Chemistry 1st Semester Exam Review

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Chemistry Exam Review : 

Michael Turner Per 6 IGCSE Chemistry Chemistry Exam Review

Matter and Change : 

Matter and Change Chemistry is the study of the composition of substances and the changes they undergo. Organic Chemistry is the study of essentially all substances containing Carbon Inorganic Chemistry largely concerns substances without Carbon Analytical Chemistry is concerned primarily with the composition of substances Physical Chemistry is concerned with theories and experiments that describe the behavior of chemicals Biochemistry is the study of chemistry of living organisms.

The Scientific Method : 

The Scientific Method The Scientific Method: is an approach to the solution of scientific problems. A proposed reason for what is observed is called a Hypothesis An experiment is a means for testing a hypothesis. A theory is a thoroughly tested explanation of why experiments give certain results. Scientific Law is a broad statement that summarizes the results of a broad spectrum of observations and experiments.

Properties of Matter : 

Properties of Matter Matter is anything that takes up space and has mass. The amount of matter that an object contains is its MASS A substance is a particular kind of matter that has a uniform and definite composition. A physical property is a quality or condition of a substance that can be observed or measured without changing the substance’s composition.

The States of Matter : 

The States of Matter A solid is matter that has definite shape and volume A Liquid is a form of matter that flows, has a definite volume, and takes the shape of its container. A Gas is matter that takes both the shape and volume of its container.

Physical Changes : 

Physical Changes A physical Change alters a substance without changing its composition. Words describing physical change include: Boil Freeze Melt Condense Break Spilt Crack Crush

Mixtures : 

Mixtures Mixtures consists of a physical blend of two or more substances. Mixtures can be homogeneous of heterogeneous. A heterogeneous mixture is not uniform in composition. One portion sampled of this mixture is not the same as another portion sampled of this mixture. A homogeneous mixture has a completely uniform composition. Salt water from the ocean is came throughout making it a homogenous mixture A solution is a homogeneous mixture. Solutions may be gasses, liquids, or solids. During Distillation, a liquid is boiled to produce a vapor that is then condensed to again to a liquid

Elements and Compounds : 

Elements and Compounds Compounds are substances that can only be separated in to simpler substances by only by chemical reaction. Substance Definite Composition Mixture of Substances- Variable Composition Element Ex: iron, carbon, Sulfur, hydrogen, oxygen Compound Examples: iron Sulfide, water Homogeneous Mixture Uniform Throughout; also called a solution Example air, tap water Heterogeneous mixture Nonuniform; district phases( Soap, concrete Matter Physically Separable

Chemical Reactions : 

Chemical Reactions In a chemical reaction, one or more substances change into a new substance. In a chemical reaction, the starting substances are reactants, and the new substances are the products. The ability of a substance to undergo chemical reactions and to form new substances constitutes its chemical properties.

Conservation of Mass : 

Conservation of Mass Combustion, or burning is an example of one of the most familiar chemical changes. When coal is burned, atmospheric oxygen combines with the carbon in the oil. The products are carbon dioxide gas, and water vapor. During Chemical Reaction, the quantity of matter is unchanged. The Law of Conservation of Mass states that in any physical or chemical reaction, mass is neither created nor destroyed.

CHAPTER 2 : 

CHAPTER 2

Chapter 2- Scientific Measurement : 

Chapter 2- Scientific Measurement Qualitative Measurements give the results in a descriptive nonnumeric form. Quantitative Measurements give results in a definite form, usually as numbers

Accuracy and Precision : 

Accuracy and Precision Accuracy is how close a single measurement comes to the actual dimension or true value of whatever is measured. Precision is how close several measurements are to the same value

Scientific Notation : 

Scientific Notation In Scientific Notation, a number is written as the product of two numbers: a coefficient of one and a power of 10! 3.6 X 104 = 10 X 10 X 10 x 10 = 36000 To multiply numbers written in scientific notation, multiply the coefficients, and add the exponents. EX: (3 X 104) X (2 X 102) = (3 X 2) X 10 4+2 Before numbers written in scientific notation are added or subtracted, the exponents must be made the same.

