1st Nine Weeks Chemistry Study Guide PDF 2024-2025

Physical Science – Chemistry 1st Nine Weeks Study Guide SCIENTIFIC METHOD The experiment is the foundation of the scientific method, which is a systematic means of exploring the world around you. Although some experiments take place in laboratories...

Physical Science – Chemistry 1st Nine Weeks Study Guide SCIENTIFIC METHOD The experiment is the foundation of the scientific method, which is a systematic means of exploring the world around you. Although some experiments take place in laboratories, you can perform an experiment anywhere, at any time. And when conducting an experiment, one should not consider the scientist's biases. Bias is a specific perspective or outlook on a topic that is often based on personal beliefs or experiences. Steps of the scientific method: 1. Make observations (Collect information using your senses and ask questions) a. An inference is what you decide about an observation. Inferences attempt to explain or interpret observations based on the evidence and/or our experience. b. A prediction is an educated guess about a future event. A prediction may or may not happen, but it should be logical. 2. Research 3. Formulate a hypothesis a. A hypothesis is an educated guess, based on observation. It is a prediction of cause and effect. Usually, a hypothesis can be supported or refuted through experimentation or observation. A hypothesis can be disproven, but not proven to be true. b. What one thing will I change on purpose? Scientists call this the independent variable (manipulated.) c. How will I know if one thing changed on purpose made any difference? Scientists call this the dependent variable (responding.) d. What things will need to keep exactly the same? Constants 4. Design and conduct an experiment to test the hypothesis a. An experiment is a procedure carefully done to examine the validity of a hypothesis. b. An experimental group is the group that receives the variable being tested in an experiment. c. The control group is the group in an experiment that does not receive the variable you are testing. A control is something used as a standard of comparison for checking the results of an experiment. d. A controlled variable (constant) is something that is kept the same in an experiment. e. A variable is a number or feature that is changeable - that can have lots of different possible values. 5. Data Collection (Data are pieces of information collected before, during, and after an experiment. It is important to keep detailed notes and to record all data collected throughout the scientific inquiry process so that it can be analyzed to determine results and referenced to support the conclusions.) a. Types of data i. Quantitative is based on numerical data, which can be analyzed using statistics. This type of research focuses on pinpointing what, where, when how often and how long social phenomena occur. ii. Qualitative is based on data that cannot be measured or counted but can be collected and interpreted through observation. b. Sometimes data make more sense in a graph or as a picture. i. There is a standard way to graph the data, with the independent variable on the x-axis and the dependent variable on the y-axis. 1. Direct relationship if when one increases so does the other or as one decreases so does the other. 2. Inverse relationship if when one increases the other decreases or as one decreases the other increases. ii. Picture/Model (Scientists often construct models to help explain complex concepts.) 1. These can be physical models, like a model volcano or atom or conceptual models, like predictive weather. 6. Analysis (Scientists make sure that they collect accurate data so their results will be trustworthy. Unfortunately, not all data in science experiments is of the same quality. Some people are better at measuring things than others, and sometimes there can be issues that cause all your data to be off by a certain amount.) a. The accuracy of data tells you how close to being correct your data is. b. The reproducibility, or precision, of data tells you how close together your measurements are. 7. Evaluate the results of the experiment / Accept or reject the hypothesis a. In addition to carefully collecting data in a controlled experiment, scientists must repeat an experiment multiple times to ensure they can obtain the same results each time before those results are considered reliable by the scientific community. 8. If necessary, make and test a new hypothesis. Catalano 2024-2025  Over the course of time, a collection of hypotheses can be used to generate either a scientific law or theory. 