The relationship between mass, volume and density.? | Yahoo Answers
density equals mass divided through volume. When some material is denser than another it sinks in it - steel is denser than water, but water. Density is the mass of an object divided by its volume. You probably have an intuitive feeling for density in the materials you use often. and one with a density of g/cm3, the rock will have a density between and Density is defined as mass per unit volume. d = mV. Example: A brick of salt measuring cm x cm x cm has a mass of g.
In the case of gases, the reference material is standard dry air, or air without water. In the case of liquids and solids, the reference material is fresh water. Specific gravity is calculated by dividing the density of a substance by the reference substance's density.
For example, gold has a density of This yields a specific gravity of This means gold is Buoyancy Whether an object floats or sinks is determined by the downward force of gravity and an upward buoyant force. If the buoyant force is greater, an object floats.
How are density mass and volume related?
If the force of gravity is greater an object sinks. The interplay between these forces is related to the density of the object and the density of the fluid it is placed in. If the overall density of the object is greater than the liquid, the object sinks. Inertial mass measures how strongly an object resists acceleration, while gravitational mass measures how strongly an object attracts other things to itself.
Strictly speaking, a scale measures weight, but you can usually think of weight and mass as the same thing. Space and Volume Volume measures the spatial size of an object. Although the formula used to calculate volume depends on its shape and can be complicated, you can think of it generally as width times height times length.
Density – a relationship of mass and volume -
Measuring an object's volume can sometimes be easier than calculating it. Putting it into a large container of water and measuring the rise in water level can quickly find the volume, no matter what shape it is.
Density is sometimes used to describe other quantities divided by volume, such as energy density. The densities of thousands of substances, including metals, plastics and more, are well-known. Probably time could be saved in class if the necessary strings were cut to length in advance and perhaps even tied to the cups.
Building the "Weight Scale" requires some careful cutting of a straw that can be done with a good pair of scissors or a sharp knife. We think kids can do all of it but it will take time.
You should build one prototype Weight Scale in advance so you can work out the details of construction and decide how much of the cutting should be done in advance. Teaching outline and Presentation suggestions: Once again we remind you that we really don't know the best way to teach these concepts to young students.
The following are suggestions for construction and use of the equipment and how we envisioned one might use this stuff but only you can know the best way to present this material to your students. Mass is usually measured with a balance. The idea is to compare the unknown object with the mass of a known amount. Illustrated below is the device we will use to measure mass and we will call it "the Mass Balance".
Since everyone seems to have lots of pennies and all pennies are about the same mass, we will use the penny as our standard of mass. It turns out that the average penny has a mass of about 2.
The mass measurement is accomplished simply by placing the unknown object in one cup of the Mass Balance and finding out how many pennies placed on the other side it takes to achieve balance. You should first check the Mass Balance with nothing in either cup to see if it is properly "zeroed".
You should notice that the balance is most sensitive when the upper paper clip is in the center hole in fact it is really too sensitive here and it will be less sensitive when you use the higher holes.
Slight errors in the zero reading can be corrected by using shorter or longer string sections on the appropriate side. Make sure all paper clips rotate freely in the drilled holes. The balance will not work properly if the paper clips hang up. The Mass Balance can be loaded with the cups on the table and pulling upward slightly on the support paper clip will test the balance condition. We suggest that students begin by matching pennies on the left with pennies on the right and they should discover that all pennies aren't really the same--this is real!
The Relationship Between Mass, Volume & Density | Sciencing
After the students become familiar with the use of the balance, we suggest that nearly equal volumes of the assorted materials sand, rice, metal shot, Styrofoam be measured.
If you are using the 1 oz Dixie portion cups, it is possible to draw a line on the cup 1. A very important question to consider now is: If you used this Mass Balance on the moon or on Mars, would the same amount of material on one side require the same number of pennies on the other side to balance it as it did on Earth? Naturally there is no easy way for us to perform such an experiment but, having your students think about this should help them to start understanding the difference between weight and mass.
