Density

Density

Hillary Clark 10/6/17 P4

What is Density?

 Have you ever wondered why water and oil don’t mix? The oil always floats to the top, and density is the reason why. Because oil is less dense than water, they will not mix. Density is the ratio of the mass of an object to its volume. In other words, density is the amount of stuff (atoms,molecules,etc.) in a fraction of matter.

 

How to Find Density

                                      

 To find the density of an object, you first need to know the things mass and volume.Then, you divide the object’s mass by its volume to find the density. Mass is measured in grams (g), and volume is measured in cubic centimeters (cc), or centimeters cubed (cm3) . When you find the density after dividing, you must label your answer with ‘g/cc’ or ‘g/cm3’ after your answer.                                https://drive.google.com/open?id=0B0CyJqI5OQFUNW94NGtwbHJTX05Kd2p4dU9vMjFpaVVEMXhF

 The necessary tools needed to find density are a scale or balance (triple beam balance, electronic balance) to find the mass, a graduated cylinder to find the volume of a liquid (you can also use measuring cups or a hydrometer.) and the volume of irregularly shaped solids. The volume of a gas varies on its container, considering gases expand to fill whatever space possible. To find the volume of a regularly shaped solid, you can calculate it by its dimensions. You can use a ruler to measure the dimensions than solve. For example, the volume of a rectangle is its length x its width x its height. So if a rectangle has a length of 6, a width of 2, and a height of 4, the volume would be 48 cc. The volume of an irregularly shaped solid can be found using the displacement method. The displacement method is as follows:                                                      Example:

                                    Before: 30 mL After: 40(40-30=10) V=10mL                                

        For Smaller objects

Step 1	Get a graduated cylinder and fill to a known  volume with water.
Step 2	Place the object into the cylinder.
Step 3	The volume of the object is equal to the change in water level.

                                                                                                           

 For larger objects               

Step 1	Use a displacement can & put a graduated cylinder under the sprout.
Step 2	Fill displacement can with water until some overflows.
Step 3	Empty graduated cylinder.
Step 4	Place the object into displacement can.
Step 5	The volume of water in the graduated cylinder= volume of object.

Once you find the mass and volume : Use a calculator and divide the object’s mass by its volume and the result is the object’s density.

Sample Density Problem

1. A graduated cylinder was filled to 42 mL. with water. When a  screw was placed into the graduated cylinder, the water rose to 54 mL. The mass of the screw is 9 ⅓ grams. What is the density of the screw ?

              

First, you have to find the volume. Using the displacement method, since the screw is an irregularly shaped solid. You subtract 54 and 42 to get 12, and then go on to find the density. With a mass of 9.33 or 9 ⅓ and a volume of 12, you will get a density of about 1.3 g/mL after dividing.

2. A cube has a length, width, and height of 7 cm. The mass of the cube is 8.6 grams. What is the  density of the screw?

   Once again, you’re going to have to find the volume. Because the cube is a regularly shaped object, we will not be using the displacement method. To find the volume, you simply use the formula for finding the volume of a cube, length x width x height. The length, width , and height are all 7, and 7 cubed is 343. Then you will repeat the density formula, dividing the mass (8.6 g) by the volume (343 cc). When you divide them, you will find the density, which in this case is about .025 g/cc.

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