Formula & Units
What's the formula for density?
Density = Mass ÷ Volume
What piece of equipment is used to measure liquid volume?
Graduated cylinder
Why does ice float on water?
Ice is less dense than liquid water.
A block has mass 50 g and volume 25 cm³. What is its density?
2 g/cm³.
True or False: A small object always has less density than a large one.
False
What is the SI unit of density? (both)
kg/m³ or g/cm³
What equipment would we use to measure the mass of an object?
Mass balance
Why does a ship made of steel float?
Its overall density (hull + air inside) is less than water.
A liquid has mass 120 g and volume 150 cm³. Find its density.
0.8 g/cm³.
Which is denser: Eugene's school bus filled with students or empty?
Filled with students (more mass, same volume).
Rearrange the density formula to find volume.
Rearrange the density formula to find volume.
Why measure an empty graduated cylinder before liquid density? (And no, “because Ms. Lehane said so” is not the answer).
To subtract the cylinder’s mass and find the mass of the liquid.
If an object has a lower density than the substance it is in, it will _______
Float
A block of metal has density 7.8 g/cm³ and volume 15 cm³. What is its mass?
117g
A silage bale weighs 670 kg. If its volume is 10 m³, what’s its density?
67 kg/m³.
What are the units of volume?
m3 or cm3
What is the main source of error when measuring volume by displacement?
Reading the meniscus incorrectly
If an object has a greater density than the substance it is in, it will _______
Sink
A block of wood has a mass of 200 g. Its length is 10 cm, width 4 cm, and height 2.5 cm. Calculate its density.
Volume = 100 cm³; Density = 2 g/cm³.
Why did the Titanic sink after hitting the iceberg?
Density changes - became higher than water.
What is the formula for volume?
L X W X H
What is the definition of density?
Density is how tightly packed atoms are in an object.
What two things do we need to calculate density?
mass and volume.
A cube has sides of 4 cm and a mass of 128 g. What is its density?
Volume = 64 cm³, Density = 2 g/cm³.
Ms. Lehane drops her phone (mass = 200 g, volume = 50 cm³) in a tank of milk (density = 1.03 g/cm³). Does it sink or float?
Sinks (density = 4 g/cm³ > 1.03 g/cm³).