6Nscio1 La Colleen ching
- Feb 10, 2010THREE TYPES OF REACTION ACCORDING TO ENERGY CHANGES
1. ENDOTHERMIC / ENDERGONIC REACTION is a change in which materials take up energy fro the surroundings.
CO2 + H2O + sunlight ¡ú C6H12O6 (glucose)
2. EXOTHERMIC / EXERGONIC REACTION is change in which energy is released to the surroundings.
Example: Magnesium burns in air to produce magnesium oxide.
3. A THERMIC REACTION ¨C There is no change in its energy content.
Example: Hot water in thermos.
LAWS THAT GOVERN MATTER AND ENERGY
1. LAW OF CONSERVATION OF MASS
Mass is neither created nor destroyed in any transformation of matter.
(The mass of the reactant is equal to the mass of the product)
Example: A + B ¡ú AB
Atoms of two different types of elements may combine to form products,
but the atoms of the elements and products remain the same.
2. LAW OF DEFINITE COMPOSITION / PROPORTION
A pure compound is always composed of the same elements combined in a definite proportion by weight.
Example: H2O (water) is always composed of 2 atoms of H and one atom of oxygen.
3. LAW OF MULTIPLE PROPORTION
When two element combine to form more then one compound, the different weights of one that combines with a fixed weight of the other are in ratio of small whole numbers.
C + O2 CO 1 : 1
CO2 1 : 2
(The ratio of C and O in CO is 1 : 1 in other conditions such as CO2, it is 1 : 2)
4. LAW OF CONSERVATION OF ENERGY
Energy is neither created not destroyed in any transformation of matter.
Example: Mg + O2 ¡ú MgO + light
P.E. ¡ú H.E. ¡ú L.E.
A. PROPERTIES OF MATTER
Given a list of properties of matter, place the extensive properties in Column A and intensive properties in Column B.
Oxidation, weight, volume, taste, solubility, shape, malleability, length, mass and melting point.
COLUMN A COLUMN B
4. 4.5. 5.
B. CHANGES IN MATTER
Identify the changes which the following undergo:
1. Souring of milk ______________________
2. Melting of candle ______________________
3. Digestion of food ______________________
4. Rusting of iron ______________________
5. Stretching of rubberband ____________________
6. Burning of candle ______________________
7. Pulverizing salt crystal______________________
8. Chopping of wood ______________________
9. Burning of coal ______________________
10. Boiling of water ______________________
Classify as to whether the following are homogeneous or heterogenous mixtures in Column B and specify what kind of mixtures are these in Column C.
COLUMN A COLUMN B COLUMN C
1. Fresh milk
2. Nail polish
3. Ocean water
5. Muddy water
6. Sour milk
12. Strained calamansi juice
D. FORMS OF ENERGY
Identify what form of energy is associated with the following. (You can have 2 or more answers in one number).
1. Atomic bomb ___________________________
2. Sunlight ___________________________
3. Lightning ___________________________
4. Thunder ___________________________
5. Generator ___________________________
6. Automobile ___________________________
7. Photoflash bulb ___________________________
8. Wall clock ___________________________
9. Photosynthesis ___________________________
10. Refrigerator ___________________________
E. CLASSIFICATION OF PURE SUBSTANCE (ELEMENTS AND COMPOUNDS)
Classify the following samples as to whether they are elements or compounds in column A and whether they are acids, bases or salts in Column B.
SAMPLE CLASSIFICATION KINDS(SPECIFICATION)
(Column A) (Column B)
1. HCI _________________________ ________________________
2. MgO _________________________ ________________________
3. Iron _________________________ ________________________
4. Mercury _________________________ ________________________
5. Water _________________________ ________________________
6. Sulfur _________________________ ________________________
7. Helium _________________________ ________________________
8. Carbon Dioxide _________________________ ________________________
9. Copper wire _________________________ ________________________
10. Rock salt _________________________ _________________________
ATOMS and SUB-ATOMIC PARTICLES
I. ATOMIC THEORIES
The idea that matter is made up of very small particles called atoms, was first conceived by Democritus, a Greek Philosopher. However, he did not distinguish ¡°atoms¡± of compounds from elementary substances, but believed that there were as many kinds of atoms as there were kinds of substances.