Density – a relationship of mass and volume
Mass or as Newton would say, the quantity of matter in an object, does not change when you change your location in space but, as we will see shortly, weight does change. Using a carefully segmented straw, a bent paper clip, a rubber band, some string, a small cup, a 3X5 card and some scotch tape we will construct the "Weight Scale" shown below: Since we had difficulty in joining the segment of rubber band to the string, we decided to show you a "carrick bend" which works quite well for this situation.
A simple slip knot works well on the bottom where the rubber band attaches to the bent paper clip bail. A later construction detail diagram will give you a better illustration of the Weight Scale. The students will calibrate this Weight Scale with pennies and mark the 3 X 5 card with a marking pen during the calibration exercise.
Attaching the rubber band to the bail of the cup is easily accomplished with a slip knot but attaching the string to the rubber band is a slight problem--a suggested knot is shown with the illustration. The whole idea is to have the zero of the scale at the bottom of the card using the string-rubber band junction as the pointer.Density Practice Problems
With about 25 pennies in the cup, the rubber band will stretch to about the top of the card. You hold the scale with the string which has been passed through a small piece of straw taped to the card. The students will carefully load the cup with pennies and mark the card at about 5 penny intervals. A more detailed construction of the Weight Scale is shown "below. Note that in the construction diagram "below", we show how the straw should be sectioned so that it can be attached to the 3 X 5 card.
In the final scale, naturally, the string and rubber band fit inside of the straw sections. It is important that the lower length of the straw be made just long enough to extend from the top of the paper clip "bail" to the bottom of the card with the rubber band sticking out the top.
You must be able to tie the rubber band to the string and have the junction of the two be on the lower end of the 3 X 5 with nothing in the cup. This is the "below" referred to in the above paragraph.
We decided it would take a large image to show the necessary details so, if you have the time, click here for Weight Scale Construction Details. After the students have calibrated the Weight Scale, it might be fun to have them see if they can guess how many pennies have been loaded into their cup by another student. From this they will learn how to read between the marks they have placed on their cards this is called interpolation and they will also learn that the scale is really not too accurate.
However, all instruments are less than perfect at some level and this crude scale should help them to realize this fact. We think it is nice that the scale is quite inexpensive and students who wish can construct one at home. This Weight Scale can also be used to measure some of the other materials that were measured with the Mass Balance.
Hopefully they will find that they will get pretty close to the same answer in "pennies" for the mass as measured on the Mass Balance and the weight as measured on the Weight Scale.
So you ask--what is the difference between weight and mass? Now comes the key question to ask the class: If you took the Mass Balance and your calibrated Weight Scale to the Moon, do you think they would give the same measurement as on Earth?
Remember, you always balance the unknown object against several pennies with the Mass Balance but you just let the unknown object pull down against the calibrated rubber band on the Weight Scale. We hope that this thought experiment will help the students see that the Mass Balance will measure the same no matter where you locate it in space but the Weight Scale, which measures how hard gravity pulls down on the object, will give a smaller reading on the moon.
This is confusing stuff and most college students will have difficulty understanding it. Perhaps if your kids start thinking about it early enough, they may come to a better understanding of the difference between weight and mass when they are older. Since density is mass per volume, the most straight forward way of measuring the density of something is to measure its mass, then measure its volume and divide the mass by the volume.
We could do exactly that in this activity but at this point we have no good way to measure volume.
If you have a graduated cylinder they aren't expensive but most elementary schools don't have them you could use it with some water to mark the small "portion cups" at specific volumes. We have already suggested that the small 1 oz cups will hold 10 cubic centimeters when filled to a point 1.
Rather than actually measuring the density, we feel it will be sufficient for the students to appreciate that the same volume can be a large mass or a small mass depending upon the material involved. Our plan is to have the same volume of several different materials and measure their mass with the Mass Balance.
Hopefully this exercise will help the students to begin to see the relationship between mass, volume and density.