“Rule #31: always check the back seat.” Zombieland
8th Grade Final Exam REVIEW
1. Explain the difference between a solid, liquid, and gas in terms of molecular energy. Draw a picture of CO2 as a solid, liquid, and gas. Use arrows to show molecular movement. Solid’s have the least molecular energy (their molecules move the least amount) while gas has the highest molecular energy (their molecules move the most).
2. Molecular bonds are stored (potential) energy. Explain how energy is stored or released in the formation and breaking of chemical bonds. Discuss how this relates to the amount of energy needed to melt water versus freeze water. It requires energy to break bonds, and energy is released when bonds are formed. For example, large complex molecules like glucose can be broken and reassembled into large numbers of small molecules to release energy (there are less bonds in large molecules then in lots of small molecules). Solids form when weak attractive forces form weak bonds between molecules, therefore energy is released when solids form (i.e. you make it cold). The same amount of energy released in the formation of a solid can be added to a solid to cause melting/cause the attractive bonds to break (i.e. you add heat/energy to make things melt).
3. Discuss what this graph shows about a chemical reaction. Give an example of a simple chemical reaction that may have a graph like this one. This graph shows an exothermic reaction (energy exiting the system). An example of this would be burning paper. The amount of energy available at the start of the reaction is higher then the amount of energy after the reaction (energy was released). The highest point of the graph is much higher then room temperature, therefore this reaction would not begin with the energy available at room temperature (i.e. a spark would be necessary for the reaction to begin). Another example of this reaction would be cellular respiration (or any large molecule being broken and rebuilt into lots of smaller molecules).
4. Using your understanding of Greek and Latin prefixes, explain the meaning of the prefix endo and exo. Endo=to enter, to add to the system. Exo= to exit, to subtract from the system.
5. Explain what happens when electrons are excited. When electrons are excited the move from their normal low energy orbit to a high energy orbit. Because the high energy orbit is unstable the electron will “fall” back to it’s normal low energy orbit. This can be seen as a color change (for example fireworks), electron spectrum, fluorescence, light emission.
6. Explain how energy can be transferred and transformed. Energy is transferred from potential to kinetic to potential, etc. Energy is transformed from one form to another between mechanical, thermal, electric, chemical, nuclear, and electromagnetic.
7. Define: compound, element, atom, mixture. Atom= smallest unit of matter. Element= a single type of atom, ex: H2, Fe, etc. Compound=two or more types of atoms chemically bonded together, ex: CO2, H2O, C6H12O6, etc. Mixture= two or more compounds or elements physically mixed together ex: gravel, salt water, air, etc.
8. Name the following compounds: CaO, MgF2, CO2, C6H12O6 Calcium oxide, magnesium fluoride, carbon dioxide, glucose
9. Write the correct formula for the following compounds: Carbon monoxide, lithium chloride. CO2, LiCl (remember the difference between capital letters and lower case letters when writing the symbols for the elements.)
10. Mixtures with a lot of solutes (dissolved stuff) will freeze at higher or lower temperatures then the pure liquid? Mixtures with a lot of solutes will boil at higher or lower temperatures then the pure liquid? Lots of solutes have lower freezing points and higher boiling points. This is called freezing point depression and is why we add salt to roads to melt ice, and boiling point elevation and why we add salt to water when we boil pasta.
11. Describe how density can create layers in a liquid or gas. Compounds with low densities will rise or float above compounds with high densities. This is why the atmosphere has layers (low density high up, high density near ground) and why it is easier to float in salt water then fresh water.
12. Describe how an atom becomes an ion. Be specific using the atom Magnesium as an example. Atoms become ions by gaining or losing their valence electrons. Remember that the octet rule says that all atoms (except hydrogen and helium) want either 8 or 0 valence electrons. The group number on the period table corresponds to the number of valence electrons. Magnesium is in group 2; it is easier to lose 2 electrons to have 0 electrons then it is to gain 6 electrons to have 8; therefore, Mg will lose two electrons to become an ion with a +2 charge. DON’T forget- LOSING electrons is LOSING NEGATIVENESS to become more positive!!!! (it’s backward logic, but remember, you are trading negative charges)
13. Diagram an atom; include the nucleus, electron cloud, electrons, protons, and neutrons.
14. Use the periodic table to determine the number of protons, neutrons, and electrons and valence electrons in a sodium atom. The periodic table tells us that sodium (Na) has an atomic number of 11, which means that Na has 11 protons. The periodic table tells us that Na has an atomic mass of 22.9; the closest whole number is 23 so 23-11 (the number of protons)= 12 which is the number of neutrons. The periodic table tells us that Na is in group 1 so it has 1 valence electron and therefore loses 1 electron to become an ion with a +1 charge.
15. Describe how the periodic table is arranged. Which atoms share similar properties? The periodic table is arranged by order of increasing number of protons/increasing atomic number. Elements in the same column share reactive properties, have the same number of valence electrons, and take the same charge as an ion. Elements in the same row have increasing atomic mass and atomic number and have valence electrons in the same energy level.
