mass and weight experiment

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Mass & Weight Science Projects

Make a balance.

Learn how you can use a plastic hanger and some paper cups to make a balance and compare the mass of different objects!

What You Need:

• Plastic coat hanger
• String or yarn
• Two paper cups
• Wooden skewer

What You Do:

1. Ask an adult to carefully poke two holes in each cup using the wooden skewer. The holes should be a little below the cup’s rim and directly across from each other.

2. Cut two pieces of string about two feet long. They need to be the same length.

3. Make a cup handle: Use the skewer to push an end of one piece of string through one of the holes in one cup. Tie the end in a knot so it is securely attached to the rim of the cup. Push the other end through the hole on the opposite side of the cup and tie it.

4. Do the same thing with the other cup and piece of string. The loops of string on each cup need to be exactly the same length so that the cups will hang evenly on your scale. Before you tie the second side, check to make sure they are the same.

5. Find a place to hang your scale. You need a place where it can hang freely without bumping into anything. A shower curtain rod works well. Have an adult tie a piece of string to the hanger’s hook and tie the other end around the curtain rod so that the hanger is easy for you to reach.

6. Now hang the loop of each cup on one of the small clothing hooks on each side of the hanger. The hanger should be balanced and the cups should hang down at equal levels on each side.

7. Now you can experiment with your balance! What happens if you add an object to the cup on one side but not the other? Can you find an object to put in the other cup that will make the cups balance again?

What Happened:

You just made a balance. You can use it to compare the the mass of different objects. All things are made up of matter .

Mass is a measure of the amount of matter that an object has, or how much “stuff” it is made up of.

How does the balance work? Since the paper cups are the same size and made from the same material and the strings you used were the same length, the hanger balanced evenly because each side had the same mass.

Notice that if you take one cup off, the balance tips so that the side without the cup goes up in the air!

That’s because the mass from the other cup is pulling down on the hanger. When you put the cup back on, the hanger is balanced again and the cups are level.

If you place a quarter in the cup on the left, the balance tips. The coin adds more mass to the left side, so it tips down and the right side with the empty cup goes up.

If you put a dime in the cup on the right, its mass will push the cup down. It has less mass than the quarter, though, so the right side will still be higher.

If you add a penny to the cup on the right, the mass will change even more and the balance will move again. This time the cups should balance.

Now the mass in each cup is the same (or almost the same) and the cups balance each other again. A quarter has the same mass as one dime plus one penny! You can compare the mass of lots of different objects with this balance.

Do you know the difference between mass and weight?

Mass is a measure of how much matter is in an object, but weight is a measure of how much gravity is pulling on the object.

Gravity is a force that affects us all the time.

(You’ll learn more about it later. For now, you just need to know that there is less gravity on the moon than there is on Earth.)

When you stand on a bathroom scale, it tells you how much you weigh. It doesn’t tell you how much mass you have.

A scale measures how much force is pushing down on it. When you stand on it, it measures how much gravity is pulling down on you while you are pushing down (in other words, standing) on it.

If you could go to the moon and stand on your bathroom scale, you would find that you weigh much less than you do on Earth, because there would be less gravity pulling down on your body as you stand on the scale.

So, what do you think would happen if you could use your hanger balance in space, where there is less gravity pulling on objects?

Since your balance only compares the mass of objects, not their weight, you would get the same results on the moon as you do on earth!

Even on the moon, a quarter on one side of your balance would still have the same mass as a dime and penny on the other side of the balance.

The coins would weigh less on the moon, but their mass would not change! Objects still have the same mass—amount of “stuff” in them—no matter how much or how little gravity pulls on them.

Ball vs. Feather

Which object do you think will fall to the ground faster, a ball or a feather? Test it out and learn why with this experiment.

• a small ball
• a feather or a tissue
• two sheets of paper

1. Hold the ball in one hand and the feather or tissue in the other.

2. While standing up, hold your arms out in front of you with the backs of your hands facing up.

3. Open both of your hands at the same time and watch the objects fall. Which one reaches the floor first?

4. Now try dropping the ball and a sheet of paper (hold your hand flat under the paper and then pull your hand out to let it drop). Which one makes it to the floor first?

