Properties of MatterMore properties of liquids

Properties of Matter•Less dense floats on more dense

–Water density is 1 gram per mL

–Cooking oil density is .9 gram per mL

–Oil floats on water

Properties of Matter•Buoyancy pushes up–A rock in water weighs less than a rock on dry land

•Same mass, but the water pushes the rock up, making it feel less heavy, like two people carrying something heavy make it easier to carry•Rock has more mass than the water can push up, so it sinks—it is more dense than the water

Properties of Matter• Buoyancy pushes up– Steel has a density of almost 8 grams

per mL

–Water has a density of 1 gram per mL

– The buoyancy of water cannot overcome the density of steel, so steel sinks

– How do steel ships float?

Properties of Matter•Buoyancy pushes up

–Steel in the ship has been reshaped so there is a lot of air inside (cabins). The density is much less because of the bigger shape (volume).

–Ships float because their density is made so much smaller that their greatly increased volume would displace (push aside) more water than the ship weighs.

–When the ship can displace more water than it weighs, it cannot overcome the buoyancy force pushing it up, so it floats instead of sinks.

Properties of Matter•Buoyancy pushes up–Just like a car’s metal is stretched and the car is mostly air now:

http://www.filmtrix.com/movies/crush.mov

–A ship’s metal is stretched even more and if you crushed a ship it would contain a very tiny portion of the volume it used to, so the density would increase.

Properties of Matter• Buoyancy pushes up– Remember the glass bead sank in the

water in the graduated cylinder• It pushed water out of it’s way because

water and the bead cannot occupy the same space• Some beads displaced 1 mL of water, which

weighs 1 gram• The beads weighed more than 1 gram and

their density was more than 1 gram/mL, so they sank• If the beads pushed more water away than

they weighed, they would float• How could we make a glass bead float?

Properties of Matter•Buoyancy pushes up–How would we make a glass bead float?

–Reshape it so it’s volume would increase until it would push more water away than it weighs (if the bead weighed 2 grams, it would have to push more than 2 grams of water aside).

Properties of Matter• Not all liquids have the same

buoyancy force

– Remember the rock we talked about weighing less in water. In another liquid, it might have a different weight.

– Every liquid has it’s own buoyancy force

Properties of Matter• Do you think it’s possible to create a

concrete object that floats? State your hypothesis on your worksheet.

(hint: the density of concrete is 2.3 grams/mL compared to steel, which has a density of about 8 grams/mL)