Solids, liquids, and gases
Place an ice cube on the palm of your hand and you will soon have a pool of water. Leave it for long enough and the water will evaporate and disappear. What makes water appear as ice rather than a vapour? What makes it change between solid, liquid, and gas?
Every substance is made up of atoms or molecules that jiggle about in constant motion. Depending on how hot or cool it is, and how much "squeezing" (pressure) a substance receives from its surroundings, it's atoms or molecules move quicker or slower, spring together or bounce apart . It's the strange dance of atoms inside a substance that makes it shift between solid, liquid, gas,or plasma — the four main States of matter.
Although the solids,liquid, or gas forms of a substance contain the same number of atoms, they have different inner structures. Ice water, and water vapour look very different and behave in amazingly different ways - all because of the patterns their atoms take up inside them.
Solids
When something is cooled or put under pressure, it's atoms or molecules lock tightly together to form the strong bonds of a solid. These powerful links between atoms make solids difficult to bend or reshape. Some materials form orderly solids called crystals, while others form more random (amorphous) solids.
Water in a solid state
Most substances contract (shrink) when they freeze, but water is different. It expands as it freezes, making ice slightly less dense than water. This is why ice floats and why water pipes can burst when the fridge.
Crystalline solid
If you cool a liquid slowly it has time to arrange its atoms and molecules into a very regular form called a crystal. Many metals are like this.
Amorphous solid
Some materials cool and snap together into a more random structure. Glass is like this - a mix between an orderly solid and chaotic liquid.
Liquids
Liquids are usually hotter and less compressed than solids show their atoms and molecules are slightly further apart from one another. The forces between the particles are weaker, so they can move around freely. This is why liquids have no fixed shape, but spread out to line the container in which they are placed.
Water in a liquid state
Life exists on earth because there is water. It's liquid at everyday temperature and pressure,which means it's easy to transport and recycle, and just as easy for plants and animals to absorb.
Viscosity
The weaker bonds between atoms and molecules in liquids to flow as you pour them. A liquid's "viscosity" means how slowly or quickly it flows.
Gases
In gases atoms and molecules are not bonded together but move quickly and freely and have enough energy to flow all by themselves. Constantly bumping into one another, they spread how to fill whatever container they are inside.
Water in a gaseous state
Gases are normally hotter than their liquid forms which is why steam is hotter than water. Gases can also form when the pressure is low. In clouds, what is a cold gas (water vapour), due to the low air pressure high above Earth.
Plasma
Heat a gas or lower its pressure enough and atoms come apart to form a cloud with an electric charge, called a plasma.Plasmas are made of charged particles, called electrons, and ions and (atoms missing electrons), so they behave in strange ways when electricity and magnetism are nearby
Aurora
The northern lights (Aurora Borealis) happen when plasma from the Sun hits Earth's atmosphere and bends in its magnetic field.
Changing States of matter
Boil a kettle and you will transform water from a liquid to a gas (steam). Freeze food and you will change the water inside it into a solid (ice). It's easy to make water change States because it's solid, liquid, and gas forms can exist at everyday temperatures and pressures. It's harder to change materials like metals into liquids or gases as much higher temperatures and pressures are needed.
Sublimation
You can change a solid into a gas without making liquid first. The "dry ice" used to make smoke in theatres theatres is made from frozen lumps of carbon dioxide. Once exposed to the air, it heats up rapidly and forms a cold gas.
Deposition
Gases can turn directly into solids without first becoming liquids. If water vapour in the air is cooled enough, it condenses and freezes to form snow in clouds, or frost on the ground.
Freezing
As liquids lose energy, their atoms and molecules move about more slowly and gradually come together. Bonds form between them and they lock in a rigid structure, making a solid.
Melting
Solids change to liquids by melting. For instance, an ice cream quickly soaks up heat from the atmosphere. Water molecules in the ice gain energy and move apart, becoming liquid.
Condensation
If you pull a gas or lower its pressure, it will turn into a liquid. Water vapour inside your home will often condense on your Windows on cold days if the outside temperature falls low enough.
Evaporation
When you heat a liquid the atoms and molecules give much more energy. They collide more often and start to push apart. Some have enough energy to escape from the liquid, forming a gas (vapour) directly about it.
Hi
ReplyDelete