Matter can be classified into two categories: pure substances and mixtures. This classification is based on the internal composition of that matter. Using composition to describe matter is better than using its state, because the internal makeup makes matter unique, and not its phase or state. Example, water ( ) can be vapor, solid or the usual liquid. This means that scientifically, it is not correct to say water is a liquid, even though we all know that water is usually a liquid.
In a similar vein, classifying matter only according to its color, size, or weight is not enough because two identical objects can be of the same color, but their internal makeup may be different. Example, a glass of water from a lake may look and weigh the same as another identical glass of water from another lake — but it does not mean they are the same. They are all water, but the chemical compositions may be very different.
First, it is very important to be very clear what some
words mean. Let us begin with Elements
Elements
An
element is a substance made from only one type of atom. For example, Oxygen (
) is
an element made up of ONLY oxygen atoms. To understand this better, let us see
the how atoms behave.
Every element is made up
of atoms. Atoms are the smallest piece that can exist in an element. You will
need to put millions of atoms together to get an element of about half
millimeter in size. An atom is made up of ‘Electrons, Protons and Neutrons’. The diagram on your left is an illustration of an atom. The center part is the nucleus.
Atoms in some elements do not join up with other atoms of the same element. An example is Helium. Helium atoms exist alone and can look like this:
Some
atoms can also join up with other atoms of
the same element. When two or more atoms join up, they form a molecule. Oxygen, (
) is a
molecule because it has two atoms joined together. An oxygen molecule looks
like those in the diagram above.
Elements are pure in nature. They may vary in size as long as the atoms joining to make its molecules are the same. As soon as a different atom joins (bonds), it ceases to be an element — it is now a compound.
Elements are pure in nature. They may vary in size as long as the atoms joining to make its molecules are the same. As soon as a different atom joins (bonds), it ceases to be an element — it is now a compound.
Sometimes, atoms can join up
with other atoms of other elements in chemical bonds. When that happens, a
compound is formed. This means that a molecule can be made up of two atoms of
the same element, OR can be made up more atoms of different elements.
Compounds
A compound is a substance made from two or more elements that
have reacted chemically with each other. The elements in the compound can NOT
be separated by physical means.
Let us see this example below:
Let us see this example below:
Water is a compound. It is written as . This means it is a chemical bond of two elements—Hydrogen and Oxygen. It is written as because there are two atoms of Hydrogen, making it a hydrogen molecule, bonding with one atom of Oxygen.
Note that there are so many ways that molecules of elements join together, forming millions of compounds. All compounds are molecules but not all molecules are compounds.
It is also important to note that compounds do not necessarily look like the elements that formed it. Compounds are usually a result of a chemical reaction or bond, which means that they are entirely new materials. For example, Hydrogen and Oxygen elements are both gases, but after bonding chemically, they form water, which is liquid at room temperature.
Another good example is Iron sulfide, a compound formed from bonding two elements— iron and sulfur.
Substances
A substance is simply matter with definite chemical composition and distinct properties. It is matter that is characterized by a constant composition in terms of its molecules, formulae and atoms, as well as physical properties such as density, refractive index, electric conductivity, melting point, and so on.
A substance can be an element or a compound but NOT a mixture. It can also be matter that exists in its pure form, usually called a pure substance. A few examples of substances include Water ( ), Hydrogen ( ) and Neon (Ne).
Other examples of chemical substances commonly seen in pure form are salt (sodium chloride), diamond (carbon) and gold.
The diagram
above shows the classification of matter and where substances fit.
Substances cannot be separated into components by physical separation techniques. Some substances, like water, can be broken down into elements by a chemical reaction (to break chemical bonds). A substance can be solid, liquid, gas, or plasma.
Substances cannot be separated into components by physical separation techniques. Some substances, like water, can be broken down into elements by a chemical reaction (to break chemical bonds). A substance can be solid, liquid, gas, or plasma.
