How to Find the Mass of an Object: Study Guide

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The Matter At Hand

Matter is the stuff that makes up physical objects. You, your pet, your desk, a pen, the lamp and your computer are all made up of matter. (You may already know about one type of matter–the atom.) Aside from naming the things that are made of matter, we also have different ways of measuring matter. These measurements are systems of communication in science and mathematics. They make it so that we can compare and talk about different objects.

Measuring Matter

• Can you think of some standard scientific measurements?
• What tools do we use to measure matter?
• What is the unit of that measurement?

Here are some ideas to get you brainstorming:

• Temperature is a measurement of the warmth or coolness of an object. We can measure temperature with a thermometer. We can also approximate temperature with our bodies through touch. In the US we use two different labels for temperature because we use both the imperial and metric measurement systems: Fahrenheit and Celsius.
• Circumference is the distance around an object. We usually measure circumference with a flexible ruler called a tape measure. Circumference may be labeled with any unit of length. Imperial measurements include inches, feet, yards and miles. Metric measurements include millimeters, centimeters, meters and kilometers.

Wondering how to find the mass of an object? Mass is just another physical property of matter that we can measure. It tells us how much matter is packed into an object.

I Have All The Other Measurements. Why Do I Need Mass?

We use length, width, height and depth to talk about the size of an object. With these measurements we can easily compare different things.

1. Would you rather live in a 100-foot tall building or a 10-foot tall building?
2. Would you rather buy a 2-inch long candy cane or a 12-inch long candy cane?

But how do you compare a 1-inch magnet with a 1-inch feather? You might describe the color and shape. But how to you describe the way the object feels in your hand?

When you use words like “heavy” and “light” you are talking about the mass of the object. The magnet is heavier than the feather because it has more stuff–more matter–packed into the same amount of space. The heaviness or lightness you feel is the effect of Earth’s gravitational pull.

The more matter, the more mass, the greater the gravitational pull, the heavier something feels.

Whice Object Has Greater Mass?

o A cannonball or a basketball?
o A lightbulb or a baseball?
o A book or box of chocolate?
o An egg or 3 bees?
o A pencil or a pen?
o A dry towel or a wet towel?

The Tricky Part

Many people confuse mass with another measurement called weight. But mass and weight are not the same thing.

Since mass is the amount of matter in an object, it does not change when the object is moved to another location. Your mass will be the same on Earth, the Moon, Pluto and Mars.

But your weight will change.

Weight is a measurement that describes the amount of force gravity exerts on an object. This measurement will change depending on the gravitational pull at the location of measurement. If you measure your weight on Earth it will be different on the Moon–you will weigh less because the Moon has a smaller gravitational pull.

Did you know astronauts have been known to get sick from the sensation of being weightless? This condition is called SAS (Space Adaption Syndrome). Although they train to avoid it, astronauts can suffer from nausea, dizziness, disorientation and vomiting! Gross!

Having Trouble Remembering The Difference?

Just look at the first letters of Mass and Weight.

“M” is a sturdy letter that stands on its own. It won’t be pushed around so we know it will stay the same no matter what.

“W” is a wobbly worm. It sits on its bottom and wiggles around. “W” can’t stand on its own–so its sure to change. Just like your weight!

Measuring Mass

Can you guess what tool we use to measure mass? It’s a scale! The triple-balance beam scale is the standard tool used for measuring the mass of small objects. It will give you a precise measurement in kilograms.

Things You’ll Need:

o Triple-balance beam scale
o Object
o Pen
o Paper

What To Do:

1. Empty the plate. Turn the calibration screw until the balance beam zeroes out. The arrow on the beam will point to a “0.”
2. Place an object on the scale pan.
3. Move the slider on the beam to the estimated weight of the object.
4. Look at the left side of scale where the “0” indicator is located. Move the slider to a higher number if the indicator points above the “0.” Move the slider to a lower number if the indicator points below “0.”
5. When the arrow points to “0”, look at the three beams. Each beam will have a slider on it that points to a specific number. Add up these three numbers for the total mass. For example, if the beams read 1kg, 5kg and 200kg, the mass is 206kg.
6. Take the object off the pan and measure it again.