Particulate Nature of Matter

The entire universe is made of two things: matter and energy. For the time being we will concern ourselves with matter only.

Matter

Matter is defined as that which has mass and occupies space. This definition seems simple enough, yet there are profound issues which surround it. For example, there is currently no generally accepted scientific theory for why mass exists. It can be defined: mass characterizes an object's resistance to a change in its motion. As we look into it more, definitions start to become circular, as in the definition of space: space is that which is occupied by matter. So, any definition of space exists only if there is matter.

All matter is particulate in nature. This basically means that between separate bits of matter there are spaces which contain no matter. In science it is called the "atomic nature of matter." Today, we know that there are many different particles which make up matter. The primary "particle" in chemistry is the atom. Matter is made up smallest particles known as atoms. Atoms are smallest particles which cannot be observed by the naked eye. These are smallest particles that take part in a chemical reaction. Atoms are made up of protons, electrons and neutrons.

Protons are positively charged particles, electrons are negatively charged particles and neutrons are neutral. Protons and neutrons are found in the nucleus of the atoms while the electrons are found on the shells. Matter is anything occupying space and having mass; it is the material of the universe.

States of Matter and their Interconversion

There are three main phases of matter: gases, liquids, and solids. There is also a fourth phase, plasma, but it exists at very high temperatures and molecules in that state can behave very differently.

Solids

Solids are materials in which the atoms or molecules are set in place. In ionic solids such as table salt crystals, the ions are connected to their neighbors by electrical attraction. The common point about solids is that the atoms or molecules are in place. The temperature that can be shown by solid materials is due to the movement in place of the atoms or molecules. They have no independent linear motion of translation because they are attached to one another. Solids can have molecular energy due to vibration and rotation. Solids show a definite shape and a definite volume. Unless forces are used that are not commonly found near the earth’s surface, solids can not be compressed.

Liquids

Liquids are an in-between phase of matter. They are right between solids and gases. One characteristic of a liquid is that it fills the shape of any container. So you pour some water in a cup. It fills up the bottom of the cup first and then fills the rest. It also takes the shape of the inside of the cup. One other characteristic of liquids is that they are very hard to compress. When you compress something you take a certain amount and force it in a smaller space. Solids are tough to compress too but ...

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Liquids

Liquids are an in-between phase of matter. They are right between solids and gases. One characteristic of a liquid is that it fills the shape of any container. So you pour some water in a cup. It fills up the bottom of the cup first and then fills the rest. It also takes the shape of the inside of the cup. One other characteristic of liquids is that they are very hard to compress. When you compress something you take a certain amount and force it in a smaller space. Solids are tough to compress too but gases are easy. When you compress something you squeeze it so the atoms in the substance are closer together. When pressure goes up, Substances are compressed. Liquids already have their atoms close together so it's hard to push them even closer. Atoms in a liquid have more energy than the atoms in a solid. In a liquid the forces that hold the particles of liquid close to each other are greater than the forces due to motion that would force the particles away from each other. The property of liquids of incompressibility is useful to us in hydraulic machines. Simple systems of automobile hydraulic brakes are a good example of this. The brake pedal pushes a master cylinder. The travel of the brake petal is a few inches. The master cylinder pushes a small area of a liquid (hydraulic fluid) down a small tube (the brake lines) to the wheel cylinders. The wheel cylinders have a much larger area, but they go a shorter distance to push the brake pad against the drum or rotor, depending on what kind of brakes you have. The brake system cannot work correctly if there is any air (gas) in the system because the gas is compressible.

Gas

Gas is everywhere. There is something called the atmosphere. That's a big layer of gas that surrounds the Earth. Gases are random groups of atoms. There are solids where atoms and molecules are really compact. Liquids have them a little more spread out. But gases are really spread out and the atoms and molecules are full of energy, bouncing around constantly. One of the physical characteristics is that a gas can fill a container of any size or shape. Think about a balloon for a minute. No matter what shape you make the balloon it will be completely filled with the gas. The atoms and molecules are spread equally throughout the entire balloon. Liquids can only fill the bottom of the container while gases can fill it entirely. It is the most energetic phase of matter commonly found here on earth. Interconversion of Matter

Interconversion of Matter

Matter can change from one state to another by the use of energy.

