Physical Science Mid-Term Review 2015 Unit 1 Nature of Science and Scientific Method

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1 Physical Science Mid-Term Review 2015 Unit 1 Nature of Science and Scientific Method Notes: What is science? Science is. Observable Measureable A search for understanding Creative Testable Limited to the Natural World Open to change Repeatable Science is not Based on belief Certain/absolute Based on proof Fair Based on authority A way to explain supernatural, or other ways of knowing, such as art, philosophy or religion Pseudoscience: claims to be scientific, but doesn t follow scientific guidelines. Example: astrology Theory vs. Law: Theory: Single explanation that is supported by lots of evidence collected over a long period of time Starts as a hypothesis It can be added to or disproven Theories do not become laws, theories explain laws Example- Theory of Evolution, Theory of Plate Tectonics Law: Prediction of what describes a pattern in nature Describes how something behaves, formula that tells us what things will do A truth that is valid everywhere in the universe It does not provide any explanations like a theory does Not all scientific laws have accompanying explanatory theories. Example- Gravity is an example of a scientific law because no experiment has been done to disprove it. Steps of the Scientific Method 1. Make an observation. 2. Ask a question (what s the problem?) / Do research. 3. Form a hypothesis 4. Test your hypothesis Experimentation 5. Collect data / Results 6. Analyze and Conclude 7. Repeat Step 1: Observation vs. Inference What is an observation? Definition: describing something using your senses, computer tools, research

2 What is an inference? Definition: logical prediction based on an observation Step 2: Question / Do research How can you do research? Examples: Computer Interviews Library Periodicals Step 3: Form a hypothesis What is a hypothesis? Prediction based on prior knowledge and creativity NOT an edeucated GUESS! Usually an If.then. statement Testable! Step 4: Test Experiment! What materials do I need? What is my procedure? Should be written in list format, like a recipe. Someone else should be able to copy your experiment based on your procedures. Variables Independent variable (IV): what you or the tester changes Dependent variable (DV): what you are measuring Control Group: a neutral point of reference to compare data against.the normal. Not required for every experiment. Constants: variables that remain the same. Example: amount of water and sunlight I give my plants when I m testing which fertilizer makes them grow best. I give my plants all the same amount of water and sunlight. Example 1 Identify the IV, DV, control and constants for the following: You decide to clean the bathroom. You notice that the shower is covered in a strange green slime. You decide to try to get rid of this slime by adding lemon juice. You spray half the shower with lemon juice and spray the other half with water. After 3 days of spraying equal amounts 3 times a day, there is no change in the appearance of green slime on either side of the shower. IV? DV? Control group? Constants? Example 2 Identify the IV, DV, control and constants for the following: Marissa wanted to find out if the color of food would affect whether kindergarten children would select it for lunch. She put food coloring into 4 identical bowls of mashed potatoes. The colors were red, green, yellow and blue. One bowl of mashed potatoes was left as the regular white color. Each child was able to choose which color they wanted. Each day she recorded the choice of 100 different students. She did this for 5 days.

3 IV? DV? Control group? Constants? Step 5: Collect Data / Results What kinds of data do I collect and how do I define them? Quantitative: a number, measureable, countable Qualitative: description Examples: Quantitative: The U.S. Flag has 50 stars on it and 13 stripes. Qualitative: The U.S. Flag is red, white, and blue. Step 5 continued: Organize data How can I organize my data? Table Graph (dependent variable: y-axis, independent variable: x-axis How do I know when to use a certain kind of graph? Line: Comparing 2 variables Bar: Comparing Quantitative vs. Qualitative data, bars don t touch Pie/Circle: Showing proportions of a whole or percentages Histogram Frequency distribution---bars touch Step 6: Analyze and Conclude Analyze data: What are graphs actually telling you? Does data support or reject your hypothesis? Conclusion: Summarize your results. Answer your question. Was your hypothesis supported? What could you change for next time, to make your experiment better, more valid? If your hypothesis isn t supported, how would you change it or revamp your experiment? What future research would you do? Step 7: Repeat All scientific experiments must be repeatable. They are subject to peer review and others must be able to perform your experiment and repeat your results.

4 Unit 2: Composition and Properties of Matter Review Elements, Compounds, Mixtures and Physical/Chemical Properties and Changes Notes: Vocabulary: Matter: has mass and takes up space (pure substances and mixtures) Pure Substances: composition definite, elements and compounds Elements made up of 1 kind of atom can t be broken down into a simpler substance on the periodic table example: oxygen, copper, iron Compounds two or more elements chemically combined, example: NaCl (sodium and chlorine = salt). Often ends in ide Have a definite and fixed ratio, in water there are 2 hydrogens and 1 oxygen (H2O) Compound has different properties than the elements its made of. Ex: NaCl, Sodium or Na is a metal, while Chlorine is a poisonous gas but when chemically combined, they form salt which we eat! Mixtures: composition variable (homogeneous or heterogeneous).

