Weather Density of Liquids and Solids How much of the country depends on snowfall for the year’s water supply? The mountains get many feet of snow every

Weather Density of Liquids and Solids

• How much of the country depends on snowfall for the year’s water supply?

• The mountains get many feet of snow every winter, and then, as temperatures rise in the spring, it melts.

Weather, L 3, Density of Liquids and Solids

• Can scientists measure the snowpack and then predict the amount of water that will be available for consumption the rest of the year?

• How much water is present in equal volumes of snow and rain?


• To answer this question we will look at:

- density and phase- converting snowfall to rainfall- the density of ice


• Scientists measure the snowpack, or total amount of snow to predict the amount of water that will be available later in the year.• These scientists are more interested

in how much liquid water the snow represents.


• When snow melts, its volume decreases, but the mass remains the same. Volume=the amt of space an object takes up.• Density = mass ÷ volume, or

• D= M / V

• The density of snow is __<__ than water


Snow WaterMass is not lost, but volume changes.


• Unlike water, snow has a wide range of densities.• Snow can be fluffy or it can be

packed.• As long as the density of the

substance doesn’t change, its mass and volume are proportional.


• The proportionality constant here is the density, D.

mass = D x V• When we graph the mass versus

volume for water, snow, and rain, the data points lie on a straight line that passes through the origin. (0,0)


Volume (mL)

What do the slopes of these three lines show us?


• Matter changes density when it changes phase. • One way to determine the volume of

water in the snowpack is to melt it.• This isn’t practical, so scientists take

samples of new snowfall then determine the density (divide mass by volume.



• After pushing the empty aluminum tube into the snowpack, the tube is weighed.• The density of the snow is the mass

divided by the volume.Lets look at an example.


msnow = Dsnow x Vsnow

• Suppose you have 20 mL of snow with a density of 0.25 g/mL• What volume of liquid water will you

get when you melt this amount of snow?• When snow melts the mass will not

change, so


• Msnow = Dsnow x Vsnow and so

• msnow= (0.25 g/mL) x (20 mL) = 5 g

• You can also solve this problem using a graph. The graph shows mass versus volume for liquid water.


Converting Snow to Liquid Water

Volume (mL)

Water


• Begin with 20 mL of snow, which is equal to 5 g of water.• When snow melts, the mass remains

the same, and 5 g of water is equal to 5 mL of snow.

The Density of Ice• The density of ice is 0.92 g/mL. It is

less dense than water (1.0 g/mL).


• When water freezes it becomes less dense, and its volume decreases.• This unique property of water is due

to a special kind of intermolecular force called hydrogen bonding.• When water freezes, the molecular

motion slows down, and molecules lock into a hexagonal structure due to hydrogen bonding.


Work this out!!

• Mass=DxV Density=M/V Volume=M/D

• 2 samples of water. Each in a different phase.• Liquid = 20 mL (density is 1.0 g/mL) mass=_______

• Ice = 40 mL (density is .92 g/mL)• mass=________• One is less dense than the other and will float on the

other. Which one?• One has more volume than the other. Which one and

why?

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Weather Density of Liquids and Solids How much of the country depends on snowfall for the year’s water supply? The mountains get many feet of snow every