Substances and Their Shape

8/4/2019 Substances and Their Shape

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States of Substance


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States of substances

According to their states, substance were

grouped into 3 parts.

Shape of Substances Shape characteristic Volume characteristic

Solid Its shape is permanent Permanent

Liquid Its shape is always changing,

following its container

Permanent

Gas Its shape is always changing,

following and filling its

container

Changing


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Change of state of substance

Solid

LiquidGas

condensing

steaming


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From the diagram before, the conclusions are:

Melting is the state changing from solid to liquid

F

reezing is the state changing from liquid to solid Steaming is the state changing from liquid to gas

Condensing is the state changing from gas to

liquid

Crystallizing is the state changing from gas to solid

Sublimating is the state changing from solid to gas


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Molecule and particle

Molecule is the smallest division (of object)

having same characteristics as the original

substance.

Molecule formed by another smaller particle

called atom.

Two or more atoms merged would forming

molecule. Molecular theory or atomical theory can be used

to explained the change of state of substance.


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Solid having permanent shape because of itsclosed-each other and well-regulated molecules.It causes the molecule of solid is hard toseparated. The movements of molecules of solidare only vibrating and rotating on their place.

Liquid having changed state and always adapt toits container, but its movements are more freethan the movement of solid. The molecules of

liquid could easily moving, but hardly leavingtheir group because there is any pull forcebetween them.


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Gas having changed shape and volume because

of its molecule can freely moving. The space

between the molecules is farer than the size of

the molecules, so the pull force is very weak.

solid liquid gas


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Differentiating cohesion and adhesion

Cohesion is a pull force between the particles

of the same substance.

Adhesion is a pull force between the particlesof the different substance.

Example:

Water wetting the glass and shaping wide because

of the cohesion inter-water molecules is bigger

than the adhesion between the water molecules

and the glass molecules.


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Meniscuses (concave and convex)

Cohesion and adhesion are influencing thesurface shape of liquid in its container.

Concave

meniscus

Convex

meniscus


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The surface shape of liquid in the react tube thatformed concave is called concave meniscus. Thishappened because of the cohesion inter-water

molecules is smaller than the adhesion of thewater molecules and the glass molecules.

The surface shape of liquid in the react tube thatformed convex is called convex meniscus. This

happened because of the cohesion inter-mercurymolecules is bigger than the adhesion of themercury molecules and the glass molecules.


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Concave meniscus and convex meniscus are

causing different contact angle between the

area of container (tube) with the surface of

liquid.

Concave meniscus causes an acute (90 )


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Capillarity

Capillarity is the tendency of liquid rise or set inthe capillary tube or small tube.

Cohesion and adhesion are influencing the

capillarity tendency. When a glass capillary tube is half-dyed in water,

the water will rise in the glass vessel of thecapillary tube.

When a glass capillary tube is half-dyed inmercury, the mercury will set in the glass vesselof the capillary tube.


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Water Water in

capillary

tube

Mercury Mercury in

capillary

tube


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Examples of natural capillarity tendency:

In some plants, their tip root can rise up to the

leaves

The gasoline rise up to the wicks of stove

The inner wall in some house will wet when the

rain comes (when the outer wall contacted with

the raindrop, it will wet, and it can be seep to theinner wall of the house)

Substances and Their Shape

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