1. A scientific law is a statement that summarizes a collection of observations or results from experiments. Scientific laws are always true under the same conditions and therefore can be used to make predictions. Examples of laws: a. The Law of Conservation of Mass b. Newton's Law of Universal Gravitation c. Bernoulli's Principle 2. A theory, or model, is also based on a set of hypotheses. Unlike the law, however, a theory describes and explains why a natural phenomenon occurs. In science, theories explain reality well and are generally accepted as truth. Theories are based on information from many different areas of study. Theories let scientists make testable predictions. Theories can also be changed or modified if new evidence is found! Examples of theories include: a. Cell Theory b. Atomic Theory c. Plate Tectonics Theory SCIENCE LAB PROCEDURES The science lab is an inherently dangerous place, with fire hazards, dangerous chemicals, and risky procedures. No one wants to have an accident in the lab, so it is imperative to follow lab safety rules. Review the SCIENCE LAB RULES found in your folder. Several types of equipment are required for any functional laboratory to operate properly. Be it a school, research, or a medical laboratory, special equipment is required. Review the LAB EQUIPMENT names and their uses. (Also found in your folder.) MATHEMATICS IS THE LANGUAGE OF SCIENCE When you do scientific experiments that involve measurements, your results may fit the trend that is expected. However, it is unlikely that the numbers will turn out exactly as expected. In an experiment, you often make a prediction about an event’s outcome but find that your actual measured outcome is slightly different. 1. The percentage error (% Error) gives you a means to evaluate how far apart your prediction and measured values are. Percent error is calculated as the absolute value of the difference between the predicted and measured values divided by the true value multiplied by 100. a. Remember that with percent error, smaller is better. A perfect outcome would have zero percent error. In the late 1700's, as scientists began to develop the ideas of physics and chemistry, they needed better units of measurements to communicate scientific data more efficiently. Scientists needed to prove their ideas with data based on measurements that other scientists could reproduce. Today this decimal system is known as the SI system, or metric system. Scientists all use the same system of measurement to make the sharing of information easier. 1. The SI system of measurements is based on the metric system which uses seven base units. a. Length (meters) e. Temperature (Kelvin) b. Mass (grams) f. Luminous Intensity (lumens) c. Time (seconds) g. Amount of Substance (moles) d. Electric Current (Amperes) 2. Prefixes are used to show very large or very small quantities of length, mass, or volume. In mathematics, especially as it relates to the sciences, there are often numbers that are very large or very small, and they can be difficult to work with. By writing these numbers in scientific notation, we can more easily solve problems with numbers that used to be too big or too small. 1. Scientific Notation is used as a shorthand way to represent either very large or small numbers. a. The first number is called the coefficient. It must be greater than or equal to 1 and less than 10. b. The second number is called the base. It must always be 10 in scientific notation. The base number 10 is always written in exponent form. ▪ Example: 0.0000006782 is written in scientific notation as 6.782 x 10 -7 c. Be able to convert numbers from standard notation to scientific notation, scientific notation to standard notation and do calculations on a calculator with numbers that re in scientific notation. Catalano 2024-2025 Even though the United States adopted the SI system in the 1800’s, most Americans still use the English system (feet, pounds, gallons, etc.) in their daily lives. Because almost all other countries in the world, and many professions (medicine, science, photography, and auto mechanics among them) use the SI system, it is often necessary to convert between the two systems. 1. Dimensional analysis is a way to find the correct label (also called units or dimensions) for the solution to a problem. In dimensional analysis, we treat the units the same way that we treat the numbers. a. The goal of dimensional analysis is to simplify a problem by focusing on the units of measurement(dimensions). b. Dimensional analysis is very useful when converting between units (like converting inches to yards or converting between the metric and English systems of measurements). c. Be able to convert among different units using dimensional analysis Significant Examples Digits 7.987 4 Significant Figures are the number of figures in an answer that are known with certainty. 7.98 3 Significant figures are used to express how precision of a measurement. Be able to identify, count and round to a specified number of significant digits. 7.9 2 8. 1 8.0 x 10 23 2 Density (You should memorize the equation.) 