16. Balance the following reaction: C6H12O6 + 6O2 à 6CO2 + 6H2O
17. Compare and contrast: chemical properties vs. physical properties, chemical changes vs. physical changes. Give examples of all four of these words.
Describes / examples / change / examplesPhysical properties / Physical characteristics / Size, shape, state / Physical changes change the look of the matter without changing what the chemical is. / Melting, freezing, cutting, breaking, etc
Chemical properties / Chemical behavior / Flammability, corrosive, tarnishing / Chemical changes change the type of chemical you have, i.e. it’s a reaction and you have new stuff / Burning, tarnishing, rusting, etc
18. Ionic compounds that contain hydrogen in place of the positive metal ion are called _____acid_____. They have what properties? Ionic compounds that contain OH polyatomic ion in place of a non-metal are called ____base_____. They have what properties? What happens when these two types of compounds are combined? Acids give of H+ ions, are corrosive, react with metals, taste sour, feel sticky. Bases give off OH- ions, are caustic, feel slippery, taste bitter.
19. Learn the prefixes eth, meth, prop, and but. Eth= organic compounds with 1 carbon atom. Meth=organic compounds with 2 carbon atoms. Prop=organic compounds with 3 carbon atoms. But=organic compounds with 4 carbon atoms.
20. What is the difference between abiotic and biotic? Abiotic factors are environmental factors that are non-living. Biotic factors are environmental factors that are living. Give examples of both. Abiotic=rocks, air, water, salt, etc.
21. Cells are mostly made of ___water__. Cell function is measured by the production of ______protein_____.
22. Give the hierarchy of biological study starting at cell and ending at universe. Cell to individual to population to community to ecosystem to biome to planet to solar system to universe.
23. What are analogous structures? Structures that perform the same function but evolved differently for example gills and lungs.
24. What are the most common elements in living things? Carbon, hydrogen, oxygen, nitrogen.
25. What are the seven characteristics that define “being alive”? 1. Composed of cells. 2. Levels of organization. 3. Use energy. 4. Respond to the environment. 5. Grow and develop. 6. Reproduce. 7. Species adapts/changes over time.
26. The four macromolecules of life are: Proteins, lipids, carbohydrates, nucleic acids.
27. Describe the function and structure of each of the four macromolecules of life.
Carbohydrates are the sugars/energy source of life.
Proteins: the major chemical of cell growth and function. Used for enzymes, muscle growth.
Lipids: fats and hormones.
Nucleic Acid: forms DNA and RNA, used for genetic code and protein code.
28. Define the prefix hyper, hypo, and iso. Hyper= above, more. Hypo= below, less, under. Iso= the same, equal.
29. What is the law of 10%? 10 percent of the energy from the sun is absorbed by plants, 10 percent of the energy available in plants is absorbed by plant eaters, 10 percent of the energy available in plant eaters is absorbed by meat eaters.
30. Describe a food chain and food web. Food chain= direct link between plant, plant eater, meat eater (predator prey relationship). Food web=links between plants, plant eaters, and meat eaters in a community (many predator prey relationships and connections).
31. What chemicals are associated with the Greenhouse Effect? Carbon dioxide and other emissions from the burning of fossil fuels build up in the atmosphere and trap heat in the area where things live, raising the overall temperature of the surface of the earth.
32. Compare inherited traits versus acquired traits. Inherited traits are genetic traits that are coded for in DNA and can be passed on to offspring for example: eye color, hair color, etc. Acquired traits are traits that are developed during a lifespan but cannot be passed on to offspring for example working out to build muscle, changing hair color with hair dye, etc.
33. KNOW punnet squares.
Example:
34. Define homozygous, heterozygous, phenotype, and genotype. Homozygous= having two identical genes for example GG or gg. Heterozygous= having two different copies of a gene for example Gg. Phenotype= what the gene looks like, what is expressed in the organism, what you can see, for example blue eyes or brown eyes Genotype=the actual genetic combination for example Bb or BB or bb for eye color.
35. How do genetic mutations lead to changes in a species? Genetic mutations can be either helpful for survival or decrease the chances of survival. Organisms with genetic mutations that are helpful for survival are more likely to reproduce and pass on the helpful trait so the species as a whole is more likely to have that trait in the future. Genetic mutations that decrease the chances for survival cause an individual to be less likely to reproduce and that trait will slowly “die out” as it is not passed on to offspring. Are genetic mutations good or bad? Genetic mutations are neither good nor bad. Certain genetic mutations may increase an individual’s chances of survival for the current environment; however environmental change could easily make that trait decrease the chances of survival.
36. What is genetic isolation? Sexually reproducing organisms require two genetic parents. When two genetic parents are unavailable the individual is said to be “genetically isolated.” This is the risk of evolving into a sexually reproducing species. The benefits of sexual reproduction include genetic variation, adaptability through genetic mutation, and low risk of extinction due to genetically cloning traits that are unfavorable to the survival in a given environment. Asexually reproducing organisms do not risk genetic isolation. However, asexually reproducing organisms are genetic clones of the parent; therefore any trait that is not helpful to survival is always present in the offspring and can lead to mass extinction of a population.
37. LEARN YOUR VOCAB!!!!