accurate description of a theory, chemistry homework help

QUESTION 1Which of the following is an accurate description of a theory?a well-tested explanation for how something works.an observation made over and over again.someone’s idea about how something works.easily proved wrong and therefore cannot be trusted in science.3 points Save AnswerQUESTION 2Which of following statements is true about scientific knowledge?Scientific ideas are not subject to change, and so knowledge stays the same.Scientific knowledge is constantly evolving as new observations are made.While scientific knowledge increases over time, old knowledge never changes.Theories can change frequently, but scientific knowledge is absolute.3 points Save AnswerQUESTION 3Which of the following is an example of pure research?Determining the causes of dementia in elderly people.Creating robots to walk on the surface of Mars.Colliding subatomic particles at high speeds to see what they form.Working with alloys to determine the lightest carbon fiber composition for armor.3 points Save AnswerQUESTION 4Which of the following institutions employs scientists?HospitalsUniversitiesCorporationsAll of the above3 points Save AnswerQUESTION 5If the flame of a Bunsen burner should accidentally go out, a student should immediately run over to the teacher and inform him/her.TRUEFALSE2 points Save AnswerQUESTION 6In terms of eye safety in the lab:Students do not need to wear safety goggles if they already have prescription glasses on.Students need to wear safety goggles at all times, regardless if they have prescription glasses or not.Students only need to wear safety goggles if they do not have their own prescription glasses or if they have contacts.Goggles only need to be worn if the chemicals used in a lab are liquids or solutions.3 points Save AnswerQUESTION 7You observe that a liquid has decreased volume by 23.4 milliliters (mL) during the duration of an experiment. What is this type of observation?quantitativequalitativeindirect observationa physical change3 points Save AnswerQUESTION 8It is equally accurate to measure volumes with a beaker as with a graduated cylinder.TRUEFALSE2 points Save AnswerQUESTION 9When measuring the volume of a liquid in a graduated cylinder, you should raise the cylinder up to eye level to read the meniscus more accurately.TRUEFALSE2 points Save AnswerQUESTION 10To accurately measure the volume of a typical liquid in a graduated cylinder, what should you do?look at the bottom part of the meniscuslook at the top part of the meniscusaverage the top and bottom parts of the meniscusignore the meniscus and determine which mL line the liquid is closest to3 points Save AnswerQUESTION 11To accurately measure out 35 milliliters of liquid, you should use:a 10-mL glass pipette several timesa 50-mL beakera 25-mL graduated cylinder two timesa 50-mL graduated cylinder one time3 points Save AnswerQUESTION 12Two groups complete an experiment requiring the mass measurement to be repeated three times in the experiment. Group I selects a single member of the group to measure the mass. Group II allows any person of the group to measure the mass once, so they will be done more quickly. At the end of the experiment, the results for group I are closer to the actual than the results of group II. Explain why this might be.Press Tab to enter the content editor. For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac).Path: pWords:05 points Save AnswerQUESTION 13Which of the following would be considered the most heterogeneous mixture?oil/vinegar salad dressingpasteurized milkvinegarolive oil3 points Save AnswerQUESTION 14Which of the following pairs forms a homogenous mixture after being mixed together?sand and watersalt and wateroil and wateroil and vinegar3 points Save AnswerQUESTION 15Which of the following is an example of a physical change?Rusting bicycle chainMelting butterFireworks explodingBaking a cake3 points Save AnswerQUESTION 16Which of the following is an example of a physical change?Separating sand from gravelBaking a pieBurning a piece of paperRusting3 points Save AnswerQUESTION 17Of the following examples, select those that represent a chemical change.I. Water freezing and changing into iceII. Leaves changing color in the fallIII. Mixing lemonade mix powder with waterIV. Milk going sourII, III, IVI, II, III, IVII, IVI, II3 points Save AnswerQUESTION 18Which of the following is an example of a chemical property?FlammabilityBoiling pointDensityElasticity3 points Save AnswerQUESTION 19A mixture of sand and iron filings can be separated into its individual components by using a magnet.TRUEFALSE2 