Return to Lab Menu. Mass, Volume and Density

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1 Return to Lab Menu Mass, Volume and Density Objectives: -to measure different volumes of liquid -to understand that masses are additive but volumes are not necessarily additive -to understand the concept of density and how it is determined Equipment/Materials: sugar water large grained solid (e.g. dried beans, M & M or Tic-Tac candies, choose something that has a reliably regular size and shape and that is fairly sturdy i.e. not apt to flake away when shaken or stirred like Cheerios would) small grained solid (e.g. sugar, salt, fine grained sand) volume measuring devices (measuring cup or graduated cylinder, medicine dropper, measuring spoons) balance set up from previous experiment (balance, standard weights, etc.) Introduction Let s start with some definitions: mass is defined as a measure of the quantity of matter in a body volume is defined as the amount of space a body occupies in three dimensions, and density is the ratio of the mass of an object to its volume. You are probably more familiar with units of volume than units of mass or density. In cooking, you typically make volumetric measurements in cups, teaspoons, and quarts. In the U.S., we buy our gasoline in gallons. Storage space is described in cubic feet. You are also familiar with metric volumetric measurements: you buy soda pop in 2 liter bottles, and automobile engines are described in liters as well. Mass is actually not the same thing as weight, but we will not distinguish between the two at this level, except to say that mass is independent of gravity whereas weight is not. Thus you would have the same mass on Jupiter as on the moon but your weight would be considerably different. AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 1 of 7

2 The measurements most commonly made in a chemistry laboratory are those of mass (milligrams, grams, and kilograms) and volume (milliliters and liters), and your kitchen "laboratory" will be no exception. Volume measurements are straightforward, especially in a kitchen. When you add two separate masses together, the total mass is the sum of the two individual masses. This is because the mass of a substance is independent of where that substance is. For example if you place 10.0 grams of water into a glass that weighs 25.0 grams the mass of the water plus the glass will be 35.0 grams: 10.0 g water g glass = 35.0 g glass of water Thus masses are additive. Volumes on the other hand are not necessarily additive, although they can be. If you have ever packed a suitcase, you know this to be true. The clothes that occupy several cubic feet in your closet can be packed into the much smaller space that is your suitcase. On the other hand if you add 20 ml of pure water to 30 ml of pure water, you will wind up with a total volume of 50 ml. Now let s explore density, which connects mass and volume. Remember the old joke, Which is heavier a pound of lead or a pound of feathers? Even though a pound is always a pound, we think of lead as being heavier than feathers because it has such a large density. Remember that density is defined as mass per unit volume and can be expressed by the equation: m d = V where d = density m = mass V = volume If there is a large mass in a small volume, the value of the density is large. From a scientific standpoint, this means that the atoms or molecules have a large mass and are packed in closely together with not much space between them. Metals fall into this category. The atoms of metals have lots of protons and neutrons and thus have a large mass (e.g. lead atoms have around 207 neutrons and protons!). They are also strongly attracted to each other so that they are nestled in close together. Thus there is a large amount of matter (mass) in a small volume: high density. Conversely, if there is a small mass in a large volume, the density is low. This means that the molecules are relatively light or not packed very tightly together. Helium is an atom of very low mass (only two protons and two neutrons) and because it is a gas, there is a lot of space between the atoms. Thus helium has a very low density and can float above air. Whether an object floats or sinks relative to another is directly related to its density not its mass. A 4.0 g cork will float on water because it is less dense than water. Suppose the cork had a mass of 1000 kg. This very large cork would still float because its density is still less than that of water. Conversely, even a tiny g piece of iron AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 2 of 7

