Density
Density Density: a measure of how tightly packed the molecules in an object are
Density is a measure of how much “stuff” is packed into a space Think about these suitcases One is filled with 1000 pairs of socks The other is filled with 100 pairs of socks Which one is more dense??
Density Density depends on mass and volume
Similar Shapes and Density Which one of these has the lowest density? A balloon A bowling ball A basketball A volleyball
Similar Shapes and Density Which one of these has the highest density? A balloon A bowling ball A basketball A volleyball
Similar Shapes and Density Objects of the same volume can have very different densities
Some Things Float…. Some Things Sink… A granite rock is more dense than water so it sinks Certain woods are less dense than water so they float Materials that are less dense than water float Materials that are more dense than water sink
Anyone recognize this?
It’s the “unsinkable” Titanic titanic clip
Dialogue from the movie Titanic… Dialogue from the movie Titanic….the engineer knows the density of iron and says that sinking is a certainty.
Some things float… Some things sink… It was mathematical possible for the Titanic to sink because it was made of iron and iron is more dense than water.
The Density of Water Water is very unique because it is less dense in its frozen state, than it is in its liquid state. This is why ice floats.
Density Equation d = density m = mass V = volume Density is measured in g/mL or g/cm³
Finding mass and volume How do I find mass using the density equation? m = dV Mass is measured in grams How do I find volume using the density equation? V = m/d Volume is measured in mL or cm³
Find the volume (L) ___ x (W) ____ x (H)____ = (V) ___
How do we find the volume of this??
archimedes A Famous Story about Archimedes: King Heiro suspected the royal goldsmith had created an inferior gold wreath crown by mixing gold with silver. He ordered Archimedes to find a way to prove the wreath was or was not pure gold.
Archimedes knew the density of pure gold and the density of pure silver. If the density of the crown was 1.3 lbs per fluid oz, he would know it’s pure gold, but if it’s less than that, then it was mixed with the less dense silver. He could weigh the crown but could not find its density because he couldn’t measure its volume because of its irregular shape. He didn’t dare melt it down. He struggled with this problem for a long time until he came up with a plan while getting into a bath tub.
Eureka!: As he got into the tub, he saw the water rise. He suddenly realized the volume of his body was displacing the water, causing the water level to rise by the same volume of his body. He yelled “Eureka!” meaning “I found it!” (he had found the answer to testing the crown). He ran down the street naked yelling “Eureka!” Two thousand years later, prospectors for gold would yell, “Eureka!” when they found gold, not knowing that the word is Greek and made famous by Archimedes
How to measure volume of irregular object: Before lowering the crown into the water, the level of the water is marked. The crown is lowered into the water and the water level will rise. The new level is marked and the volume difference of the water is the volume of the crown. So if the weight was 3.3 lbs and the volume increase was 3.3 fluid ounces, what is the density? 3.3 lbs = 1 lb. 3.3 fl.oz fl.oz. Is it pure gold? No, because pure gold is 1.3 lb/oz.
Finding Volume For an object with uneven, hard to measure surfaces, use displacement: The difference in water level in a graduated cylinder after the object is added to the water
Water Meniscus Meniscus: the curved upper surface of a liquid in a tube When measuring liquid, measure at the bottom of the meniscus at eye level
What is the volume of water in the graduated cylinder?