SC.3.P.8.2 Measure and Compare Mass and Volume

SC.3.P.8.2 Measure and compare the mass and volume of solids and liquids.

How Are Mass and Volume Measured?

Matter is anything that takes up space (volume), and has mass, or weight. A basketball for example takes up space. You can feel the weight of a basketball in your hands when you hold it. A basketball is a solid: it doesn’t change its shape when you pick it up and put it down. Water is a liquid. It takes up space. It takes up space inside the cup that is holding it. You can feel the weight of the water in the cup when you hold it. When you dump the water out, the cup will weigh less. Water is a liquid: it will change its shape. When you dumped the water out of the cup, it changed its shape.

We can measure the weight of solids and liquids using a scale. Some scales are digital scales. These are the easiest to use, and are the most accurate. Balance scales, triple beam balance scales, and spring scales are also tools to measure weight. You might be familiar with a spring scale if you have used one to weight a fish.

Measuring cups are used to measure the volume of liquids. Volume is the amount of space an object or material takes up. Graduated cylinders are also used to measure the volume of liquids. Both measuring cups and graduated cylinders can be used to find the volume of a solid. 

The mass of an object is how much the object weighs when resting on the ground. Mass and weight are similar terms: there are important differences that you will learn about in middle school.

A scale is used to find the weight of objects and materials. If you have a bathroom scale at home, you may have used it to find your own weight. When you go to a doctor’s office, the doctor probably uses a balance scale to find your weight.

When cooking in the kitchen, a digital kitchen scale is used to find weight. Simply turn the digital scale on, wait until it reads “0,” and then place the object on it. The digital scale will display the weight of the object on the screen. 

It is easy to find the weight of solids: you just place them on the scale and measure. To find the weight of a liquid is also easy, there are just a couple of extra steps to take.

If you were to place a cup of water on a scale and find the weight, you would find the total weight of the cup and the water. To find the weight of just the water, you simply find the weight of the empty cup, and then subtract that from the total. The difference is the weight of the water alone.

Volume is the amount of space an object or material takes up. It is easy to find the volume of a liquid. Simply pour the liquid (usually water) into a measuring cup or a graduated cylinder and record the volume. Volume is recorded as liters (L) or milliliters (ml). 

Finding the volume of a solid is also easy, there are just a few more steps to finding the volume of solids.

The displacement method is a way to find the volume of a solid. To find the volume of a solid, you begin by choosing a measuring cup or graduated cylinder that the object you are trying to measure will fit into. Next, fill the graduated cylinder about halfway, and round to the next highest ten. For example, if half the cylinder is 25 ml, round up to 30 ml. This is the starting volume of the water.

Next, gently slide the object you are measuring into the graduated cylinder. Let everything come to rest and settle down. You have added a solid to a liquid. Now find the total volume: for example, 45 ml.

45 ml is the total volume of the solid and the liquid. You now subtract the volume of the water: 30 ml. The difference, 15 ml, is the volume of the solid. This method of finding the volume of a solid is called thedisplacement method.

Compare a set of cubes. The cubes are all the same size. They take up the same amount of space. They all have the same volume. We can find the volume of one cube, and since they are all the same size, we can use that volume for each of the others.

To find the volume of one of the cubes, we will use the displacement method. We find a graduated cylinder large enough for the cube to find into. Then, we fill it with water about halfway, and round up to the nearest ten. In this investigation we start with a volume of 20 ml of water.

We then tilt the cylinder to one side, and slowly slide the cube into the water. We stand the cylinder back up, and find the total volume fo the water plus the cube: 30 ml. to find the volume of just the cube, subtract the volume of the water from the total. The difference is the volume of the solid: 10 ml.

Each of the cubes has a different color, texture, and luster. Some of the cubes look like metals, some like wood, and some like plastic. Because they are different materials, we can compare the masses of the cubes.

We place each of the cubes on a digital scale, and record the weight of the cubes in grams (g).

To compare the weights of the cubes, we can create a Venn diagram. Since we already observed that some of the cubes are metal, some are wood, and some are plastic, we’ll use a triple Venn diagram.

We group all of the metals in one section. We’ll record the number of the cube and its weight. Then we will do the same for the wood cubes and for the plastic cubes.

Since the volume of the cubes is all the same, we’ll record that in the center, since that is the one thing that is the same.

Now we can draw some conclusions based on our data. The set of metal cubes was the heaviest. The set of plastic cubes was the lightest. The wood cubes were in the middle.

Based on our data, we can conclude that wood is lighter than metal, and heavier than plastic. All of the cubes have the same volume. We have successfully measured and compared the volume and mass of solids and liquids.