Ask a question: What is happening? Why?

Why do these float?

Density

What is density? Density is a ratio of how much matter there is in a certain amount of space. Density is a ratio of how much matter there is in a certain amount of space. A measure of how many particles are packed into a certain area. A measure of how many particles are packed into a certain area.

More dense = more particles in a space Less dense = less particles in a space

How do I find density? I need to find out how much stuff (mass) is in a certain amount of space (volume) I need to find out how much stuff (mass) is in a certain amount of space (volume)

What instruments do I need? To find the mass of an object To find the mass of an object Triple Beam Balance Triple Beam Balance Units are g Units are g To find the volume of the object To find the volume of the object Ruler or graduated cylinder Units are cm 3 or mL

How do I calculate density? Density = mass OR mass ÷ volume. Density = mass OR mass ÷ volume. volume volume Units for density: g or g Units for density: g or g cm 3 m l cm 3 m l ALWAYS REMEMBER UNITS!

Does the sample size affect the density of an object? In other words, if I break off a piece of this cube, will it have a different density than the whole piece? In other words, if I break off a piece of this cube, will it have a different density than the whole piece? NO!!! NO!!!

Density is based on total mass divided by total volume. When one changes, the other also changes, so the density (which is a ratio) stays the same!!!

Which one is more dense? Which table group is most dense in the classroom? Which table group is most dense in the classroom? How about this: Which square is more dense? How about this: Which square is more dense?

Density of Water Water has a density of 1g/mL Water has a density of 1g/mL If an object has a density greater than 1g/mL, it will sink in water If an object has a density greater than 1g/mL, it will sink in water If an object has a density of less than 1g/mL, it will float in water. If an object has a density of less than 1g/mL, it will float in water.

What do we know about the density of diet coke vs. coke vs. water?

Do liquids have different densities? Yes! So what happens when you mix them? Yes! So what happens when you mix them? They form layers with the highest density falling to the bottom. They form layers with the highest density falling to the bottom. Alcohol =.80 g/ml Alcohol =.80 g/ml Vegetable Oil =.90 g/ml Vegetable Oil =.90 g/ml Water = 1.0 g/ml Water = 1.0 g/ml Salt Water = 1.2 g/ml Salt Water = 1.2 g/ml

The density of the liquid affects how you float too! Denser liquids help you float more easily. Denser liquids help you float more easily. That is why it is easier to float in the ocean, than in a freshwater lake. That is why it is easier to float in the ocean, than in a freshwater lake.

Illustrating Density

Metals have different densities Lead 11.3 g/cm 3 Lead 11.3 g/cm 3 Aluminum 2.7 g/cm 3 Aluminum 2.7 g/cm 3 These are all over 1.0 g/ml and most ships are made of metal. So how do boats float? These are all over 1.0 g/ml and most ships are made of metal. So how do boats float?

Explain why one bowling ball floats and one sinks

Density affects many of Earth’s processes

Density helps create ocean currents

Density helps move melted rocks under Earth’s crust Hot material rises, cooler material sinks, creating a current, called a Convection Current Hot material rises, cooler material sinks, creating a current, called a Convection Current core mantle crust

Solid Land has different densities Continental Plates – lighter, thicker, made of granite Continental Plates – lighter, thicker, made of granite Oceanic Plates – heavier, thinner, made of basalt Oceanic Plates – heavier, thinner, made of basalt

Convergent Boundary Plates move toward each other Plates move toward each other The more dense oceanic plate subducts under the less dense continental plate

Normal and Low bone densities Low density bones break more easily. Low density bones break more easily.

Temperature can affect density Remember... Warm air rises. Remember... Warm air rises. So this means warm air is less dense than cold air and it rises So this means warm air is less dense than cold air and it rises

Density causes your attic to be hot in the summer