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Words You Should Know
Melt – when a solid changes to a liquid
Freeze – when a liquid changes to a solid
Solidify – a liquid changes to a solid
Dissolve – when a solid ‘disappears’ in a liquid
Solution – a liquid with a solid dissolved in it
Undissolved – when a solid doesn’t disappear
Filter – a way of getting undissolved solids out of a liquid.
Here’s some questions for you to answer:
Are all liquids colourless?
What will happen to a liquid if the container it is in changed?
Can you spill solids?
What happens if you tilt the bottle that a liquid is in?
The egg timer below is full of sand. The sand falls from one end to the other and is used to measure units of time.
Many materials can exist as a solid or a liquid. When it changes from a solid to a liquid we say it melts.When it chnges from a liquid to a solid we say it freezes.
Melting and solidifying or freezing are chages that can be reversedand are the revers of each other.
Did you know solids can be seperated? We could do this for example by using a sieve.
Solids And Liquids
Solids, liquids and gases are the three states of matter. All matter is made from small particles. These particles are called atoms and molecules.
The things that you need to know about solids, liquids and gases (in order of difficulty) are:
Firstly, let us deal with the general properties of the three states of matter.
- Solids:
They keep their shape unless they are broken
- They do not flow
- They cannot be compressed (keep the same volume)
- Liquids:
They do not keep their shape, they take the shape of the container they are in
- They flow
- They cannot be compressed (keep the same volume)
Secondly, let us deal with the uses of solids and liquids.
Solids:
Solids are used where we need something to keep its shape or to support something. This is because they keep their shape, stay where they are put and cannot be compressed.
Imagine a chair. Try to imagine what it would be like if the chair was made from a liquid. Would it keep its shape? Would it support your weight? Would it stay where you put it?
Now, think why bike frames, scaffolding poles and motor vehicle bodies are made from solids.
Liquids:
Liquids are used where we need something to flow e.g. for making a drink, or when we need something to take up the shape of a container such as a mould. A good example of this is making a jelly. The jelly (solid) has to be turned into a liquid (in this case by dissolving) so that it takes up the shape of the mould. It is then left to set (i.e. go solid again) so that it keeps its shape when removed from the mould.
Now think why swimming pools are filled with water and why shampoo and shower gel are liquids.
What Is A Solid?
Some solids consist of very small pieces like sand, they are sometimes called powders. They behave in similar ways to liquids.
A solid object is in the states of matter characterized by resistance to deformation and changes of volume. At the microscopic scale, a solid has these properties: The atoms or molecules that comprise the solid are packed closely together. These constituent elements have fixed positions in space relative to each other. This accounts for the solid's rigidity.
In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice. The spacing between unit cells in various directions is called its lattice parameters. The symmetry properties of the crystal are embodied in its space group. A crystal's structure and symmetry lay a role in determining many of its properties, such as cleavage, electronic band structure, and optical properties.
If sufficient force is applied, either of these properties can be disrupted, causing permanent eformation. Because any solid has some
thermal energy, its atoms vibrate. However, this movement is very small, and cannot be observed or felt under ordinary conditions.
What Is A Liquid?
A liquid's shape is confined to, not determined by, the container it fills. That is to say, liquid particles (normally molecules or clusters of molecules) are free to move within the volume, but they form a discrete surface that may not necessarily be the same as the vessel. The same cannot be said about a gas; it can also be considered a fluid, but it must conform to the shape of the container entirely.
At a temperature below the boiling point, a liquid will evaporate until, if in a closed container, the concentration of the vapors belonging to the liquid reach an equilibrium partial pressure in the gas. Therefore no liquid can exist permanently in a complete vacuum. The surface of the liquid behaves as
an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. Capillarity is another consequence of surface tension.
Only liquids can display immiscibility. The most familiar mixture of two immiscible liquids in everyday life are the vegetable oil and water in Italian salad dressing. A familiar set of miscible liquids are water and alcohol. Only liquids display wetting properties. Liquids at their respective boiling point change to gases (except when superheating occurs), and at their freezing points, change to solids (except when supercooling occurs). Even below the boiling point liquid evaporates on the surface. Objects immersed in liquids are subject to the phenomenon of buoyancy, which is also observed in other fluids, but is especially strong in liquids due to their high density. Liquid components in a mixture can often be separated from one another via fractional distillation.
The volume of a quantity of liquid is fixed by its temperature and pressure. Unless this volume exactly matches the volume of the container, a surface is observed. Liquids in a gravitational field, like all fluids, exert pressure on the sides of a container as well as on anything within the liquid itself. This pressure is transmitted in all directions and increases with depth. In the study of fluid dynamics, liquids are often treated as incompressible, especially when studying incompressible flow.
If a liquid is at rest in a uniform gravitational field, the pressure 
at any point is given by
where:
= the density of the liquid (assumed constant)
= gravity
= the depth of the point below the surface.
Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected.
Liquids generally expand when heated, and contract when cooled. Water between 0 °C and 4 °C is a notable exception; this is why ice floats. Liquids have little compressibility: water, for example, does not change its density appreciably unless subject to pressure of the order of hundreds bar.
Examples of everyday liquids besides water are mineral oil and gasoline. There are also mixtures such as milk, blood, and a wide variety of aqueous solutions such as household bleach. Only six elements are liquid at room temperature and pressure: bromine, mercury, francium, cesium, gallium and rubidium. In terms of planetary habitability, liquid water is required for the existence of life.
Separating Solids
Solids can be separating from other solids by sieving. In general, a sieve separates wanted/desired elements from unwanted material using a tool such as a mesh, net or other filtration or distillation methods. The word "sift" derives from this term. A strainer is a type of sieve typically associated with separating liquids from solids.
What Is A Solid?
Quantities of liquids are commonly measured in units of volume. These include the litre, not an SI unit, and the cubic metre (m³) which is an SI unit.
Some Links To Find More Info And Cool Things To Try!
Click on the link buttons below to learn lots more about solids, liquids and gases.
Have fun!!!
Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