Mixture
A mixture is
formed of little bits of one or more substances mixed together. Usually, the
parts can be separated from each other by physical means, because it
does not involve any chemical reactions or bonds.
Types of Mixtures
A mixture can involve two or more substances of the same phase or different phases. For example you can mix water and sand (liquid and solid), sugar and salt (solid and solid), water and oil (liquid and liquid) or nitrogen and oxygen (gas and gas). Clearly, mixtures can vary a lot and can be homogeneous or heterogeneous.
Types of Mixtures
A mixture can involve two or more substances of the same phase or different phases. For example you can mix water and sand (liquid and solid), sugar and salt (solid and solid), water and oil (liquid and liquid) or nitrogen and oxygen (gas and gas). Clearly, mixtures can vary a lot and can be homogeneous or heterogeneous.
Homogeneous mixture:
Mixtures involve mixing substances, so let us first be clear what a homogenous substance is. When a sample of matter has the same composition throughout, we call that substance a homogeneous substance. A cup of water will have the same chemical composition throughout . That makes it a homogeneous substance. A piece of gold will also have the same chemical composition, making it a homogenous substance. Homogeneous Mixtures behave in a similar way — the substance formed appear to have the same chemical composition. Alloys and Solutions are Homogeneous mixtures.
Mixtures involve mixing substances, so let us first be clear what a homogenous substance is. When a sample of matter has the same composition throughout, we call that substance a homogeneous substance. A cup of water will have the same chemical composition throughout . That makes it a homogeneous substance. A piece of gold will also have the same chemical composition, making it a homogenous substance. Homogeneous Mixtures behave in a similar way — the substance formed appear to have the same chemical composition. Alloys and Solutions are Homogeneous mixtures.
A mixture can also result in two or more phases clearly separated by boundaries. Very often, the separation can be clearly seen by the eye. A heterogeneous mixture is one that does not have uniform properties and composition. Take a look at a bowl of cereal with nuts. A spoon full will surely have a different number of nuts than a second spoonful taken at random. Another example—take some sea-sand into your palms. Look at it closely and you will notice that some sand particles are bigger than others, and the colors of some particles may be different too. They are NOT uniform in any way.
Heterogeneous mixtures include colloids, emulsions or suspensions.
Hello iin... Can you explain what holds an electron revolving around the nucleus? Why don't they just go zooming around everywhere?
BalasHapusWhat causes the force that holds atoms together? The answer is electricity and magnetism. The atom's center, or nucleus, is positively charged and the electrons that whirl around this nucleus are negatively charged, so they attract each other. The reason the force is strong is because the atom is so small. The distance between the nucleus and the electrons is about 1 Angstrom (named after a famous scientist); this is 0.00000001 cm (10-8 cm) or about 4 billionths of an inch. Since the electric force varies with the distance between the positive and negative charges like 1 over the distance squared, the force gets large for small distances.
HapusLeh uga
BalasHapusI would like to ask to you, why atoms have orbital?
BalasHapusPlease explain and thank you
oke santa... why atoms have orbital?? Atoms form bonds because the resulting compound is more stable than a single atom. When they are attached, each atomic orbitals combine to form new orbitals, ie molecular orbitals. Bonds formed an element can be either ionic or covalent bonds, depending on how big the price difference in electronegativity of elements that bind them. When kelektronegatifannya small differences, such as would occur in organic compounds, then these elements form a covalent bond.
HapusI would like to ask to you, why atoms have orbital?
BalasHapusPlease explain and thank you
Is vacuum matter?what are ten things that are not matter?? @rico gorat
BalasHapusA vacuum, to us, is a space with no matter in it. As a practical matter though, it's really a space with very little matter in it. You might already know that it's REALLY hard to get all the matter out of any space. Believe it or not, vacuums are very important and are becoming more useful every day. There is actually a whole branch of science dedicated to creating and studying vacuums.
