But even so, the nucleus at the centre would still be far too small to see and so would the electrons as they dance around it. To explain why we must look at the electrons. Unfortunately, much of what we are taught at school is simplified — electrons do not orbit the centre of an atom like planets around the sun, like you may have been taught.
Instead, think of electrons like a swarm of bees or birds, where the individual motions are too fast to track, but you still see the shape of the overall swarm. In fact, electrons dance — there is no better word for it. These patterns can vary — some are slow and gentle, like a waltz whereas some are fast and energetic, like a Charleston.
Each electron keeps to the same pattern, but once in a while it may change to another, as long as no other electron is doing that pattern already. Atoms have many nearest neighbors in contact, yet no long-range order is present. A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a nearly constant volume independent of pressure.
The volume is definite if the temperature and pressure are constant. When a solid is heated above its melting point, it becomes liquid, given that the pressure is higher than the triple point of the substance. Intermolecular or interatomic or interionic forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container.
The volume is usually greater than that of the corresponding solid, the best known exception being water, H 2 O. The highest temperature at which a given liquid can exist is its critical temperature. The spaces between gas molecules are very big. Gas molecules have very weak or no bonds at all.
A gas is a compressible fluid. Not only will a gas conform to the shape of its container but it will also expand to fill the container. In a gas, the molecules have enough kinetic energy so that the effect of intermolecular forces is small or zero for an ideal gas , and the typical distance between neighboring molecules is much greater than the molecular size. A gas has no definite shape or volume, but occupies the entire container in which it is confined. A liquid may be converted to a gas by heating at constant pressure to the boiling point, or else by reducing the pressure at constant temperature.
At temperatures below its critical temperature, a gas is also called a vapor, and can be liquefied by compression alone without cooling. A vapour can exist in equilibrium with a liquid or solid , in which case the gas pressure equals the vapor pressure of the liquid or solid.
A supercritical fluid SCF is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density confers solvent properties in some cases, which leads to useful applications.
For example, supercritical carbon dioxide is used to extract caffeine in the manufacture of decaffeinated coffee. This gives it the ability to conduct electricity. Like a gas, plasma does not have definite shape or volume. Unlike gases, plasmas are electrically conductive, produce magnetic fields and electric currents, and respond strongly to electromagnetic forces. The plasma state is often misunderstood, but it is actually quite common on Earth, and the majority of people observe it on a regular basis without even realizing it.
Lightning, electric sparks, fluorescent lights, neon lights, plasma televisions, some types of flame and the stars are all examples of illuminated matter in the plasma state. A gas is usually converted to a plasma in one of two ways, either from a huge voltage difference between two points, or by exposing it to extremely high temperatures. Another state of matter is Bose-Einstein condensate, but this state only occurs with super-low temperatures. Science knowledge changes as we discover new evidence.
Technology helps us find this evidence. To learn more about plasmas and Bose-Einstein condensates, read these two articles that look at these science ideas and concepts. States of matter Matter in our world. Use the interactive Moisture sources in our homes to find out how moisture enters our homes and how we can minimise and remove it. Visit the Scholastic website for simple states of matter activities.
These include a video, song and quiz. Add to collection. Nature of science Science knowledge changes as we discover new evidence. Related content To learn more about plasmas and Bose-Einstein condensates, read these two articles that look at these science ideas and concepts.
Looking at water — solid, liquid or gas Water molecules in drama Solid to liquid to gas Use the interactive Moisture sources in our homes to find out how moisture enters our homes and how we can minimise and remove it. Useful link Visit the Scholastic website for simple states of matter activities. Go to full glossary Add 0 items to collection. Explain cohesion. Investigate the properties of a non-Newtonian fluid. Describe the general process of crystal formation.
Materials see individual activities for materials. There are three common states of matter: Solids — relatively rigid, definite volume and shape. In a solid, the atoms and molecules are attached to each other. Liquids — definite volume but able to change shape by flowing. Gases — no definite volume or shape. Each of these states is also known as a phase. Vocabulary cohesion : When two molecules of the same kind stick together.
Related Resources Air In these activities students explore the impressive force of air and learn how air pressure affects their daily lives.
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