Chemistry Friends/Matter< Chemistry Friends
To separate mechanically, matter is divided manually or with a magnet(p.38).
Some mixtures can be separated by letting it sit so one substance sinks to the bottom of the container. This method is normally very slow but can be sped up by spinning the container (p.39).
Air is blown into the compound, causing some parts of it to froth and float to the top. The top portion is then skimmed off (p.38).
If you have a heterogeneous mixture with solids mixed in it, you can pour it through a filter to separate the solids from the fluids (p.38).
You can mix something into your solution that is soluble with some of the elements in the solution but not all of them (p.39).
Fractional distillation is achieved by boiling a liquid compound at different temperatures. The components vaporize at separate temperatures and so they can be separated (p.39).
In a compound where a solid is dissolved in a liquid is cooled to form crystals of the solid element. This happens naturally with salt or sugar water (p.39).
The mixture is dissolved into a solvent. The solvent goes through a porous material such as filter paper, and the elements of the compound separate at different rates in porous material. This creates rings or lines of different elements (p.39).
Everything is made up of elements. We are mostly carbon, hydrogen, oxygen, nitrogen, calcium and phosphorus. Elements consist of: protons, electrons, and neutrons. Neutrons and protons stay in the nucleus while the electrons orbit around.
When two or more elements are combined with definite proportions they are known as compounds . Water (H2O) and salt (NaCl) are both compounds because they are made of more than one element.
In a homogeneous mixture, you can't see the separate components. The prefix "homo" is used, because it indicates sameness. Homogeneous mixtures are often called solutions, or when the particles are slightly bigger, colloids. The particles in a homogeneous mixture are invisible to the naked eye, except for certain colloids where the particles may be seen if in a direct shaft of light .Metals such as stainless steel and bronze are homogenous mixtures.
Heterogeneous mixtures are mixtures where the different components are visible to the naked eye, "hetero" indicating difference. Suspensions are heterogeneous mixture that, when allowed to sit, will separate into their different components. Mixed vegetables, beach sand and oil-vinegar mixtures are all examples of heterogeneous mixtures .
There are a few ways to write the names for molecules. Every element on the periodic table has a name and a symbol. For instance, you can write the element hydrogen in two ways. Either you can just write out the name hydrogen, or you can write its symbol,H. The symbol is one or two (and in some cases, three) letters. The first letter is capitalize and the next is small.
Naming Ionic CompoundsEdit
When elements stick together in an ionic compound, there is a special way to write the compound. Say the is a compound of zinc and oxygen. Its names would be 'Zinc oxide' when writing the name, we change the last syllable of the last element to -ide. When you write the chemical formula, you use the symbols instead of the whole word. Also, you need to specify how many zinc and oxygen atoms are in each compound. Zinc has a charge of 2+ while oxygen is 1-. In order to make a stable compound, you want the charges to add up to zero. So you'd need two oxygen atoms for every zinc. This is the chemical formula: ZnO2. When naming an ionic compound with its full names, you don't need to say the amount to each element but you do if you are writing the symbols.
Naming Molecular CompoundsEdit
Naming molecular compounds is very similar to naming the Ionic ones. However, when naming the compound you need to specify how many of each atom there are. For instance, water's chemical formula is H2O. We write its full name dihydrogen oxide. we put the prefix 'di' on the hydrogen to say that there are two hydrogen atoms on each oxygen. Here's a list of the prefixes 1-10 ( pg.113)
- mono (you don't really need to write this, but you can.)
The periodic law is a law about the arrangement of elements according to their mass discovered by John Alexander Newlands in 1864. It stated: "When elements are arranged in order of increasing atomic mass, chemical and physical properties form patters that repeat themselves at regular intervals". (p.63).
The periodic table is divided into eighteen different columns, known as "families" or "groups". Each family of elements have similar characteristics, such as the number of electrons in their outer orbital or the way they react with other elements. The first family, which includes Sodium and Francium, have only one valence electron and all react violently with water.
Alkali metals are the metals in the very first group on the periodic table, on the far left side, excluding hydrogen, which is merely in that row for organizational purposes. Every element in this family have an ion charge of 1+, and have only one valence electron. This means that they are highly unstable and react very quickly with other elements. Alkali metals are especially reactive with water. The higher their atomic number, the more violently they react because they are more unstable. Rubidium and Potassium are both alkali metals.
Alkaline Earth metals are the elements in the second family, near they left side of the table. They have an ion charge of 2+ and they are quite reactive.
All the metals from the third group to the staircase line are known as "transition metals". They have varying ion charges, with some of them having more than one, and they have varying levels of reactivity. This section of elements contain many of the metals that we use daily, such as iron, copper, and tin.