HapusMany modern devices (like the integrated circuit chips that make everything from cars to computers work), have to be fabricated in a vacuum. Jefferson Lab uses vacuums for thermal insulation. A lot of our equipment will only work at extremely cold temperatures. We operate at 2 degrees above the lowest possible temperature in the universe - you bet we're paying attention to insulation! If you could insulate your home with the same insulating vacuum that we use for our accelerator then you wouldn't need a furnace at all!
Even outer space, which is considered a vacuum and has less matter in it than anything mankind can reproduce, still has some atoms bouncing around.
what atoms make up sugar? After sugar is melted over heat, what is the black substance called?
BalasHapusoke gabriella... Sugar is a type of carbohydrate. It turns out there is a whole class of carbohydrates called "sugars." The kind of sugar we usually think about - table sugar - is called sucrose. Sugar is made up of carbon, hydrogen and oxygen atoms. It's the way these atoms are connected that makes each type of carbohydrate different. In each molecule of table sugar there are: 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms.
HapusThe black stuff is called burnt sugar! But seriously, this is what happens when you heat or burn things that contain carbon. It reacts with oxygen and "oxidizes" (burns). The black stuff itself is mainly carbon. So is the soot inside a chimney.
Unfortunately, the bacteria in your mouth also love to eat sucrose (more than you do). When they do, they produce that yucky stuff called plaque that rots your teeth and gums.
Anything with an atomic number greater than 95(uranium) is called transuranic. These elements are man made, but is there a difference in any way besides that? How are these elements created?
BalasHapusPlease explain it.!
We generally call the transuranics "man-made" elements because they are normally not found in nature. However, it has been verified that some of these elements are produced and found in nature in very small amounts. It's likely that all of them (and maybe more) exist somewhere in the universe, but the only way to get them in any useful amounts is to make them yourself.
HapusYou asked a couple questions, let's look at them separately.
First, there is nothing inherently different about transuranic elements. They do share some common characteristics. As a class, they are all radioactive. But that's also true of all elements above atomic number 82 (lead) (Pb-208 being the heaviest stable isotope known). And radioactivity is actually far more common than stability if you look at all the known nuclides. The transuranics also share the trait that they will undergo nuclear fission. We'll look at that later, also check the link for more info. But these traits are not unique to the transuranics. Uranium is also fissionable, and elements as light as atomic number 88 (radium) may undergo fission (but not very efficiently). We also should keep in mind that there are many isotopes that are much lighter than uranium which are only available by "artificial" means. So, again, there's no unique property that applies only to "man-made" isotopes or transuranic elements.
HapusSecondly, you asked how these elements are created. The short answer is that they are produced in particle accelerators and nuclear reactors. For the long answer, let's examine the actual process of how they are made. Let's think for a moment how we would create any element - whether it be transuranic or otherwise.
Atoms are collections of neutrons and protons (with some electrons attached to complete the picture). As you probably know, changing the number of protons changes the element. So an atom with one proton (regardless of how many neutrons it has) is hydrogen, an atom with two protons is helium, etc. So if I want to create atoms with, say 10 protons, I have to figure out a way to get ten protons together along with enough neutrons to keep those protons together. It seems logical that the easiest way to do that might be to start with atoms having nine (or maybe eleven) protons, and see if I can add (or subtract) one from there. So, I need to cause a nuclear reaction, or change. Nuclear changes take lots of energy, because there is tremendous force (called, the strong force) holding nuclear particles together. This is different than chemical reactions - which only involve electrons. Electrons aren't held in atoms with nearly as much force as nucleons, so there's not as much energy needed to rearrange them. So, we have to impart energy to the nucleus. This is done by hitting it with something. Now, nuclei are very selective about what they will allow themselves to be hit by. They have a kind of "energy shield" around them. To get past this shield, other particles generally need lots of energy. So, one way to hit the nucleus is to raise the energy of some particles high enough to do that, and fling them at the nucleus - a particle accelerator. The idea is basically to shoot particles at a particular target material having properties that will result in the desired product material. Some particles work better for this than others. Very high energy photons (extremely energetic x-rays) will also do this - but you need an accelerator to produce these photons. So, particle accelerators like Jefferson Lab can and do change the nuclear structure of the materials exposed to the particle beam. This is how many of the radio-isotopes for pharmaceutical use are made. In the case of some of these rare isotopes, there is only one facility (a National Laboratory accelerator) at which the material is produced.