points Save AnswerQUESTION 20Which of the following is NOT a method used to physically separate components in a mixture?chromatographysublimationdistillationprecipitation3 points Save AnswerQUESTION 21The best way to separate ethanol from its solution in water is to use which of the following?chromatographyprecipitationdistillationfiltration3 points Save AnswerQUESTION 22The standard (Bohr) model of the atom shows that:a positively charged nucleus has negatively charged particles surrounding ita neutrally charged nucleus has neutrally charge particles encompassing ita negatively charged nucleus has positively charged particles encompassing ita positively charged nucleus has positive or negatively charged particles encompassing it3 points Save AnswerQUESTION 23An atom has no electrical charge because:its subatomic particles have no electrical chargesthe positively charged neutrons cancel out the negatively charged electronsthe negatively charged neutrons cancel out the positively charged protonsthere are as many positively charged protons as negatively charged electrons3 points Save AnswerQUESTION 24The atomic number represents the total number of protons and neutrons in an atom.TRUEFALSE2 points Save AnswerQUESTION 25Electrons exist only outside of the nucleus.TRUEFALSE2 points Save AnswerQUESTION 26Pick the correct statement for the following isotope: 42Ca42 is the mass number and 20 is the atomic number.42 is the number of neutrons and 20 is the number of protons.42 is the number of protons and 20 is the number of electrons.42 is the atomic number and 20 is the number of neutrons.3 points Save AnswerQUESTION 27In structure, the standard (Bohr) model of the atom is most similar toplum puddingour solar systemchocolate chip cookie doughthe Milky Way galaxy3 points Save AnswerQUESTION 28Most of the volume of an atom is contained:in the protonsin the nucleusin the neutronsin the empty space around the nucleus3 points Save AnswerQUESTION 29In comparing two isotopes of the same element, the atomic number:changes to reflect the number of protons.changes to reflect the new mass number.changes to reflect the number of new neutrons.stays the same.3 points Save AnswerQUESTION 30If the number of protons for an element changes, then:the element turns into an isotopethe element becomes a different elementthe number of electrons for that element changes as wellthe number of neutrons changes as well3 points Save AnswerQUESTION 31Use the information for the isotopes of element X to calculate the average atomic mass of X, and identify the element.Isotope Abundance Mass (amu)35X 75.77% 34.96937X 24.23% 36.965Press Tab to enter the content editor. For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac).Path: pWords:05 points Save AnswerQUESTION 32Which of the following statements about subatomic particles best characterizes protons?positive charge, heavy, found in the nucleus of an atomno charge, heavy, found in the nucleus of an atomnegative charge, light, circling the nucleus of an atomno charge, light, circling the nucleus of an atom3 points Save AnswerQUESTION 33Henry Moseley determined that, with a few exceptions, the order of increasing atomic number is the same as increasing atomic mass.TRUEFALSE2 points Save AnswerQUESTION 34Who was the first person to organize the elements so that properties of undiscovered elements could be predicted?J.W. DobereinerDmitri MendeleevJJ ThomsonErnest Rutherford3 points Save AnswerQUESTION 35Generally, when going from left to right across a period on the periodic table:atomic radii decreaseionic radii increaseelectronegativity decreasesvalence electron number decreases3 points Save AnswerQUESTION 36In the periodic table, alkali metals are situated:At the extreme left side.At the extreme right side.Towards the middle of the periodic table.Directly next to the right of the stair steps/metalloids.3 points Save AnswerQUESTION 37Generally, when going down columns 1 or 2 of the periodic table, the reactivity of elements:increasesdecreasesremains the same except for noble gasesremains the same except for halogens3 points Save AnswerQUESTION 38Which of the following classifications is NOT correct?Group 1 and Group 2 – MetalsGroup 7 – HalogensGroup 8 – Noble GasesGroup 5 – Metalloids3 points Save AnswerQUESTION 39Which of the following classifications is NOT correct?Noble gases – 8 valence electronsHalogens – 6 valence electronsTransition metals – number of valence electrons variesAlkali Rare Earth metals – 2 valence electrons3 points Save AnswerQUESTION 40The chemical symbol for lead is La.TRUEFALSE

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