c101-lecture-1

c101-lecture-1 - 1/10/11 Chemistry Chemistry is the study...

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1/10/11 1 Chemistry Chemistry is the study of the interactions between atoms and molecules. Atoms and Molecules An atom is a particle of matter that cannot be further divided without changing the chemical identity of the atom. The word atom derives from the Greek word meaning uncuttable . Atoms are comprised of protons, neutrons, and electrons. There are ~ 115 different kinds of atoms. The different kinds of atoms are called elements. Examples of Atoms H Hydrogen He Helium C Carbon Cu Copper O Oxygen Au Gold N Nitrogen Ag Silver Na Sodium Mg Magnesium Fe Iron Cl Chlorine U Uranium Ne Neon Atoms and Molecules A molecule is a compound composed of two or more atoms. The atoms may be of the same element or of a combination of different elements. Most of the matter we see in the universe is comprised of molecules. Examples of Molecules H 2 O Water CO 2 Carbon Dioxide NaCl Sodium chloride (table salt) C 12 H 22 O 11 Sucrose N 2 Nitrogen O 3 Ozone Changes in Matter Physical Change: When a substance undergoes a physical change, its molecular identity remains the same. Chemical Change: When a substance undergoes a chemical change, the atoms in the substance are rearranged or exchanged with another substance to form new atoms or molecules.
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1/10/11 2 Physical Properties of Matter Mass Mass is an intrinsic property of an object—it is a measure of how much material is in the object. Mass and weight are not the same thing: weight is the gravitational force exerted on an object by another body (such as the Earth): w = m·g (w = weight; g = acceleration due to gravity) Physical Properties of Matter Mass (con t.) We often incorrectly refer to the mass of an object as its weight—we say we are weighing something when we are really determining its mass. You can tell if you are measuring mass or weight by the device used—any device employing a spring determines weight; any device comparing forces, such as a balance, determines mass. Physical Properties of Matter Mass (con t.) The units for mass are grams (or any multiple of grams such as kilogram, milligram, etc.) A pound is actually a unit of weight, but in common usage, we can think of it as a mass unit: 1 kg = 2.205 lbs. Mass does not change with pressure or temperature. Physical Properties of Matter Volume Volume is a measure of the space occupied by an object. Volume depends not only on the amount of material in the object, but also on the pressure acting on the object and the temperature of the object. Units of volume are length cubed: 1 cm 3 = 1 mL, 1000 mL = 1 L, etc. Physical Properties of Matter Density Density is related to what we usually refer to when we talk about something being heavy or light. Definition:
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c101-lecture-1 - 1/10/11 Chemistry Chemistry is the study...

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