Chemistry

=Physical Properties of Matter= Physical proprieties of matter are properties that can be measured or observed without changing the chemical makeup of the matter. Examples include size, shape, color and texture. Remember all objects take up space and have mass. You use your sense of taste and smell to tell the difference between spinach and an orange.


 * Physical properties**- The measurement of mass and other characteristics that can be seen without changing how that object looks are its physical properties. When you look at oranges, you know that they are oranges because of their color, shape, and smell. Mass, color, shape, volume, and density are some physical properties. The answers to the question about the present are physical properties.

[|Density] is an important physical property. Density is the mass of a substance per unit volume. [|Volume] is the amount of space an object occupies.


 * Chemical properties-** These are properties that can only be observed by changing the identity of the substance. A piece of paper burns and turns to a black substance. After the flame goes out you can no longer burn the new substance. The chemical properties have been changed.

**Properties are constantly changing...** Matter is constantly changing. Ice in your soda melts, glass breaks, paper is ripped. When ice in your soda melts where does it go? What does it become?

If you remember, ice is water in the solid state. If you don't remember this or don't know it, you should go back and review [|states of water]. When you drop the ice cube into the liquid, it begins to melt because the temperature is higher than that of the ice cube. It's like putting a snowman on your front lawn in July. The ice cube becomes liquid water. This is an example of a **physical change**. The solid water turned to liquid water. It doesn't turn into soil or macaroni. It remains water. If it did change into soil or macaroni, your drink would taste terrible and you would have an example of a **chemical change**.

Chemical changes are changing substances into other substances. If it could happen, ice changing into macaroni would be an example of a chemical change. A real example of a chemical change is spoiling milk or burning toast. Milk needs to be in the refrigerator or else it will go bad. If you've ever seen or smelled spoiled milk, it is not a pretty sight. The milk gets a sour odor and becomes lumpy. Unlike physical changes, you cannot reverse chemical changes. You can melt ice to get water and freeze that water to get ice again. You cannot make milk unspoiled.

States of Matter
According to the ** kinetic theory of matter **, all matter is made up of moving particles called molecules. There are four states of matter: solid, liquid, gas, and plasma. The state that matter is in depends on how fast the molecules are moving and how much attraction the molecules hae for one another. In order for matter to change from one state to another, energy must be added or removed. Each substance has its own freezing point, melting point, and boiling point. In other words, different substances change states at different temperatures.

In a **solid**, the molecules are close together. They do not move around very freely, but they do vibrate. A solid has a definite shape and volume. Solids can be described as crystalline (particles arranged in a regular, definite pattern) or amorphous (particles arranged in no particular order).
 * Solid **

**Liquid**
The molecules in a liquid are farther apart than the molecules in a solid. The force of attraction between a liquid's molecules is strong enough to keep the volume constant but not strong enough to give the matter a definite shape. The molecules in a liquid also move faster than the molecules in a solid. **Liquids** have a definite volume but no definite shape.

**Gas**
Compared to the molecules in solids or liquids, the molecules in gases are very far apart. They are also moving very quickly. Because the forces between the molecules are weak, gases have no definite shape or volume. Gases expand to fill and take the shape of whatever container they are in. Gases can be compressed. When they are compressed, their pressure increases.

**Plasma**
When the temperature of a gas is extremely high, some of the gas becomes electrically charged. These charges create new physical properties. The formation of plasma can be simulated in a laboratory. It also occurs naturally inside stars. When clouds of plasma come in contact with the earth's atmosphere, they produce colored lights, or auroras, in the sky.

[]

To find out how plasma televisions work, check out this site.

5th State of Matter
Several other less common states of matter have also either been described or actually seen. Some of these states include liquid crystals, fermionic condensates, superfluids, supersolids and the aptly named strange matter.
 * Bose-Einstein Condensates** represent a fifth state of matter only seen for the first time in 1995. The state is named after Satyendra Nath Bose and Albert Einstein who predicted its existence in the 1920’s. B-E condensates are gaseous superfluids cooled to temperatures very near absolute zero. In this weird state, all the atoms of the condensate attain the same quantum-mechanical state and can flow past one another without friction. Even more strangely, B-E condensates can actually “trap” light, releasing it when the state breaks down.