SIG FIGS! (Significant Figures) : 

SIG FIGS! (Significant Figures) Significant Figures in a measurement include all the digits in that are known precisely plus one last digit that is estimated. This is to allow the information that the last digit of the measurement is uncertain when others are retaining your information. The rules for determining which digits in a measurements are significant will follow this page.

SIG FIG RULES : 

SIG FIG RULES Every nonzero in a recorded measurement is significant.(ex: 24.7m, 0.743m, and 714 all have 3 sig figs) Zeros appearing between nonzero numbers are significant.(ex: 7003m, 40.79, and 1.503, all have 4 sig Figs) Zeros appearing in front of non zero numbers are not significant. (ex: 0.0071m, 0.42m, and 0.000099 m all have two sig figs. Zeros at the end of a number and to the right of a decimal point are always significant. (ex: 43.00m, 1.010m and 9.000, all have four sig figs. The zeros at the end of a measurement and to the left of the decimal point are not significant.(ex: all the zeros in 7000m, and 27210m are not significant. However if they were measured values they would be. Unlimited sig figs exist when there is counting(as if you counted 23 people in a class); the second exist when there is exact quantities involved. As when you write 60 min = 1hr or 100 cm = 1 m. Each of these has an unlimited number of sig Figs.

Sig Figs in Calculations : 

Sig Figs in Calculations In general, an answer cannot be more precise than the least precise measurement from which it was calculated. To round off a number you must first decide how many significant figures it should have. This depends on the given measurements and the arithmetic operation used to arrive at the answer. Once this is known, round off to that many digits counting from the left. If the value of the digit immediately to the right of the last significant digit in the answer is less than 5, all other digits are dropped, and the last significant digit on the answer stays the same. If the value of the digit immediately right of the last significant digit in the number is greater than 5, all other digits are dropped, and the last significant digit in the answer increases by 1.

Sig Figs in Calculations cont. : 

Sig Figs in Calculations cont. Answers to an addition or subtraction calculation should be rounded to have the same number of decimal places as the measurement with the least decimal places In calculations involving multiplication and division, answers are rounded off to the number of significant figures in the least precise term used in calculation.

The International System of Units(SI) : 

The International System of Units(SI) :is a revised version of the metric system Metric Units for length: 1km=103m m 101dm=1m ; decimeter 102cm=1m ; centimeter 103mm=1m ; millimeter 106um=1m ; micrometer 109nm=1m ; nanometer

Prefixes : 

Prefixes Mega: M :1million times larger than the unit it precedes. 106 Kilo: k : 1000 times larger than the unit it precedes. 103 Deci: d : 10 times smaller than the unit it precedes. 10-1 Centi: c : 100 times smaller than the unit it precedes. 10-2 Micro: um: 1 million times smaller than the unit it precedes. 10-6 Nano: n : 1,000 million times smaller than the unit it precedes. 10-9 Pico: p : 1 trillion times smaller than the unit it precedes. 10-12 The basic SI unit for linear measure is the meter.

Units of Volume : 

Units of Volume The space occupied by any sample of matter is called its volume. Volume of any cubic or rectangular solid can be calculated by multiplying length x width x height. A liter is the volume of a cube that is 10cm x 10cm x 10cm.

Metric Units for VOLUME : 

Metric Units for VOLUME Liter(base unit): L Milliliter: mL : 103mL=1L Cubic centimeter: 1cm3=1mL Microliter: uL : 106uL=1L

Units of Mass : 

Units of Mass Weight is a force. Weight is a measure of pull on a given mass by the earth’s gravity. The mass of an object is measured by comparing it to a standard mass of 1 kilogram(kg) A gram is 1/1000 of a kilogram and is more commonly used as a nit of mass because a kilogram is relatively large.