Now, where do we find enough free neutrons to perform all those tricks we just did? Usually, in a nuclear reactor. Earlier, we said uranium and other heavy atoms were fissionable. This means they have the property that when they absorb a neutron, sometimes the result will be that the new nucleus breaks in two - or fissions. This fission event is very energetic (remember, there is a lot of force holding this nucleus together). So, the fragments go flying apart from each other with great force. If you can get lots of these atoms to fission, you can release a lot of energy (as heat). Now, the stroke of luck that allows this to happen is that each time a fission event occurs, several neutrons are also released from the atom. So, one fission event can provide the free neutrons needed to cause two or three more fission events. If we design our reactor correctly (the right materials, size, shape, amount of fuel, etc.) we can have plenty of neutrons available to make the fission process self-sustaining - and have plenty of them left over to be absorbed by other atoms - to produce transuranics, for example. The isotope U-235 makes a very good fuel for fission. But remember, most uranium is U-238. So, if we fuel a reactor with a combination of U-235 and U-238, we have both the fission fuel and the target for making transuranics. And once we let the fission process begin, we have the neutrons necessary to make both things happen.
can you give me another example of compound, please!
BalasHapusExamples of Compounds:
Hapus1. Water - Formula: H2O = Hydrogen2 + Oxygen
Two atoms of the element Hydrogen combine with one atom of Oxygen through a covalent bond to form water. Hydrogen has a slightly positive charge and oxygen has a negative charge, and therefore it forms a polar molecule. Water can be split back into hydrogen and oxygen through electrolysis.
2. Hydrogen Peroxide - Formula: H2O2 = Hydrogen2 + Oxygen2
Hydrogen peroxide is formed when two atoms of hydrogen form a bond with two atoms of oxygen that have bonded to each other. Although it has only one more oxygen atom than is present in a molecule of water (H2O), its properties are very different.
3. Salt - Formula: NaCl = Sodium + Chlorine
In salt, one atom of sodium bonds to one atom of chlorine to produce the resulting ionic compound sodium chloride. Salt is quite easily produced for commercial uses by simply evaporating seawater, although it can be mined from the ground as well. Sodium chloride can be separated into its different atoms through electrolysis.
4. Baking Soda - Formula: NaHCO3 = Sodium + Hydrogen + Carbon + Oxygen3
Sodium bicarbonate (baking soda) can be produced from the reaction of carbon dioxide with an aqueous solution of sodium hydroxide, which creates sodium carbonate; it is then combined with carbon dioxide molecules to produce sodium bicarbonate. It is found naturally in hot springs and other places on earth, but is commercially produced for industrial uses.
5. Octane - Formula: C8H18 = Carbon8 + Hydrogen18
Octane is a hydrocarbon whose actual formula is CH3(CH2)6CH3. It's a low-molecular weight compound, which means its highly volatile and flammable, making it ideally suited for the production of gasoline.
hi iin stg..
BalasHapusDoes that cause a substance can be dissolved in a homogeneous mixture? may try to exemplify and explain?
Thank You...
A solution is a specific type of mixture where one substance is dissolved into another. A solution is the same, or uniform, throughout which makes it a homogeneous mixture . Go here to learn more about mixtures. A solution has certain characteristics: It is uniform, or homogeneous, throughout the mixture It is stable and doesn't change over time or settle The solute particles are so small they cannot be separated by filtering The solute and solvent molecules cannot be distinguished by the naked eye It does not scatter a beam of light Example of a Solution One example of a solution is salt water which is a mixture of water and salt. You cannot see the salt and the salt and water will stay a solution if left alone. Parts of a Solution Solute - The solute is the substance that is being dissolved by another substance. In the example above, the salt is the solute. Solvent - The solvent is the substance that dissolves the other substance. In the example above, the water is the solvent.