5. Crumple one sheet of paper into a ball. Drop the paper ball and the full sheet of paper at the same time. What happens?

6. Now drop the ball and the paper ball at the same time and notice what happens.

Even though you dropped both objects from the exact same height, the ball hit the ground much sooner than the feather (or tissue).

You probably found that the ball also reached the floor before the sheet of paper. Can you explain why?

In step 5, you probably found that the paper ball hit the floor several seconds before the sheet of paper did. Both pieces of paper had the same mass, so why did one get to the floor before the other?

You can try it again if you like, to see if you can get the sheet of paper to reach the ground at the same time as the ball of paper, but you will find that the ball always gets there first! The results of step 6 might have surprised you even more. The paper ball reached the floor at the same time as the regular ball! How is that possible?

Mass and weight do not determine how quickly an object will fall to the ground. It’s easy to think that the ball will fall first because it has more mass.

To understand this, you need to know what makes objects fall. The force of gravity is what causes objects to fall. If you throw or kick a ball into the air, it will eventually come back down, because gravity is pulling down on it. All objects actually fall at the same speed, because gravity pulls on them equally, no matter how heavy they are!

That explains why the paper ball and the regular ball landed on the floor at the same time, but why didn’t the sheet of paper, tissue, or feather fall as quickly?

Well, it turns out that objects will only fall at the same speed if no other force is acting on them.

So they started out falling at the same speed, but after falling a few centimeters, the air started pushing up against the objects just as gravity was pulling down on them.

Since a ball is round and smooth, the air couldn’t resist it very much and the force from gravity that was pulling down on it was still stronger than the force of the air pushing up against it.

However, the feather, tissue, and paper were affected by air resistance. Air that was caught underneath the objects pushed up against them and their fall was slowed down.

The shape of an object has a lot to do with how much air resistance will affect it. Think about a parachute falling to the ground.

Why do you think it falls to the ground slowly enough to keep a person from getting hurt when he or she lands on the ground? It’s because of the air that gets caught under the parachute and pushes back up against the force of gravity that is pulling it down.

The air actually slows the parachute down as it is falling!

To learn more about mass, weight, and gravity, visit this Teaching Tip.

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Mass Vs. Weight Lab Activities

People often use the words "mass" and "weight" interchangeably, but these words have different meanings. Mass refers to the amount of matter in an object, and it is not dependent on gravity; your mass on Earth would be the same on the moon. Weight, on the other hand, measures heaviness of an object, or the strength of gravitational pull on that object. Your weight would change between the Earth and moon because the gravity is different in both places.

Weight on Different Planets

After introducing the idea that weight depends on gravity, teach students how to calculate their weight on different planets. The basic formula is: weight = mass X surface gravity. Provide students with a list of surface gravities of different planets, such as 0.38 for Mercury and 1.06 for Saturn, according to Live Science. Prompt each student to multiply his weight with the surface gravity to find his weight on each celestial body. Students might be surprised to find that a person who weighs 140 pounds on Earth would weigh a laughable 8.4 pounds on Pluto.

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More For You

Would your weight change if you were standing on the moon, fifth grade science experiments on h2o evaporation, jupiter's length of rotation & revolution, does a balloon with helium rise higher than one with oxygen, activities on climate and weather for fifth grade, measuring mass.

One way people measure mass is with a balance. While you might think the balance measures weight, the mass measured with a balance would be the same on Earth and other planets because the balance weights also change to the same degree as what you're measuring. Ask students how much mass they think various objects have, and measure them on a balance scale to see who had the closest answer.

The Pull of Gravity

Students can observe gravity and weight by measuring the pull of objects on a rubber band. Cut two rubber bands to create long strings. Tape one end of a rubber band to the top of a full juice pouch, and tape the other rubber band to an empty juice pouch. Fill the empty juice pouch with air by blowing into the hole and seal it with tape. Hold the other ends of each rubber band at chest level and observe how far the juice pouches stretch the rubber band; the full pouch will sink lower because it has more weight.

Falling Objects

According to PBS Learning Media, objects fall at the same speed regardless of their mass. Measure a whole apple and half of an apple on a balance with your students and note the difference in mass. Ask students if they believe the apples would hit the ground at the same or different times. Drop the whole and half apples from the same height and watch them hit the ground simultaneously.