5 Mixtures are formed simply by blending two or more substances together in some random proportion without chemically changing the individual substances in the mixture. Mixtures can be separated because they are only physically bonded, not chemically bonded. Mixtures can then be broken down into homogeneous and heterogeneous. A homogeneous mixture or solution: these are well mixed, where you can t see the particles and they have a constant composition throughout. o Examples: salt-water, kool-aid, air we breathe, alloys (metal mixtures), o Can be two gases (air), two liquids, gas in liquid (carbon dioxide in soda), solid in liquid (salt in water), or two solids (an alloy, gold and copper) o Solute: the substance being dissolved o Solvent: the substance doing the dissolving. Water is a polar molecule (positive on one end and negative on the other) and is known as the universal solvent. o Non-polar solvents are toxic, flammable and generally dangerous. o Colloid: a type of mixture with larger particles, but they are not heavy enough to settle out. A way to detect a colloid is that you can see light scatter through them. (in regular solutions, you can t see light through them). Examples: milk, fog, Jell-O The scattering of light by colloids is called the Tyndall Effect. A heterogeneous mixture: These have areas with differing compositions, and are not wellmixed (you can usually see the separation of the different substances). o Examples: salt with sugar (no water), water with gasoline or oil, salad, trail mix, stew, Raisin Bran cereal o Suspension: a heterogenous mixture containing a liquid in which visible particles settle. Example: Pond water, orange juice with pulp Some ways to speed up the rate of dissolving in most solutions: Stirring Temperature **the exception to these rules are if you are dissolving a gas in a liquid. Gases dissolve faster if a liquid is cooled. Some ways to separate mixtures: Evaporation Distillation Centrifuge Filter/sort Magnetism

6 Physical and Chemical Properties/Changes Physical Property (a characteristic of a material that you can observe without changing the identity of the substances that make up the material) Chemical Property (characteristic of a substance that indicates whether it can/cannot undergo a certain chemical change, anything that has to do with a reaction or inability to react) Color Density Flammable/Combustible Shape Boiling point Reaction to light Size Freezing point Corrosive Volume Solid/liquid/gas Reaction to vinegar, acid, oxygen any type of ability to react or not react Physical Change (no changes occur in the structure of the atoms or molecules composing the matter. The substance is still the same substance as it was before the physical change occurred) Rip/ tear/ cut Change in state (from liquid, gas or solid) Chemical Change (rearrangement of bonds between the atoms occurs. This results in new substances with new properties). Burning Color change Boiling Rusting Stretching / Freezing React with something folding Mix Melting **Some indicators of a chemical change are smell, burning, bubbles.but the only way to be sure a chemical change has occurred is if a new substance is formed. How does temperature affect chemical changes? Increasing the temperature will cause chemical changes to occur faster. Decreasing the temperature will cause chemical changes to occur slower. Law of Conservation of Mass: Matter: has mass, and takes up space Mass: amount of matter in an object Law of conservation of mass: matter, during a chemical change, can neither be created nor destroyed, it just changes form. Also applies to a physical change, since during a physical change matter is neither being created or destroyed, it may just look different. Water and Carbon Cycles: Biogeochemical cycles:

7 The Carbon Cycle: The carbon cycle is a complex biogeochemical cycles, where carbon moves by various processes through different reservoirs. In the above picture, the process represented by the letter A is respiration. Respiration is where carbon dioxide leaves plants or animals and enters the atmosphere. B represents the process of photosynthesis, where plants take in carbon dioxide to aid in the process where they can make sugars, or food. C represents a process called decay, where organic matter is broken down by tiny microbes and released as carbon into the geosphere, and/or the atmosphere. Humans are affecting the carbon cycle in two major ways. The first is through land use. When we destroy forests of trees, this upsets the carbon flow in that area. The same thing is happening when we build massive buildings and parking lots, destroying natural vegetation. The second is through the burning of fossil fuels. We are digging up organic material that took millions of years to form, and burning it to provide energy for us. The Water Cycle: The water cycle is how water moves through all the various areas of the Earth. The water cycle consists for five main components: evaporation, condensation, precipitation, transpiration, and runoff. Because of the water cycle, it is true that the water we have today has been around for a very long time. It simply continues to get cycled through earth s atmosphere and bodies of water. Unit 3 States of Matter (kinetic molecular theory, heat and phase changes) 4 Basic types of matter: Solid: Particles are tightly compact, vibrate but can t move around (low Kinetic energy - KE), definite shape and volume Liquid: Particles are still close together, but can move around (higher KE), No definite shape, but definite volume Gas: Particles can easily spread out or move close together, particle move freely and with a lot of energy (high KE), no definite shape or volume Plasma: Very high KE; particles collide with enough energy to break into charged particles (+ / -), Gas-like, indefinite shape & volume, this form is not too common on Earth, however it is the most common form of matter in the universe, Examples: stars, florescent and neon lights, lightning. Kinetic Molecular Theory (KMT)