HapusDissolving A solution is made when one substance called the solute "dissolves" into another substance called the solvent. Dissolving is when the solute breaks up from a larger crystal of molecules into much smaller groups or individual molecules. This break up is caused by coming into contact with the solvent. In the case of salt water, the water molecules break off salt molecules from the larger crystal lattice. They do this by pulling away the ions and then surrounding the salt molecules. Each salt molecule still exists. It is just now surrounded by water molecules instead of fixed to a crystal of salt. Solubility Solubility is a measure of how much solute can be dissolved into a liter of solvent. Think of the example of water and salt. If you keep pouring salt into water, at some point the water isn't going to be able to dissolve the salt. Saturated When a solution reaches the point where it cannot dissolve any more solute it is considered "saturated." If a saturated solution loses some solvent, then solid crystals of the solute will start to form. This is what happens when water evaporates and salt crystals begin to form. Concentration The concentration of a solution is the proportion of the solute to solvent. If there is a lot of solute in a solution, then it is "concentrated". If there is a low amount of solute, then the solution is said to be "diluted." Miscible and immiscible When two liquids can be mixed to form a solution they are called "miscible." If two liquids cannot be mixed to form a solution they are called "immiscible." An example of miscible liquids is alcohol and water. An example of immiscible liquids is oil and water. Have you ever heard the saying "oil and water don't mix"? This is because they are immiscible. Interesting Facts about Solutions There is a solvent called aqua regia which can dissolve the noble metals including gold and platinum. You can't see a beam of light when shining it through a true solution. This means fog is not a solution. It is a colloid. Solutions can be liquid, solid, or gas. An example of a solid solution is steel. Solids are generally more soluble at higher temperatures. Carbonated beverages are made by dissolving carbon dioxide gas into liquid at high pressure.
Hapuswill scientists ever find smaller elements or is hydrogen the smallest possible?
BalasHapushello eldaniel...
HapusThe number of protons in an atom's nucleus determines which element it is. To make an element simpler than hydrogen, one would have to remove a proton from hydrogen's nucleus. This is a problem since an atom of hydrogen only contains one proton to begin with. Remove that proton and you no longer have an atom. Hydrogen, which contains a single proton in its nucleus, is the simplest element.
When it started the development of scientific concept of atoms??
BalasHapusIn chemistry and physics, atomic theory is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms. It began as a philosophical concept in ancient Greece and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of atoms.
HapusThe word atom comes from the Ancient Greek adjective atomos, meaning "indivisible".[1] 19th century chemists began using the term in connection with the growing number of irreducible chemical elements. While seemingly apropos, around the turn of the 20th century, through various experiments with electromagnetism and radioactivity, physicists discovered that the so-called "uncuttable atom" was actually a conglomerate of various subatomic particles (chiefly, electrons, protons and neutrons) which can exist separately from each other. In fact, in certain extreme environments, such as neutron stars, extreme temperature and pressure prevents atoms from existing at all. Since atoms were found to be divisible, physicists later invented the term "elementary particles" to describe the "uncuttable", though not indestructible, parts of an atom. The field of science which studies subatomic particles is particle physics, and it is in this field that physicists hope to discover the true fundamental nature of matter.
If I am mixing NaOH with Nacl what is the reaction going on?
BalasHapusAll acids if it reacts with a base will form salt and water. The reaction of acids and bases is known as the neutralizing reaction. It is said that the neutralizing reaction due to the acid and base reaction produces a neutral salt and water.
HapusExample:
HCl + NaOH → NaCl + H2O