• National Park Service: Mass and Weight
• Live Science: How Much Would You Weigh on Other Planets?
• Jefferson Lab: What Do We Use to Measure Mass?
• PBS Learning Media: Gravity and Falling Objects
• University of California Los Angeles: Mass, Weight and Density

Cara Batema is a musician, teacher and writer who specializes in early childhood, special needs and psychology. Since 2010, Batema has been an active writer in the fields of education, parenting, science and health. She holds a bachelor's degree in music therapy and creative writing.

Wait, Weight, Don't Tell Me!

A simple chemistry experiment—adding baking soda to vinegar—seems to challenge the law of conservation of mass.

Video Demonstration

• Safety goggles
• Baking soda (sodium bicarbonate)
• Vinegar (standard 5% acetic acid)
• Flask or bottle
• Measuring cup
• Balance scale that reads to at least 0.1 gram
• Optional: extra materials to experiment with, such as more balloons, zip-seal sandwich bags, 2-liter plastic bottles, etc.

• Put on your safety goggles.
• Attach a balloon to the end of the funnel.

• Pour about 1/2 cup (120 mL) of vinegar into the bottle or flask.

To begin, carefully put the sealed flask onto the scale and write down its starting weight.

You’re about to tip the balloon’s contents into the flask. What do you think will happen? Will the weight go up, down, or stay the same? Why?

Write down the final weight when the reaction is over.

Surprise—your balloon swelled enormously, but the weight actually dropped.

This result is especially confounding if you happen to be familiar with the law of conservation of mass : In any closed system, mass is neither created nor destroyed by chemical reactions or physical transformations. In short, the mass of the products of a chemical reaction must equal the mass of the reactants.

Did you really just violate the law of conservation of mass? You might be dying to know what’s going on, but wait, weight—why not figure it out for yourself?

The answer is below…but to avoid a spoiler, skip down to the Going Further section before reading on.

Alright, here’s the answer: Besides the chemical reaction, the only thing that changed in your sealed system was the volume . When you added the baking soda to the vinegar, the two combined to make carbon-dioxide gas, which inflated the balloon.

The expansion of the balloon changed the weight of your sealed flask because you and your entire experiment are submerged in a fluid: air.

Just like water, air is a fluid, and fluids buoy up objects. The upward buoyant force on any submerged object is equal to the weight of the fluid displaced by that object—this is known as Archimedes’ principle . By increasing the volume of your sealed flask, you cause it to displace more air, increasing the buoyant force on it and reducing its weight. Here's the thing to remember: Scales measure weight, not mass. The mass stayed the same due to the law of conservation of mass, but because of buoyancy, the weight went down!

Consider possible explanations for the weight change: Did the balloon leak? Did something funny happen to the scale? What else might be going on? Plan an experiment to test your theory, gather equipment, and carry it out.

For an illuminating variation on the original experiment, try combining your chemicals while they’re sealed inside a 2-liter bottle. Getting things to mix only after you’ve sealed the bottle is an engineering design challenge unto itself. Caution: Do not exceed the recommended amounts of 1/2 cup (120 mL) vinegar and 2 teaspoons (10 mL) baking soda.

To confirm Archimedes’ principle, measure the volume of the balloon and use the known density of air (0.001225 g/cm 3 at 15° C at sea level) to calculate exactly the weight of air displaced by your expanding balloon. Does the weight loss of your flask match the theoretical prediction?

This activity is meant to spark more experimentation. Having a variety of supplies on hand will allow for creative investigation into this phenomenon.

This idea was first introduced to us by visiting fellow Eleanor Duckworth of Harvard University.

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Mass vs Weight – The Difference Between Mass and Weight

The difference between mass and weight is the mass is a measure of the amount of matter in an object, while weight is a measure of the effect of gravity on that mass. In other words, gravity causes a mass to have weight. The relationship between mass and weight is a simple equation: W = m * g Here, W is weight, mass is mass, and g is gravity People often use the words “mass” and “weight” interchangeably because gravity is pretty much constant on Earth, so there isn’t a difference between their values. But, if you compare weight on Earth to a different place, like the Moon, you get different values. Your mass on the Moon remains the same, but your weight is different because the acceleration due to gravity is different there.

