Chemistry 208 All QUIZ Essay

The Scientific Method Step 1: Performing Experiments Step 2: Making Observations Step 3: Proposing a Hypothesis Step 4: Confirming the Hypothesis Step 5: Proposing a Scientific Law Scientific Notation It is a mathematical expression in which a number is expressed as N x 10^n where N contains only one nonzero digit to the left of the decimal and n is an integer. Rules for Determining Significant Figures (digits) -All nonzero digits are significant figures -Counting begins from the left with the first nonzero number -Zeros between nonzero digits are counted as sig. Figures -Terminal zeros (zeros to the right of the right of a number) are always significant if the value contains a decimal point. Ex: 2. 3700 g: 5 significant figures 17. 50 mL: 4 significant figures Rule 1- In calculations involving measured values (with a certain # of sig. figs), the number of sig figs in the final answer depends on the operation performed. Rule 2- In multiplication and division of measured quantities, the final answer contains the same number of sig figs as are in the measurement with the least number of sig figs. Rule 3- In the final answer of a calculation involving exact numbers, unit conversion factors and constants, the number of significant figures is dictated by the measured quantity involved. Density = Mass/ Volume Matter: The term matter is used to describe things that occupy space and are perceivable by our senses. It can be classifies in terms of its physical state or chemical composition. Elements: composed of one type of atom. Classified as a metal, nonmetal or metalloid. Compound: a combination of elements in a definite proportion. Atoms of each individual elements are chemically combined to form the compound. A chemical change can break down a compound into its individual elements. Mixture: a non-pure substance made of 2 or more elements or compounds that can be separated by physical procedures. Protons have a positive charge, found in the nucleus. Neutrons have no charge, found in the nucleus. Electrons have a negative charge. The atomic number of an element is equal to the number of protons in the nucleus of its atoms. The mass number is equal to the number of protons and neutrons in the atom. To calculate the number of neutrons, subtract the atomic number from the mass number. Molecules are a combination of atoms in a definite proportion e. g. , molecule of water Ions are charged species formed by loss or gain of electron(s) from an atom. Loss of electron – cation (positively charged) Gain of electron – anion (negatively charged)