The six changes of state

Melting is the change from a solid to a liquid.
Vaporization is the change from a liquid to a gas. Slow vaporization is called evaporation. Fast vapourization is called boiling.
Condensation is the change from a gas to a liquid.
Solidification, or freezing, is the change from a liquid to a solid.
Sublimation is either the change from a solid directly to a gas, or the change from a gas to a solid. Notice that sublimation is the name for two possible changes of state

Kinetic Theory

The kinetic theory helps to explain the way in which matter behaves. The evidence is consistent with the idea that all matter is made up of tiny particles. This theory explains the physical properties of matter in terms of the movement of its constituent particles. The main points of the theory are:

All matter is made up of tiny, moving particles, invincible to the naked eye. Different substances have different types of particles (atoms, molecules or ions) which have different sizes.
The particles move all the time. The higher the temperature, the faster they move on average.
Heavier particles move more slowly than lighter ones at a given temperature.

The kinetic theory can be used as a scientific model to explain how the arrangement of particles relates to the properties of the three states of matter. The particles that make up matter (atoms) are always in constant motion. These particles are held together by the We think that all matter is made of particles. There are forces between these particles and these forces hold the particles together (in solids and liquids). However, the particles are also moving. The higher the temperature of a material, the more its internal energy and the more energy its particles have. In a solid, this means they vibrate more vigorously; in liquids and gases, it means they move faster.

Brownian Movement

Brownian movement is the random motion of visible particles caused by much smaller, invisible ones.

Brownian motion is the erratic and constant movement of tiny particles when they are suspended in a fluid or gas. For example, if you sprinkle tiny grains of dust into some water, and then look at the dust particles under a microscope, the dust particles will appear to dance around, quite randomly.
This zigzag motion happens regardless of how still the water is.

The phenomenon was discovered in 1827 by the British botanist Robert Brown. He was investigating pollen grains in water, and noticed that they wouldn't sit still under his microscope. At first he thought the pollen was moving because it was alive. But even hundred-year old pollen grains danced around. When he looked at non-living particles, they moved too, so he knew there had to be some other explanation.

Further experiments by Brown and others showed that the motion became more rapid and the particles moved farther in a given time interval when the temperature of the water was raised, when the viscosity of the fluid was lowered, or when the size of the particles was reduced. The molecules of the liquid will move faster when the liquid is heated, causing more agitated Brownian movement of the big particle. Similarly, if you make the liquid less viscous, the molecules can move more easily, also resulting in more particle motion. And of course, if the particle is too big, the random bumps by molecules won't be noticed at all.

Diffusion and How does Molecular Mass affect the Rate of Diffusion

Diffusion is defined as the spreading out from a concentrated source which results in an increase in the entropy (degree of disorder) of the substance. Diffusion occurs because of the random movement of molecules of the substance which allows them to separate from one another. The greater the space between these molecules the greater the ability for the molecular particles to spread out from one another. The more packed the molecules are in the substance the less space to maneuver, and therefore, the more difficult for diffusion to occur. For example, solid substances are composed of particles (molecular or ionic) that are more tightly packed together. Because of this tight packing, the particles are not capable of diffusing very rapidly so the speed of diffusion occurs very slowly. If you placed a Lead brick and a gold brick in contact with one another and wrapped them together, it would take several years before the two bricks were "glued" together. This adhesion of the two bricks to one another is due to the fact that the Lead and Gold atoms are moving very slowly. The atoms are able to diffuse into each others solid matrix thus causing them to adhere to one another but only after several years being in contact with each other's surface.

On the other hand, liquid substances are composed of particles that are less packed and indeed can move more freely. Having more space between the liquid particles makes diffusion more likely to occur at a faster rate. For example, if one placed a drop of liquid colored ink into a glass of liquid water the ink drop would slowly but noticeably diffuse out throughout the water. Since the ink particles are farther away from each other, and the water molecules are spread out, the molecules of ink can diffuse fairly rapidly so that the water is colored homogeneously throughout with the color of the ink in a matter of minutes. Gaseous substances are in a league all to themselves. The molecular particles of gas are much more distant from one another than either liquid or solid particles are to each other. That is why gases are transparent. Light can pass through the relatively large spaces between the molecules of gas without any distortion. Liquids distort light more so because the particles are closer, and the light passing through a liquid can be deflected more easily. If a gas possessing an odor such as Ammonia were allowed to escape an open bottle, it would not take but a few seconds for the detectable odor of Ammonia to be detected throughout the room. Ammonia gas molecules having a great deal of space between the particles of Ammonia and air could travel at a faster rate.