Metric Units for Mass : 

Metric Units for Mass Kilogram(base unit): kg :1kg=103 grams Gram: g: Milligram: mg :103mg=1gram Microgram: ug : 106ug=1g Density=mass/volume

Atomic Structure : 

Atomic Structure Democritus of Abdera first suggested the idea of atoms. Democritus said that atoms were indivisible, indestructible, fundamental units of matter. Later an English school teacher, John Dalton, came along and perfected Democritus' ideas in Dalton’s Atomic Theory. This consisted of these 4 main points

Dalton’s Atomic Theory : 

Dalton’s Atomic Theory All elements are composed of submicroscopic indivisible particles called atoms. Atoms of the same element are identical. The atoms of any one element are different of those of any other element Atoms if different elements can physically mix together or chemically combine with one another in simple whole number ratios to form compounds. Chemical Reactions occur when atoms are separated, joined, or rearranged. However, atoms of one element are never changed into atoms of another element, as a result of chemical reaction.

Electrons, Protons, and Neutrons! : 

Electrons, Protons, and Neutrons! Most of Dalton’s Theory is accepted today, other than the fact that atoms are indivisible. Atoms can be broken down into even smaller more fundamental particles. Dozens of these subatomic particles are unleashed when atoms are fractured by powerful atom smashers. Electrons are negatively charged subatomic particles. The glowing beam which travels from the cathode to the anode, is a cathode ray. The positively charged subatomic particle is called a proton. Neutrons are subatomic particle with no charge.

Continued.. : 

Continued.. Thompson discovered electrons. Thompson used the cathode ray experiment to figure that the electron is about 1/2000 of a hydrogen atom Robert A. Millikan improved this with clever experiments; this was made easier since he had accurate values for both the charge and on the ratio of the charge, to the mass of an electron. The electron carries exactly one unit of negative charge, and its mass is 1/1840 of a hydrogen atom.

The Periodic Table : 

The Periodic Table The Periodic Table is a table in which the elements are arranged according to similarities and their properties. Each column in the Periodic Table is known as groups. Each group is designated by a number-letter combination. Elements in group A are known as representative elements.

Atoms and ions : 

Atoms and ions Ions are atoms or groups of atoms that have a positive or negative charge. An ion if formed when an atom an atom or groups of atoms loses or gains an electron. A cation is any atom or group of atoms with a positive charge. Ex. Na1+ Mg2+ Anions are atoms or groups of atoms with a negative charge.

Compounds : 

Compounds A molecule is an electrically neutral group of atoms that act as a unit. Compounds that are composed of molecules are called molecular compounds. Ionic compounds are composed of positive cations and negative anions. Ionic compounds are usually formed from metallic and nonmetallic elements.

Chemical Formulas : 

Chemical Formulas A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of the substance. A molecular formula shows the number and kinds of atoms present in a molecule of a compound. Law of Definite Proportions-In samples of any chemical compound, the masses of the elements are always in the same proportions. This Law is consistent with Dalton's atomic theory The Law of multiple Proportions-Whenever two elements form more than one compound, the different masses of one element are in the ration of small whole numbers

Ionic Charges of the Elements : 

Ionic Charges of the Elements Group numbers could easily allow the charge of an element or ion to be figured out. Elements in group 1A have a charge of 1+. Elements in group 2A have a charge of 2+. Aluminum in Group 3A has a charge of 3+. Elements as N, and P, in group 5A, have charges of 3-. Elements in group 6A, as O, S, and Se, have charges of 2-. Elements in group 7A as F, Cl, Br, and I have charges of 1-. The representative groups 4A and *A usually do not form ions. The elements in group 8A rarely form compounds.

CHARGES OF THE ELEMENTS! : 

CHARGES OF THE ELEMENTS!

Polyatomic Ions : 

Polyatomic Ions Polyatomic ions are tightly bound groups of atoms that behave as a unit and carry a charge.

