Density Notes
Science
Notes on density
Notes on density. In order to calculate density, you need to make two measurements. The first would be mass, mass tells us the amount of matter in a given object. The metric unit for mass is grams. Mass is measured using a balance. We have triple beam balances, double pain balances, and more commonly used today are digital balances. Before you measure the mass of an object, you should zero the balance on a digital balance. This will be a button labeled tear. And pressing the tear button will balance the scale back to zeros. Volume is the amount of space an object takes up to measure the volume of a liquid.
You use a graduated cylinder as seen in the picture. And the metric unit for volume of a liquid is liter and the smaller unit would be milliliters. For the volume of a regular solid that you can measure the even sides on, you would measure length width and height and multiply these three measurements to get the volume. If you were measuring length width and height in centimeters, your unit for volume would be centimeters cubed because you've multiplied centimeters times centimeters times centimeters. So volume of a regular solid, the units would be centimeters cubed. For an irregular solid, for instance, a rock sample, if you can't measure length width and height, you can use the process of water displacement. So you would put water in the graduated cylinder, record the beginning volume, reading from the bottom of the meniscus. Then you would place the object into the water, make sure that the object is completely submerged and record the new volume.
When you subtract these two volumes, you would get the volume of your object. Again, this method is called water displacement. The metric unit for volume of a solid is centimeters cubed. So if you use water displacement method to measure a solid, you should report your units in centimeters cubed. So other scientists know you're referring to a solid object, even though you use milliliters. So a centimeter cubed is the exact same amount of space as 1 mL. So density is a combination of these two. It's the amount of matter in a given space. The formula for finding density is mass divided by volume. So we keep the units that we'd use for mass and the units we use for volume. Therefore, units for a solid would be grams per centimeter cubed and density units for liquid would be grams per milliliter. We see examples of density in our everyday lives. For instance, in this picture, the ice is floating because it is less dense than water. Hot air balloons rise because the air inside them gets heated, warm air is less dense than the air around it. So it causes the balloon to rise.
Helium balloons rise because helium is less dense than the mixture of mostly nitrogen and oxygen in the air. And oil floats in water because it is less dense than the water. So things that float or sink are happening because there are differences in densities. In Earth science, we will study density in all of the branches of earth science. For instance, air is constantly in motion because warm less dense air rises and cool air sinks. This creates sea breezes as seen in the picture. In the oceans, cool water sinks because it is more dense and warm water rises and travels through the ocean. So this creates a global conveyor belt of ocean water.