Phase Changes
One way to separate two substances from one another in a physical mixture is to take advantage of differences in their boiling points. Distillation is the technique used for this kind of separation. However sometimes one of the substances to be separated will chemically decompose before it reaches its boiling point. One way to remedy this problem is to reduce the pressure within the distilling flask sufficiently to lower the boiling point of the substance below it decomposition point. This is called reduced pressure distillation and is a common technique used among Organic Chemists.

=Mixtures= **Mixtures** are physical combinations of two or more pure substances (elements or compounds). As a physical combination one should be able to separate these substances from the mixture by physical methods so that no chemical change can take place during the separation. Substances can be separated from the mixture by taking advantage of any differences the substances have in physical properties. For example, most pure substances have different boiling points (temperature at which a substance will boil). If we can heat a mixture so that the lowest boiling substance will boil off before any other substance begins to boil, we will effectively be able to separate that substance from the mixture. One such laboratory resolution method is known as distillation. Other separation techniques include chromatography, settling out, filtering, evaporation, and centrifuging.
 * **Properties of Elements, Compounds, and Mixtures** ||
 * **Elements** || **Compounds** || **Mixtures** ||
 * made up of only one kind of atom || made up of more than one kind of atom || made up of more than one kind of molecule ||
 * can not be broken down by chemical means || can not be broken down by physical means || can be broken down by physical means ||
 * has same properties as atoms making it up || has different properties from elements making it up || has same properties as substances making it up ||
 * has same properties throughout || has same properties throughout || has different properties throughout ||

Mixtures can be classified according to how well they are mixed together. There are two kinds of mixtures: **heterogeneous** and **homogeneous.**

Heterogeneous Mixtures
The matter in most mixtures is heterogeneous. The substances in a heterogeneous mixture are not chemically combined and the individual substances are still visible. Each substance keeps its own identity and most of its own properties. No new substances are formed because the chemical composition of the substances have not changed. A substance in a mixture can be present in any amount and can be separated by physical means. The substances that make up a mixture determine the mixture's properties.

Homogeneous Mixtures
In a homogeneous mixture, the parts look the same throughout because their components are uniformly mixed together. Homogeneous mixtures are uniform in their distribution. If we took a sampling anywhere in the mixture, and then analyzed it as to its composition for each component we would find that the distribution was the same throughout the mixture. All solutions are said to be homogeneous mixtures.

=Separation Techniques= Most materials in our world are mixtures. Very few materials are pure substances. The art of separating mixtures is important because it enables us to isolate pure substances. Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition. Heterogeneous mixtures are not. Salt water is a mixture of water and NaCl and is homogeneous if thoroughly mixed, with all the salt dissolved. Oil in water is a heterogeneous mixture. Both types of mixtures can be separated into their component parts by physical means. A salt water mixture can be separated by distilling or evaporating the water and collecting the salt residue. An oil and water mixture will separate into an oil layer and a water layer because the materials are not attracted to one another and gravity "pulls" the denser water beneath the less dense oil. Settling, magnetic attraction, distillation, decantation, solubility, evaporation, filtration, chromatography, and manual methods are all means of separating the components of a mixture. Choice of method depends on the type of mixture and the characteristics of its components.

A heterogeneous mixture of solid and liquid or solid and gas is usually fairly easy to separate because of the 2 different physical phases. The solid may settle out, allowing you to pour off the liquid. This is called **//decantation//**. Or, maybe the liquid can be evaporated, leaving the solid behind. Or the mixture can be poured through a filter, catching the solid on the filter and allowing the liquid or gas to pass through. We use filtration frequently--in our coffee makers, automobile fuel lines, automobile air cleaners to name only a few examples.