3 will sink because its density is far greater than that of water. Some liquids have a greater density than others. Can you think of a liquid that is less dense than water? More dense than water? There is a photograph of a density column (liquids of different density) that you can view at We describe density as an intrinsic property because its value doesn t depend on the quantity of the substance. A piece of iron with a mass of g has the same density as a piece that has a mass of 200 g. Similarly if you measure the density of a small volume of a sugar (as you will in this experiment), you will find it to have the same density as a larger volume. In this experiment you will use your newly constructed balance to make mass measurements as well as a variety of tools to make volume measurements. You will explore the density of a mixture of solids and of a of sugar in water. Procedure 1. Determining the Volume of a Substance In a kitchen, there are numerous ways to accomplish this. The simplest is to simply pour the substance into a measuring cup and read the level of the substance off the side of the cup. Alternatively, if you are responsible for determining both the volume and the mass, you can add the substance to the balance from the measuring cup. You measure out a specific amount, say 150 ml, and then start transferring the desired amount to the balance. After you have weighed out the amount you want, suppose you have 115 ml left in the measuring cup. Thus the volume of substance on the balance has a volume of 35 ml. You accomplish a similar procedure using a graduated medicine dropper. Below is a table of approximate English metric volumetric conversion factors: English Metric 1 teaspoon 0.5 ml 8 1 teaspoon 1.0 ml teaspoon 2.0 ml 1 teaspoon 5.0 ml 1 tablespoon 15.0 ml Practice measuring the volume of different amounts of a liquid (e.g. water) and determining the metric volumes. AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 3 of 7

4 2. Mixture of Two Solids Weigh out 20 g of your large grained solid (beans, candies, etc.) Transfer it to a device that measures volume and determine its volume in ml. Calculate its density. Weigh out 20 g of your small grained solid (salt, sugar, or fine sand). Measure its volume in ml. Calculate its density. Mix the two solids together. Gently stir or shake the mixture such that the small grained solid can intersperse completely with the larger grained solid. Measure the mass. Measure the volume. Determine the density. 3. Solution of sugar and water Weigh out 20.0 g of sugar. Determine its volume in ml. Weigh out 20.0 g of water. Determine its volume in ml. Add the sugar to the water and stir gently until completely dissolved (this may take a few minutes, so be patient). Determine the mass of the. Determine its volume. Determine the mass of 10.0 ml of your sugar-water. Determine the mass of 15.0 ml of your sugar-water. Determine the mass of 20.0 ml of your sugar-water. Determine the mass of 35.0 ml of your sugar-water. Repeat this entire process using 25.0 g of sugar and 15.0 g of water. AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 4 of 7

5 Download Data Sheet Data Sheet Name Part 1. Volumetric Measurements ¼ cup = ml 6 tablespoons = ml cups = ml ½ cup = ml teaspoons = 10.0 ml Part 2. Mixture of Two Solids Volume of large grained solid Density of large grained solid Volume of small grained solid Density of small grained solid Volume of mixture of solids Mass of mixture of solids Density of mixture of solids Were the masses additive? (I.e. did the masses of each of the solids add up to the mass of the mixture?) Were the volumes additive? (I.e. did the volumes of each of the solids add up to the volume of the mixture?) Part 3. 1 st Solution of sugar and water Volume of 20.0 g of sugar Density of 20.0 g of sugar Volume of 20.0 g of water Density of 20.0 g of water Volume of 1 st sugar-water Mass of 1 st sugar-water Density of total 1 st sugar-water AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 5 of 7

6 Volume of 1 st sugarwater Mass of sugarwater Density of sugarwater 10.0 ml 15.0 ml 20.0 ml 35.0 ml 2 nd Sugar-Water Solution Volume of 25.0 g of sugar Density of 25.0 g of sugar Volume of 15.0 g of water Density of 15.0 g of water Volume of 2 nd sugar-water Mass of 2 nd sugar-water Density of total 2 nd sugar-water Volume of 1 st sugarwater Mass of sugarwater Density of sugarwater 10.0 ml 15.0 ml 20.0 ml 35.0 ml AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 6 of 7

7 Answer the following questions. 1. When you mix two substances together are the volumes additive? Use your experimental evidence to support your answer. 2. When you mix two substances together are the masses additive? Use your experimental evidence to support your answer. 3. Use results from your experiment to demonstrate that density is an intrinsic property. AACE Copyright 2000 by Doris Kimbrough, all rights reserved Page 7 of 7