1. Density is defined as the ratio between mass and volume or mass per unit volume. It is a measure of how much stuff an object has in a unit volume (cubic meter or cubic centimeter). 2. Mass is a measure of how much stuff an object contains 3. Volume is the measure of how much space an object occupies in three-dimensional space. We can use the water displacement method to find an object's volume, because the volume of displaced water, or water that is pushed out, is equal to the volume of the object. o A meniscus, the downward or upward curve at the surface of a liquid in a container, occurs because of surface tension in the liquid and must be read at eye level. For a concave meniscus, the correct volume will be read at the bottom of the curve. 4. Know how to solve density problems and know the units used in solving density. 5. Know the density of water is 1 g/cm3. 6. Know how to find the volume of a liquid, regular-shaped object, and irregular-shaped object (displacement method). 7. Know that mass and volume have a linear relationship with density. Which is one were increasing or decreasing one variable at a time will cause a corresponding increase or decrease to the other variable. HISTORY OF THE ATOM (Atoms are the building blocks of all matter.) Democritus (4th century B.C.)- Greek philosopher proposed idea of small “atomos” John Dalton (early 1800’s) - English schoolteacher uses experiments & scientific method (billiard ball model) Atoms are indivisible (cannot be subdivided) - we now know they can be split apart All atoms of the same element are exactly alike- we now know about isotopes Atoms of different elements join in small whole number ratios to make compounds (molecules). Ernest Rutherford (late1800’s) discovers atoms have a positively charged nucleus w/ protons and mostly empty space – alpha particles passed through (Gold-foil experiment) Max Planck- Quantum Theory: energy is not emitted constantly, but in small packets called quantum Henry Mosley-used x-ray experiments to discover the atomic number of an element J.J. Thomson (early 1900’s) discovers negatively charged electrons using a cathode ray tube. (“Plum pudding” model) Neils Bohr (1913) discovers that electrons exist in different energy levels outside the nucleus (Planetary Model) Catalano 2024-2025 Modern Atomic Theory Schrodinger -Electrons exist in “clouds” (most likely locations of electrons in atoms)-electrons behave like waves not particles. Heisenberg - The electrons’ position is nearly impossible to determine; this model only describes the probability of the election’s position. James Chadwick- discovered the neutron Albert Einstein- Theory of Relativity: energy and mass are equivalent and can be transformed into each other. In other words, energy is released as matter is destroyed, and matter can be created from energy. (E=mc 2 – energy = mass x speed of light squared) Know the properties of light (behavior) – wave and particle (packet of energy) How does an atom emit light? (ground state/excited state) ATOMIC STRUCTURE Chemistry- the study of matter and the transformations it can undergo. Atomic number- a count of the number of protons in the atomic nucleus Atomic mass- the mass of an element’s atoms listed in the periodic table as an average value based on the relative abundance of the element’s isotopes. Mass number- the sum of the number of protons and neutrons in an atom Isotopes-members of a set of atoms of the same element whose nuclei contain the same number of protons but different number of neutrons. Element- any material that is made up of only one type of atom Compound- a substance containing atoms of two or more different elements chemically bonded together. Neutral atoms that have no electric charge have the same number of electrons and protons. o An atom that gains or loses an electron is called an ion. o An atom that gains an electron becomes negative – called anion. o An atom that loses an electron becomes positive – called cation. Know the particles that make up an atom (including the atomic nucleus), their charges, mass, and location within the atom. (see below) Particle Electrical Charge Relative Mass (amu) Location in the Atom Proton Positive (+1) 1 Nucleus Neutron Neutral (0) 1 Nucleus Electron Negative(-1) 0 Energy “cloud” outside nucleus 1. Know how many protons, neutrons, and electrons an atom has, given its symbol, atomic number, and mass number. 2. Be able to represent isotopes by name and symbolically (Hydrogen-1 and 21𝐻 ) 3. Remember, generally speaking, the isotope with the mass number closest to the atomic weight will be the most abundant. 4. amu - atomic mass unit-special unit developed for atomic masses 5. The atomic mass is not given as a whole number because it is a weighted average taken of all of an atom's isotopes found in nature. 6. Know how to calculate the average atomic mass (mass of isotope #1 x abundance of isotope #1) + (mass of isotope #2 x abundance of isotope #2) + … …. 