Halogens are the non-metals located on the second last family of the periodic table, near the far right side of the table. They are highly reactive elements because of their ion charge of 1-.
Noble gases are the gases in the family to the far right side of the periodic table. They are known as "noble" because they are the only elements with a full valence shell, and as such they will not react with other elements easily. They are elements that are stable in normal conditions. These elements light up in different colours when an electric charge is passed through them. Helium, Neon and Argon are all noble gases.
This is the line between the metals and the nonmetals. It is called the staircase line because it resembles the steps of a staircase,
These are found on the right side of the staircase line.
Early Greek TheoriesEdit
The early Greeks only had the technology available to identify a few elements. The first seven elements identified were gold, silver, iron, mercury, tin, copper and lead. At the time, the Greeks only knew of seven planets or celestial bodies, and so gave each of the elements a celestial body and a symbol to represent them. The Greeks knew very little about the chemical properties of the elements, they merely used them for making tools and art. As time went on, it became apparent that having symbols would not be sufficient for all the elements, and so it was eventually changed to letters. (p.55).
Dalton's Atomic TheoryEdit
Dalton's theory is often called the billiard ball theory. He believed that atoms were neutrally charged spheres, with no real distinction between protons and electrons.
Bohr was the first chemist who theorized that elements have a positively charged nuclues with negatively charged electrons orbiting around it, where the electrons were divided into orbital groups, with a specific number of electrons in each shell. He figured that there would be a certain number of electrons in each orbital, and the number of electrons in the last shell would determine the chemical properties.
Electrons are negatively charged. They orbit around the nucleus. Each orbital requires a certain amount of electrons. When there aren't enough electrons to fill the orbital, the atom is positive. When the opposite happens and the atom has to open up a whole new orbital just for one or two little electrons. This atom is negatively charged. When a positively charged atom such as a sodium finds a negatively charged atom like chlorine, the chlorine gives his extra electron to the sodium who needs an extra one. Then the two of them become an ionic compound, sodium chloride.
The nucleus is the center of an atom. It comprises of both the positively charged protons and neutrally charged neutrons. It is the nucleus of the atom that makes up most of the weight of the atom, because electrons do not weigh enough to be significant. Each proton or neutron weighs 1 AU (Atomic Unit). You can find out how many protons or neutrons there are in an element by looking at the molar mass and the atomic number. The atomic number will be the number of protons, and the atomic number subtracted from the molar mass will be the number of neutrons.
The atomic number is the number of the element on the periodic table. It signifies how many electrons are orbiting the nucleus of the element, so as the atomic number gets higher, so does the number of electrons. For example, Carbon's atomic number is 12. That means it has 12 electrons, and therefore 12 protons. Elements are grouped together based on their atomic numbers, because the number of electrons an element has can affect it's properties.
Neutrons are the sub-atomic particle that has a neutral charge. They are located in the nucleus of the atom and weigh 1 AU. The number of neutrons in an element determine if it is an isotope or not.
An Isotope is an element with the normal number of protons and electrons, but has extra or fewer neutrons. The element is still neutrally charged because the protons and the electrons are still balancing each other out. The extra or missing neutrons add or subtract weight to the element. Isotopes can be found in nature, but they are generally not as stable as the normal version of the element. (p.76).
The mass number is the molar mass of an atom. It comprises of the combined mass of both the protons and the neutrons of the element. On the periodic table, the molar mass will rarely be a round number. This is because it is the average mass of all common isotopes of the element. Hydrogen has very few common isotopes, so it's atomic number is 1.01.
Monoatomic Ions are elements that have either gained or lost electrons to fill their valence shell. This makes them have either a positive or negative charge. They are also known as ions .
Cations are elements that have lost electrons to fill their valence shell. They have a positive charge as an ion because they have more protons than they do electrons. All alkali metals are cations because they will lose electrons rather than gain them to fill their last shell.
Anions are the opposite of cations in that they have a negative charge because they have gained electrons to fill their valence shell. Most non-metals will be anions because they are near the right side of the periodic table and will gain electrons rather than lose them. A goofy trick to remember which is which is to visualize a happy cat. This will help you remember that cations are positively charged.
Here is a short quiz on the Matter section:
- Jenkins, F., van Kessel, H., Tompkins, D., Lantz, O., (1996). Nelson Chemistry, British Columbia, Nelson Canada.
- Chemistry and You! (n.d.) 
- Ophardt, C., Virtual Chembook,(2003), 
- Dayah, M. (1997) Dynamic Periodic Table, http://www.ptable.com