extension

A micrometer is a measuring device that is used to make precise measurements of very small distances. At the URL below, read about the parts of a micrometer and how to use it. Then test your skills by reading a virtual micrometer. Be sure to check your answers at the bottom of the test page. If you need more practice, click on the “Try more” link below the answers.

http://feh.eng.ohio-state.edu/tutorials/micrometer/micindex.html

### Review

1. Using the enlarged metric ruler segment shown below, what is the length of the blue line in centimeters?

1. Assume that an object has been placed in the pan of a triple beam balance. The scales of the balance are shown below. What is the mass of the object?

1. How much liquid does this graduated cylinder contain?

4.  What is temperature?

6.  Assume that the temperature outside is 293 Kelvin but you’re familiar only with the Fahrenheit scale. Do you need to wear a hat and gloves when you go outside? To find out, convert the Kelvin temperature to Fahrenheit. (Hint: Convert the Kelvin temperature to Celsius first.)

### Missouri Standards

• 1.1.A.b:  Describe and compare the volumes (the amount of space an object occupies) of objects or substances directly, using a graduated cylinder, and/or indirectly, using displacement methods
• 1.1.A.c: Describe and compare the masses (amounts of matter) of objects to the nearest gram using a balance
• 7.1.B.b:  Determine the appropriate tools and techniques to collect data
• 7.1.B.c: Use a variety of tools and equipment to gather data (e.g., microscopes, thermometers, computers, spring scales, balances, magnets, metric rulers, graduated cylinders, stopwatches)
• 7.1.B.d: Measure length to the nearest millimeter, mass to the nearest gram, volume to the nearest milliliter, temperature to the nearest degree Celsius, force (weight) to the nearest Newton, time to the nearest second
• 7.1.B.e: Compare amounts/measurements
• 7.1.B.f:  Judge whether measurements and computation of quantities are reasonable
• 7.1.C.a: Use quantitative and qualitative data as support for reasonable explanations (conclusions)

### Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes

1. [1]^ License: CC BY-NC 3.0
2. [2]^ License: CC BY-NC 3.0
3. [3]^ Credit: Michael Malak; License: CC BY-NC 3.0
4. [4]^ License: CC BY-NC 3.0
5. [5]^ License: CC BY-NC 3.0
6. [6]^ License: CC BY-NC 3.0

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