8 Tiny, constantly moving particles make up all matter. The kinetic energy (motion) of these particles increases as temperature increases. These particles are colliding with each other and the walls of their container (creates pressure). Define Heat : movement of thermal energy (energy inherent to an object) from a substance at a higher temperature to another substance at a lower temp Three kinds of heat transfer. a. Conduction transfer of heat energy from one particle to another by direct contact. (Primarily in solids) b. Convection transfer of heat energy in fluids-gases and liquids) through the bulk movement of matter from one place to another. (Produces currents) c. Radiation transfer of energy through electromagnetic waves. (Matter is not required!) (Radiant & infrared radiation from the sun) What happens when you put ice in a warm soft drink? The heat energy moves from the soft drink into the ice by conduction (particle to particle contact) causing the kinetic energy in the molecules of ice to increase, which makes the ice melt. Pressure: Pressure = Force / Area. Pressure is created by molecules colliding with each other and the walls of their container. Pressure can be affected by volume, temperature, and number of molecules. Boyle s Law: Volume of a confined gas is inversely proportional to the pressure exerted on the gas (as pressure is increased, volume is decreased at the same rate and vice versa) This is true as long as temperature is constant Charles Law: Volume of a gas increases with increased temperature. (Gases expand with heat). Volume and temperature are directly proportional meaning they increase or decrease together at the same rate.

9 Phase Changes: When matter turns from one form to another (example, water, a liquid freezing turning to ice, a solid). Structure of the Atom Unit 4 - Atoms Matter is anything that has mass and takes up space. Atoms are the smallest units of matter that something can be divided into while still retaining its properties. Atoms are made of main particles, called sub-atomic particles. They are protons, neutrons, and electrons. Protons: Neutrons: Electrons - positive charge - no charge (neutral) - negative charge - in the nucleus - in the nucleus - outside the nucleus, - is = to the atomic number - contributes to the atomic mass in a cloud - contributes to the mass - atomic mass protons = neutrons - insignificant mass - **determines the element - **determines isotopes - in neutral atom = the number of protons - forms bonds - *when electrons leave or join an atom, ion is formed Nucleus: center of the atoms, made of protons and neutrons Atomic Mass Unit (amu): a proton and a neutron each have a mass of 1 amu

10 ***Mass Number = protons + neutrons (will ALWAYS be a whole number, no decimals) ***Atomic Mass = the mass on the periodic table, the average of all the isotopes of an element, will have a decimal point. Ions: an atom or molecule where the total number of electrons is not equal to the total number of protons, giving the atom a positive or negative overall charge. ***So, whenever protons electrons, you have an ion. An ion is only created when electrons leave or join an atom nothing to do with protons leaving or joining. Acids and Bases: A measure of Hydrogen ions (H+). Acids have more Hydrogen ions. We measure them using a ph (potential Hydrogen scale). The scale ranges from 0 14, where 0 is a strong acid, 7 is neutral and 14 is a strong base. Forces In the Atom 1. Gravitational Force Attraction of objects due to their mass a. Depends on the distance and masses of the objects b. Weakest Force 2. Electromagnetic Force a. Like Charges repel b. Unlike charges attract c. Responsible for keeping the electrons around the nucleus 3. Weak Nuclear Force a. This force plays a key role in the possible change of sub-atomic particles. b. The force responsible for radioactive decay

11 4. Strong Nuclear Force a. Holds the atomic nucleus together b. Counteracts the electromagnetic force. Periodic Table: 1. Groups: Vertical columns of elements with similar properties Numbered 1 18 Elements in same group, have the same number of electrons in outer energy level (valence electrons) Example: Every element in group 1, has 1 electron in its outer shell, every element in group 2, has 2 electrons in its outer shell, and so on (excluding transition metals) ****Remember: Valence Electrons are electrons in the last shell or energy level of an atom Important because: Determine an elements ability to bond with another element Chemical properties depend almost entirely on the configuration of the outer electron shell (reactivity, flammability, etc.) Periods: Horizontal rows of elements that contain increasing numbers of protons and electrons Numbered 1 7 Each row in a period ends when an outer energy level is filled Example: Every element in the top row has 1 orbital for its electrons, 2 nd row has two orbitals and so on

12 Categories of elements in the periodic table: Alkali Alkaline Earth Transition Metals Basic metal Semi metal Non-Metal Halogens Noble Gas Lanthanide (rare-earth) - radioactive Actinides (rare-earth) - radioactive 3 Main Categories (you have to know!!!!) Metals: Good conductors of heat and electricity All but Mercury are solid at room temp ***Metals are located to the left of the stair step Alkali Metals (Group 1) are the most reactive of all metals; don t occur in nature in their element form Alkaline Earth Metals (Group 2) shiny, ductile and malleable; combine readily with other elements Transition Metals (Group 3 12) most familiar metals because they often occur in nature uncombined Inner Transition Metals Lanthanide Series elements with atomic # Actinide Series elements with atomic # Non-Metals: Elements that are: usually gases or brittle solids at room temp, are poor conductors ***located to the right of the stair step Noble gases (Group 18) exist as isolated atoms. They are all stable because the outer energy level is filled. Metalloids: ***Elements that make up the stair step Have metallic and non-metallic properties (share characteristics with metals and non-metals)

13 Part of the mixed groups (groups 13, 14, 15, 16 and 17) which contain metals, non-metals and metalloids How to read the periodic table: (KNOW THIS)