DENSITY
DENSITY=MASS/VOLUME What is Density? Density is the ratio of mass to volume of an object. The density of a material is determined by the mass and arrangement of its atoms DENSITY=MASS/VOLUME
First Things First…Mass In order to calculate the density of an object, you first must calculate its mass. But what is mass? The amount of matter that makes up an object Is mass the same thing as weight?
No. Mass is not the same thing as weight No! Mass is not the same thing as weight. Weight is a measure of the force of gravity on an object. However-mass is proportional to weight. In this class, we find the mass using a triple beam balance http://www.youtube.com/watch?v=BAf6HoVK6JI
Next Things Next…Volume After you find the mass of the object, you must find its volume. What is volume? Volume is the amount of space an object occupies How do we find the volume? There are two ways you can find volume…
How do we find the volume? Volume of a solid is measure in the unit grams per centimeters cubed (g/cm^3) When finding the volume of a regularly shaped object, simply use the appropriate equation! Cube/Rectangular Prism: Length x Width x Height Cylinder: Pi x Radius^2 x Height Sphere: 4/3 x Pi x Radius^3 Cone: 1/3 x Pi x Radius^2 x Height You don’t have to memorize these!
How do we find the volume? Another way to find volume is the water displacement method. This method uses the fact that a submerged object will displace a volume of liquid equal to its own volume. This method is most useful when the object you are measuring has an irregular shape. http://www.youtube.com/watch?v=RoKCwl3echA
Sink Or Float? The density of water is 1gm/cm^3. Any object with a higher density will sink in water. An object with a lower density will float in water!
Sink or Float? If an object has a density of 10g/cm^3 will it sink or float? Sink!
Densities of Liquids The density of a liquid is measure in the unit grams per milliliter (g/mL) To find the density of a liquid, follow the same steps you take to find the density of a solid Finding the volume of a liquid is easier than a solid, but to find the mass takes on extra step!
Mass of a Liquid To find the mass of a liquid, you will use a triple beam balance, but since you can’t just set the liquid on the balance without making a big mess, you have to put it in a container first. If you simply set the container on the balance and take the mass, you are also getting the mass of the container- SO: Take the mass of the EMPTY container Take the mass of the container with the liquid inside Subtract the mass of the container from the total mass to find the mass of the liquid only!
Volume of a Liquid Finding the volume of a liquid is easy! Just pour into graduated cylinder and read what number the liquid comes up to!
Liquid Densities When liquids with different densities are placed in the same container, will the more dense liquid or the less dense liquid float to the top? The less dense will float! Which is more dense, vegetable oil or water? Water!
Practice! Find the density of an object that has a volume of 15cm^3 and a mass of 30g. Density=Mass/Volume Density=30g/15cm^3 Density=2g/cm^3 (DON’T FORGET YOUR UNITS!!)
Practice Find the density: A liquid has a volume of 20mL. The mass of the graduated cylinder is 50g. The mass of the graduated cylinder with the liquid in it is 90g. Mass of the liquid= Mass of the cylinder with liquid – mass of cylinder 90g-50g=40g Density = Mass/Volume 40g/20mL= 2g/mL