The Difference Between Mass and Weight

There are several differences between mass and weight.

Mass is an intrinsic property of matter . It doesn’t change depending on where you measure it. It is a scalar value , which means it has magnitude, but no direction associated with it. The mass of an object is never zero . You measure mass with an ordinary balance on Earth or an inertial balance in space.

Weight depends on the effect of gravity, so it can change depending on where it’s measured. In the absence of gravity, weight can be zero. Because weight is a force , it is a vector quantity. It has both magnitude and direction. You measure weight using a spring balance.

Units of Mass and Weight

We measure weight in grams, kilograms, ounces, and pounds. Technically, grams (g) and kilograms (kg) are units of mass. The SI unit of force is the Newton (N), with a 1 kg mass having a force of 9.8 N on Earth. The US unit of force is the pound (lb), while the unit of mass is something called a slug. A pound is the force required to move a 1 slug mass at 1 ft/s 2 . One slug has a weight of 32.2 pounds.

While it’s fine to use pounds and kilograms interchangeably for most practical purposes, in science it’s best to use kilograms for mass and Newtons for force.

Mass vs Weight Activities

Weight in an elevator.

One simple activity to see the difference between mass and weight is weighing yourself in an elevator. A digital scale works best because it’s easier to see the change in weight as the elevator ascends (increasing acceleration, which adds to gravity) and descends (negative acceleration, which decreases the effect of gravity). For a classroom activity, first have students weigh themselves (or an object) on a scale and discuss whether the value they obtain is mass, weight, or whether it matters. Next, have them make predictions about what will happen in an elevator and conduct the experiment to test their hypothesis .

It can be a challenge to explore the difference between mass and weight on Earth because gravity is all around us. Fortunately, the astronauts on the International Space Station (ISS) conducted experiments that complement activities on Earth. Follow along with the video and compare what happens in microgravity compared to Earth.

Measuring Weight With Rubber Bands

You can compare the weights of objects by hanging them from rubber bands. On Earth, gravity affects a heavier object more than a lighter one and stretches the rubber band further. Predict what will happen when heavy and light objects are suspended from rubber bands on the ISS. What shape will the rubber band take? Do you expect there to be a difference between the way the rubber band responds to a heavy object compared to a light object?

The easiest way to explore mass on Earth is to conduct experiments that move horizontally rather than vertically. This is because objects can’t change their position from the effect of gravity. Build a “mass car” and use an air pump to accelerate the mass across rollers or a low-friction track. Change the mass of the car, make a prediction about how this will change how far the car rolls, and perform an experiment to test the hypothesis. You can graph the distance the car moves compared to its mass. Predict whether the results will be different in space and use the ISS experiment to reach a conclusion.

Accelerating Mass With a Tape Measure

If you can’t build a mass car or get an air pump, you can use a retractable tape measure to apply acceleration to an object. Do this by pulling out the measuring tape one meter or three feet and attaching the end to an object. Secure or hold the tape measure and click the button to retract the tape. Does it take the same amount of time to retract the tape with a heavier object compared to a lighter one? What does this say about the acceleration produced by the tape measure? Ask students to make predictions and explain results. Make a prediction about what will happen on the ISS and see if you’re correct.

• Galili, Igal (2001). “ Weight versus Gravitational Force: Historical and Educational Perspectives .”  International Journal of Science Education . 23(1): 1073-1093.
• Gat, Uri. (1988). “The Weight of Mass and the Mess of Weight.”  Standardization of Technical Terminology: Principles and Practice . ASTM. 2: 45-48.
• Hodgman, Charles D., editor. (1961). Handbook of Chemistry and Physics (44th ed.). Chemical Rubber Co. 3480-3485.​
• Knight, Randall Dewey (2004).  Physics for Scientists and Engineers: a Strategic Approach . Pearson.
• Morrison, Richard C. (1999). “ Weight and Gravity—The Need for Consistent Definitions .”  The Physics Teacher . 37(1).

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Weight and Mass

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Use a balance to measure mass and a spring scale to measure the weight of objects. Compare the masses and weights of objects on Earth, Mars, Jupiter, and the Moon.

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