DALTON¡¯S ATOMIC THEORY
In 1804, the Atomic Theory was fully developed by John Dalton, an English school master and accepted by chemists and physicists. Dalton reached the following conclusions about the structure of matter:
a.) Substances are composed of tiny, indivisible particles called atoms.
b.) Atoms of any given substances are identical and have the same weight, size and form.
c.) The atom is the smallest part of an element which can enter into a chemical change.
d.) Atoms of elements are permanent and cannot be decomposed.
e.) Chemical reactions usually involve the building up of atoms into molecules or the breaking down of molecules into atoms.
II. MODERN ATOMIC THEORY
New discoveries and experimentations led to several change on Dalton¡¯s Theory.
REVISIONS IN THE ASSUMPTIONS OF DALTON¡¯S THEORY
1. Atoms are complex and not simplest particles.
2. Not all atoms of the same elements are alike because some elements called Isotopes do not have the same mass.
Examples are: H1, H2, H3 . There are also atoms which have the same mass but are actually different elements.
Examples: Phospphorous and sulfur have the same mass number which is 32. There are also discoveries which disproved the theory that atoms can no longer be decomposed. Atoms can be distinguished by radiations.
III. SUB-ATOMIC PARTICLE
Discoveries by Rutherford, Curie. Becquerel, Plucker and others, and the results of many experiments led to the determination of the three sub-atomic particles of atoms called the electron, proton and neutron.
Crooke¡¯s tube or discharge tube was the apparatus developed by Sir William Crooke (1832-1919). Crooke passed an electric current through a gas-filled glass tube with electrodes sealed at both ends. As gas was pumped out of the tube, a pressure was reached at which the remaining gas glowed. Crooked suggested that this glow was produced by negative particles, which he called cathode rays, passing from the negative electrode (cathode) and moving toward the positive electrode (anode). The streams of small negative charge particles are called electrons.
In 1897, the English Physicist Sir J.J. Thomson measured the deflection of cathode-ray particles in both magnetic field and electric field. He determined the ratio of all of the three particles (protons, electrons, neutrons). The charge was measured by the American Physicist R. A. Millikan in 1909.
From the values of e/m and e, the mass of the electron was calculated as shown below:
e = 1.6022 x 10-19 Coulomb
e/m = change to mass ratio for electron
e/m = 1.75881962 x 1011 Coulomb/g
1.6022 x 10-19 Coulomb = 1.75881962 x 1011 Coulomb/g
Therefore mass of an electron = 1.6022 x 10-19 g
In 1886, Eugen Goldstein, a German physicist, using Crooke¡¯s tube observed that a fluorescence (in the inner surface of a cathode) was emitted from the anode and passed through the holes in the cathode. This indicates that positive rays were moving in such a tube and Goldstein called these particles as protons.
The particle has an e/m ratio of 9.5791 x 104 C/g. The absolute charge on the particle is the same as that on the electron, 1.6022 x 10-19 Coulomb. From the e/m ratio and the known value of e, the mass was calculated as 1.6726 x 10-24 grams.
The formation of positive charged particles, called ions from the molecules of gas in Crooke¡¯s tube is caused by the loss of electrons from the molecules when they are struck by high-speed cathode ray.
The existence of neutron, a particle of a mass close to that of the proton but with no charge, has been detected by English Physicist James Chadwick in 1932.
PROPERTIES OF SUB-ATOMIC PARTICLES
Particle Mass(g) Mass(amu) Relative Charge
Electron 9.1096 x 10-28 g 0.00055 amu -1
Proton 1.6726 x 10-24 g 1.00728 amu +1
Neutron 1.6749 x 10-24 g 1.00867 amu 0
1 amu = 1.6606 x 10-24 g
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