Naming Acids with simple Anions : 

Naming Acids with simple Anions To Name Acids with Simple Anions: (using a table of ions) The first part of the name is the prefix hydro. This is followed by a the name of the simple anion, which is shortened and - ic added for example chlorine (Cl-) would become chloric The last part of the name is the word acid

Naming acids w. Polyatomic anions : 

Naming acids w. Polyatomic anions To Name Acids with polyatomic anions: (using a table of ions) The first part of the name is the name of the anion which is shortened . One of two suffixes added to this name. - ic if the anion name ends in - ate. - ous if the anion name ends in - ite. The last part of the name is acid

Determining Formula : 

Determining Formula To determine an acid formula from a name (Using a table of ions ) we: Determine the anion present from the name. Since the compound is an acid the cation ( positive ion ) is H + Write down the formulas of the two ions . Make the value of the charge on the negative ion the subscript on the hydrogen ion Example: Sulfuric Acid sulfuric ------> sulfate --------> SO4 2- acid -------> hydrogen --------> H +1 Formula -------> H2SO4

PRACTICE QUESTIONS! : 

PRACTICE QUESTIONS! What is the difference between a heterogeneous and homogenous mixture? A- A heterogeneous mixture is not uniform in composition - A homogenous mixture is completely uniform in composition How can the various compositions of a mixture be separated? A- By physical methods as a fork to separate a taco into meet, lettuce, cheese, and tomatoes. Iron fillings can be removed from mixture by a magnet. Also by distillation(During distillation a liquid is boiled to produce a vapor that is condensed again to a liquid.

More Practice Questions : 

More Practice Questions Identify each of the following as a mixture, or a compound. Classify the Mixtures as either heterogeneous or homogeneous. Soda Candle wax Fog Ink An egg Ice Blood gasoline

Q’s and A’s : 

Q’s and A’s How do you know each of these is a chemical change?? Food Spoils A foaming antacid tablet fizzes in water A ring of soap forms around your bathtub Iron Rust A firecracker explodes

Chapter 2 Q’s and A’s : 

Chapter 2 Q’s and A’s How many significant figures are in each underlined measurements? 60s=1min -infinite number of sig figs 9 innings in a baseball game -infinite number of sig figs 1 km= 1000m -infinite number of sig figs 47.70 g of copper -4 sig figs 25 computers -infinite number of sig figs 0.0950m of gold chain -4 sig figs

More Problems!! : 

More Problems!! Round of each measurement below correctly 8.7g + 15.43g + 19 g= 47.13g -47g a. 4.32cm x 1.7cm= 7.344cm2 -7.3cm2 835.2L – 627.443L = 225.757cm2 -225.8cm2 38.742kg/0.0421= 92.02375kg -92.028kg 5.40m x 3.21m x 1.871m = 32.431914m3 -32.43m3 5.47m3 + 11m3 + 87.300m3= 103.770m3 -104m3

Questions! : 

Questions! Express each answer in scientific notation. 5.3 x 104 + 1.3 x 104= 6.6 x 104 (7.2 x 10-4)/(1.8 x 103)= 4.0 x 10-7 104 x 10-3 x 10-6= 10-5 9.12 x 10-1 – 4.7 x 10-2=4.42 x 10? (4.8x 10-5)/(2.0 x 10-2) x(6.0 x 103)=13.2 x 10-4 (5.4 x 104) x (3.5 x 109)=18.9 x 1013

Q’s and A’s : 

Q’s and A’s LIST the unit from LARGEST to SMALLEST 1 dm3 1 uL 1mL 1 L 1cL 1dL

Questions! : 

Questions! The element silver melts at 960.8 C and boils at 2212 C. Express the temperatures in Kelvins.

More Practice problems : 

More Practice problems A weather balloon is inflated to a volume of 2.2 times 103 L with 37.4 g of helium. What is the density of helium in grams per liter?

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