A mixture of two or more solids is usually separated by utilizing the different chemical or physical properties of the substances. For example, a heterogeneous mixture of red M&M's and yellow jellybeans can be separated using the different colors or the different shapes of the solids. The parts of the mixture are large enough to be separated manually. A mixture of black peppercorns and white table salt might be separated this way as well. But what could be done with a mixture of sand and sugar? True, you could get a magnifying glass and tweezers and try picking out the grains of sand, but is there an easier way? Is there some property that sugar has that sand does not (or vice versa)? Could this be used to separate sand and sugar? If you said that sugar dissolves in water and sand does not, you are on the right track.

Homogeneous mixtures of a solvent and one or more solutes (dissolved substances) are often separated by chromatography. Chromatography works to separate a mixture because the components of a mixture distribute themselves differently. Food colorings are one example, a homogeneous mixture of a solvent and a single dye or combination of selected dyes that produce the desired color.

**Solutions** A **solution** is a homogeneous mixture in which one substance is dissolved in another substance. In a solution, two or more substances are uniformly mixed. The solution formed is the same in all parts. In a sugar-water solution, molecules of sugar are evenly spread throughout the molecules of water. Solutions consist of two parts: the solute and the solvent. The **solute** is the substance being dissolved. The **solvent** is the substance in which a solute is dissolved. The the sugar-water solution, sugar is the solute and the water is the solvent. The substance present in the largest amount is usually called the solvent. The most common solutions are those in which the solvent is a liquid. The solute can be a solid, gas or liquid. A solution with water as the solvent is called an **aqueous solution**. Water is considered to be a **universal solvent**. Another common solvent is alcohol. A solution with alcohol as the solvent is called a **tincture**. However, other types of solutions can be formed.
 * **Types of Solutions** ||
 * **Solvent** || **Solute** || **Example** ||
 * liquid || liquid || antifreeze ||
 * ^  || solid || sugar water ||
 * ^  || gas || soft drink ||
 * gas || liquid || humidity ||
 * ^  || solid || mothballs ||
 * ^  || gas || air ||
 * solid || liquid || dental fillings ||
 * ^  || solid || steel ||
 * ^  || gas || gas stove lighter ||

The Solution Process
When sugar is added to water, a solution forms. The dissolving action takes place on the surface of the crystal. Water molecules surround the surface molecules of sugar. The sugar molecules are held together only by weak bonding forces. The sugar molecules are attracted more to the water molecules than to each other. surround by water molecules, surface sugar molecules are carried away from the crystal surface. the process of diffusion causes the sugar molecules to distribute evenly within the water molecules. As the outer layer of molecules dissolves, the next layer is exposed to the water molecules. This process continues until all the sugar molecules are separated from each other and mixed evenly throughout the solution. Check out this animation to see how salt dissolves in water.

Rate of Solution
1. When a solution is stirred, particles of the solute move away form the crystal surface at a higher rate. This exposes more particles to the solvent sooner. Thus the solute dissolves at a faster rate. 2. Solution action occurs only at the surface of the solid solute. So if the surface area of the solute is increased, the rate of solution is increased. More solute molecules are in contact with the solvent when the solid solute is ground into a find powder. 3. If heat is applied to a solution, the molecules move faster and farther apart. As a result, the dissolving action is speeded up. Water is the most common substance on the earth. Water plays an important role in dissolving a great variety of substances. Because thousands of substances are soluble in water, water is sometimes called the universal solvent. However, you should also remember, that there are certain substances that will not dissolve in water. These substances are described as insoluble.

Solubility Factors
The solubility of a solute is a measure of how much of that solute can be dissolved a given amount of solvent under certain conditions. Two main factors that affect the solubility of a solute are temperature and pressure. Generally, an increase in the temperature of a solution increases the solubility of a solid in a liquid. The solubility of most solids is increased by raising the temperature of the solution. Raising the temperature of a gas-in-liquid solution decreases the solubility of the gaseous solute. Thus, the solubility of a gas is decreases as the temperature of the solution increases. For solid and liquid solutes, increases and decreases in pressure have practically no effect on solubility. For gases dissolved in liquids, an increase in pressure increases solubility and a decrease in pressure decreases solubility.

