The Particle Nature Of Matter.docx

THE PARTICLE NATURE OF MATTER These characteristics that describe a sample of matter are called properties You measured the mass of each sample of matter using a balance or a weighing scale. The mass of an object is a measure of the amount of matter the object has. The measure of the space occupied by an object is called volume. There are other properties of matter such as hardness, texture, color, flexibility, malleability, and electrical conductivity which vary from one sample to another. Almost 2,500 years ago, Leucippus and his disciple, Democritus believed that nature consisted of two things, “atoms and the void that surrounds them” (Knieram, 1995-2013) Democritus, atoms are indestructible and completely full, so there is no empty space. atomos, a Greek word which means indivisible particle. John Dalton presented concrete evidence that all matter is made of very small particles called atoms. An atom is the smallest particle of an element that has all the properties of the element. A molecule is a particle consisting of two or more atoms combined together in a specific arrangement. The size of an atom is measured in angstroms. One angstrom is a unit of length equal to one ten millionth of a millimetre. The scanning tunneling microscope (STM) allows scientists to view and scan the surface of very small particles like atoms. Pointillism is a method of painting using dots to come up with various effects. The dots are placed singly, in rows, or randomly. models, which are drawings or diagrams that are representations of what is happening at a level beyond what your eyes can see. This is what science educators call the sub-microscopic model of representing an idea or concept, which you cannot observe with your senses or even aided by a simple microscope. Matter shows that in gases, the particles move at random directions very quickly and travel in straightline paths. Gases take the shape of the container because the particles are able to move freely to all parts of the container. In liquids, the particles are closer to one another, nudging one another as they move. Solids have definite shapes and volume because the particles are packed closely together in fixed positions. The process by which the molecules on the surface of a liquid break away and change into gas is called evaporation. This process where a gas is changed into a liquid is called condensation. It is the reverse of evaporation. More molecules therefore have the energy to overcome the forces of attraction of the adjacent molecules. These molecules escape to the gaseous phase. This is evaporation. The molecules that escape from the liquid and go into the gaseous phase is called vapor When a gas is cooled, the motion of the particles slows down. If the particles lose enough energy, their attraction for each other can overcome their motion and cause them to associate with one another to become a liquid. This process is called condensation. This transformation process in which a solid is changed to a liquid is called melting. Freezing is the process in which a liquid is changed to a solid.

ATOMS: INSIDE OUT J.J. Thomson was able to discover that atoms have negatively-charged particles, which he called electrons. It led him to propose a new model for the atom, which he called the plum pudding model. Since plums and puddings are not commonly known in the Philippines, it may work better for you that we use the other name for the model, the raisin bread model. A group of scientists composed of Ernest Rutherford, Johannes "Hans" Wilhelm Geiger and Ernest Marsden tested Thomson’s model by bombarding a very thin sheet of gold foil with positively-charged alpha particles. Their experiment is referred to as the alpha particle scattering experiment. Similarly, the way the alpha particles “bumped”, or did not “bump”, the particles in the atoms of the gold foil led Rutherford’s team to propose another model for the atom, the nuclear model. All atoms of an element contain the same number of protons in their nuclei. This number is the element’s atomic number. Atoms having the same number of protons but different number of neutrons are referred as isotopes. The isotopes are identified through their mass number which is the sum of the number of protons and the number of neutrons in an atom. A shorthand notation for isotope includes the element’s symbol and mass number PERIODIC TABLE OF ELEMENTS in 1817 to the work of Johann Dobereiner, a German chemist who formed the triads of elements with similar properties like the triad of calcium, barium and strontium. In 1863, John Newlands, an English chemist proposed the Law of Octaves. He based his classification of elements on the fact that similar properties could be noted for every eight element when they are arranged in order of increasing atomic masses. Lothar Meyer and Dmitri Mendeleev both came up with periodic tables that showed how elements should be grouped. in 1914, Henry Moseley, an English physicist observed that the order of the X-ray frequencies emitted by elements follows the ordering of the elements by atomic number. periodic law which states that the properties of elements vary periodically with atomic number. The vertical columns of the periodic table, called groups, identify the principal families of elements.