100 Catalano 2024-2025 THE PERIODIC TABLE Dmitri Mendeleev- 1st to arrange elements in 7 groups with similar properties. He discovered that the properties of element “were periodic functions of their atomic weights”. Henry Moseley- his work was used to reorganize the periodic table based upon atomic number instead of atomic mass. The periodic table follows the Periodic Law, which states that the physical and chemical properties of the elements recur in a systematic and predictable way when the elements are arranged in order of increasing atomic number. Organization: Arranged in increasing atomic number (number of protons) Periods are the horizontal rows (there are 7 periods) Groups are the vertical columns (there are 18 groups) o Groups 1, 2, 13-18 are called Representative Groups (Main Block) o Groups 3 – 12 are called the Transition Element Group 1 2 3-12 (Groups) 13 14 15 16 17 18 periods 1 + 2 + 3 + 4 +/- 3- 2- 1- 0 1 H He Transition Metals 2 Li Be B C N O F Ne (outer transitions metals) 3 Na Mg Al Si P S Cl AR 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og Inner Transition Metals 6 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 7 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr GENERAL CHARACTERISTICS OF METALS, NONMETALS, AND METALLOIDS Metals: found on the left side of stair step on the periodic table; good conductors of heat and electricity, high density (usually), high MP and BP (usually), hard, shiny, malleable (can be pounded into sheets), ductile (can be drawn into wires) and most metals are solid at room temperature Nonmetals: found on the right side of stair step on the periodic table; brittle, poor conductors of heat and electricity, low density, low MP and BP (many are gases) Metalloids (semimetals): metalloids occur along the diagonal stair-step line that distinguishes metals from non-metals; some metalloids are shiny (silicon), some are not (arsenic), tend to be brittle, as are nonmetals, tend to have high MP and BP like metals, tend to have high density, like metals. Metalloids are semiconductors of electricity – can conduct heat and electricity under certain conditions. This makes them good for manufacturing computer chips. Know the location of the metals, metalloids and nonmetals Know the location of the alkali metals, alkaline-earth metals, transitions metals, halogens, noble gases Know the location and number of the groups and periods on the periodic table The period number of an element signifies the highest unexcited energy level for an electron in that element. Catalano 2024-2025  Families (Groups) of Elements Groups Name of Group Characteristics Most reactive metals because of one valence electron, form +1 ions; located on the left 1 Alkali Metals side of the PT; usually solids 2 Alkaline Earth Metals reactive because of two valence electrons, form +2 ions 3-12 Transition Metals common metals that can form +2 or +3 ions 13-16 Other Metals, Metalloids, Nonmetals usually form +3,+/-4, -3, or -2 ions also known as the salt forming group; most reactive nonmetals; they need one valence 17 Halogens electrons, form -1 ions 18 Noble gases Do NOT form ions because their outer shell of electrons is full; they are said to be inert. Valence Electrons and Group Number 1. Valence electrons are important in determining how an element reacts chemically with other elements. 2. Know that 8 electrons (octet rule) are needed for an atom to become stable. (Hydrogen/Helium needs 2) Representative Groups (Main Block) (1, 2, 13-18) have the same number of valence electrons as the last number of their group: Group 1 has 1 valence electron. Group 2 has 2 valence electrons. Group 13 has 3 valence electrons. Group 14 has 4 valence electrons. Group 15 has 5 valence electrons. Group 16 has 6 valence electrons. Group 17 has 7 valence electrons. Group 18 has 8 valence electrons. (With the exception of He only has 2.) Ions are formed when one element’s atoms chemically react with another element’s atoms to form compounds. Group 1 elements lose one valence electron to form +1 ions Metals Group 2 elements lose two valence electrons to form +2 ions Group 13 elements lose three valence electrons to form +3 ions Group 15 elements gain three valence electrons to form -3 ions Nonmetals Group 16 elements gain two valence electrons to form -2 ions Group 17 elements gain one valence electrons to form -1 ions Know the following trends The properties of the elements across a period change from metallic to nonmetallic. Electronegativity can be understood as a chemical property describing an atom's ability to attract and bond with electrons. This is because the number of protons in the atomic nucleus increases. The number of valence electrons increases across a period. Ionization energy is the energy required to remove an electron from an atom. Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. However, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases. Catalano 2024-2025