Subatomic Particles
An **electron** is a particle that moves around the nucleus forming a cloud of negative charge.

A **proton** is a particle that gives the nucleus its positive charge.

A **neutron** is a particle with no charge. Neutrons are also in the nucleus of the atom. A proton and neutron are equal in mass. However, both have masses more than 1800 times that of an electron.

All atoms of an element have the same number of protons. For example, every hydrogen atom has one proton in its nucleus. Every carbon atom has six protons. The number of protons in the nucleus of an atom determines what the element is. The number of protons in an atom is called the **atomic number**.

Build your own atoms here!

Atomic Mass
The mass of an atom depends on the number of protons and neutrons in its nucleus. Compared to the nucleus of an atom, the electrons have very little mass. The mass of a single proton or neutron itself is extremely small. A proton has a mass of 0.000 000 000 000 000 000 000 001 673 grams. Scientists have agreed upon a standard atomic mass unit to measure the mass of atoms. Protons and neutrons have a mass of about 1 amu each. Electrons are much smaller and have a mass of 1/1800 amus.

The mass number of an atom is simply the sum of the number of protons and neutrons. If you know the mass number and the atomic number, you can find the number of neutrons. The number of neutrons is found by subtracting the atomic number from the mass number.

**Periodic Table**
With so many elements already found and the possibility of more being discovered, chemists needed a way to organize them. Many systems were tried in order to make some sort of pattern in their properties to match the table. The modern periodic table, based on atomic number and electron configuration, was created primarily by a Russian chemist, Dmitri Mendeleev, and a German physicist, Julius Lothar Meyer, both working independently. They both created similar periodic tables only a few months apart in 1869. Mendeleev created the first periodic table based on atomic weight. He observed that many elements had similar properties, and that they occur periodically, hence the name, periodic table. From this, he made the periodic law. His periodic law states that the chemical and physical properties of the elements vary in a periodic way with their atomic weights. The modern one states that the properties vary with atomic number, not weight. Elements in Mendeleev's table were arranged in rows called periods. The columns were called groups or families. Elements of each group had similar properties. By Mendeleev's theory, they should have been perfectly arranged by increasing atomic weight.

There were some inconsistencies in the arrangement of the elements according to his law, however it wasn't until the early 1900's (1914) that a Prof Henry Moseley, a British Physicist, was able to determine the atomic numbers of all the known elements using an experimental technique. Moseley then proceeded to rearrange the elements according to increasing atomic numbers. Moseley's arrangement seemed to clear up the contradictions and inconsistencies of Mendeleev's arrangement. Moseley's periodic law is now considered the current Periodic Law.

The Periodic Table of the Elements is constructed and arranged so that similar chemical properties were arranged in vertical columns called **groups**. Because chemical properties are based on electron configurations we can use the table to predict chemical properties for elements.

Group 1 is also called the **alkali metal** family. These are strong metals that are unusually soft, silver in color, and very reactive toward oxygen and water. These elements are so reactive toward oxygen and water vapor that they are stored under an inert liquid to protect them from oxygen and water vapor.

Group 2 is called the **alkaline earth metals**. These metals are not as soft as Group 1 metals. They also react more mildly with oxygen and only react with water at temperatures where the water is steam.

Groups 3-12 are referred to as the **transition metal** groups. These metals are not as predictable because of the shielding effect of the inner electrons.

Group 13 is referred to as the **boron** **family**.

Group 14 is referred to as the **carbon family**.

Group 15 is referred to as the **nitrogen family.**

Group 16 is referred to as the **oxygen family**.

Group 17 is referred to as the **halogen** **family**.

Group 18 is referred to as the **Noble gas** group previously known as the inert gas group.