grade 8 science question and answer

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Question:1. What is physical science? 2. What are 3 examples of physical science that you interact with everyday? 3. Why is lab safety important? 4. What are the 4 major areas of the metric system? 5. What is the difference between the metric system (SI Units) and the English Units of Measure? 6. Why do scientists use SI Units? 7. What items of lab equipment are used to measure mass, length, volume, and temperature? 8. What is the scientific method? 9. What are the steps of the scientific method? 10. What are the components of an experiment? 11. Why do scientists use models?

Answers:1. physical properties and laws of life. Matter and energy. 2.releasing perfume, sitting on a ball, and notices it doesn't get flat, salt dissolving in water 3.So that no one will get hurt, some chemicals will stain clothes, burn skin or even blind you 4.km, mm, m, and, L 5.metric system is used by over 95% of the world and english units are used in the united states Liberia, and Myanmar 6. So that everyone can be able to measure in the same units and tell how many units it is without having to convert it 7. mass: a scale, length: ruler, meter stick, volume: beakers, measuring cups, spoons, temperature: thermometer 8. a method of investigating and observing to test a hypothesis 9.Ask a Question Do Background Research Construct a Hypothesis Test Your Hypothesis by Doing an Experiment Analyze Your Data and Draw a Conclusion Communicate Your Results 10. question, purpose, hypothesis, materials,and procedure 11.models are bigger and easier to handle

Question:1. Which of the following scientists inferred that an atom's positive charge must be clustered in the nucleus? A) Niels Bohr B) John Dalton C) Ernest Rutherford D) J.J. Thomson 2. In an atom, the number of protons equals the number of A) Nuclei B) Electrons C) Neutrons D) Isotopes 3. Elements in Group 17 (the halogens) are the _____ reactive metals. 4. Elements that form diatomic molecules, or molecules of 2 atoms each, are commonly found on the ____ right side of the periodic table. -------------------------------- For questions 5-7, refer to http://www.corrosionsource.com/handbook/periodic/periodic_table.gif 5. List three elements from the group containing the most reactive nonmetals. 6. In each period, how does the number of electrons in each kind of atom change from left to right between Groups 1 and 2? Explain how you know. 7. How many atoms of a Group 17 elements would be needed to react with one atom of a Group 2 element? Explain. ----------------- Thanks.

Answers:1) C) Ernest Rutherford 2) B) Electrons 3) chemically (due to higher electronegativity) 4) second last goup (17th goup forms diatomic molecules) 5) halogens-Florine,Chlorine,Bromine 6)As we move from left to right atomic size decreases ,ionization energy increases and electrons are very difficult to be removed from their outer orbits 7) there are 2 atoms (1molecule) needed to react with element of group 2 example Mg + Cl2-----> 2Mgcl all the best 7)

Question:1. Which of the following is most responsible for a change from solid to a liquid? heating a substance so that its internal particles move faster and overcome the forces of attraction that hold them together increasing the pressure on a substance bringing the substance's atoms into slower motion 2. A cupful of water and a cupful of gasoline are placed in a sunny window. Both cups have the same volume of liquid in them. 24 hours later you observe that both cups have less liquid in them, but there is less gasoline than water. What can you conclude from this observation? gasoline gets hotter than water some liquids evaporate faster than others liquids evaporate only in sunshine 3. In the water cycle, water in the form of ice or snow can return to the atmosphere as water vapor. This process is called ________. condensation sublimation evaporation 4. Which of the following processes is most affected by pressure? freezing boiling melting 5. Which of the following is the best definition of sublimation? change of a liquid to a gas change of a gas to a liquid change of a solid to a gas 6. In a chemical change, the substance that changes is called the product. True False 7. A piece of metal is cut into smaller and smaller pieces until each piece is microscopically small. This is an example of a physical change. True False 8. According to Charles's Law, increasing the temperature of a balloon will have which effect on the balloon's volume? increase decrease random effect

Answers:1. A 2. B 3. B (I almost thought C but I googled it :) ) 4. B (not quite sure might want to double check) 5. C 6. T 7. T 8. A If its simple you should try to figure them out first and if you really have trouble post it here

Question:Using a screwdriver to pry off the lid to a paint can is an example of a second class lever. Question 1 answers True False Question 2 text Question 2 2 points Save A wheel is comparable to a rotating lever. Question 2 answers True False Question 3 text Question 3 2 points Save Levers have only one class. Question 3 answers True False Question 4 text Question 4 2 points Save A screw is an inclined plane wrapped around a cylindrical post that reduces the amount of force required to do work. Question 4 answers True False Question 5 text Question 5 2 points Save All simple machines are variations of two basic machines. Question 5 answers True False Question 6 text Question 6 3 points Save Which of the following describes effort force? Question 6 answers force put out by the machine force used by the machine force applied to the machine force used to change the direction of the motion Question 7 text Question 7 3 points Save What do you need to calculate the mechanical advantage of a block and tackle? Question 7 answers resistance force effort force number of rope segments that support the resistance weight number of pulleys in the block and tackle system Question 8 text Question 8 3 points Save The number of times a machine multiplies the effort force is? Question 8 answers resistance force effort distance mechanical advantage efficiency Question 9 text Question 9 3 points Save A tape dispenser is an example of which simple machine? Question 9 answers pulley lever inclined plane screw Question 10 text Question 10 3 points Save Which of the following is an example of an incline plane? Question 10 answers lever gear pulley screw Question 11 text Question 11 3 points Save A doorknob is an example of which simple machine? Question 11 answers lever pulley inclined plane wheel and axle Question 12 text Question 12 3 points Save A handicap ramp on a building is the example of which simple machine? Question 12 answers lever wheel and axle pulley inclined plane Question 13 text Question 13 3 points Save The lid on a jar is an example of which simple machine? Question 13 answers screw lever pulley wheel and axle Question 14 text Question 14 3 points Save When the length of the effort arm of a lever is decreased which of the following happens to effort force? Question 14 answers Force will decrease Force will vary Force will remain the same Force will increase Question 15 text Question 15 3 points Save When you decrease the length of the effort arm on a lever which of the following happens to effort force? Question 15 answers Force will decrease Force will increase Force will vary Force will remain the same.

Answers:1. Using a screwdriver to pry off the lid to a paint can is an example of a second class lever. Question 1 answers False - because it is the first class of lever as fulcrum is in center Question 2 text Question 2 2 points Save A wheel is comparable to a rotating lever. Question 2 answers True - as effort and load are equal and while rolling fulcrum moves forward as wheel rotates Question 3 text Question 3 2 points Save Levers have only one class. Question 3 answers False - because they have three classes: fulcrum in center effort in center and Load in center Question 4 text Question 4 2 points Save A screw is an inclined plane wrapped around a cylindrical post that reduces the amount of force required to do work. Question 4 answers True - just imagine the unwinding of the screw and see what happens to the threads; they straighten out Question 5 text Question 5 2 points Save All simple machines are variations of two basic machines. Question 5 answers True- No incline plane and lever, because pulley/wheel can be considered as rotating lever and all levers are to be counted as one LEVER Question 6 text Question 6 3 points Save Which of the following describes effort force? Question 6 answers force used by the machine force applied to the machine Question 7 text Question 7 3 points Save What do you need to calculate the mechanical advantage of a block and tackle? Question 7 answers number of pulleys in the block and tackle system Question 8 text Question 8 3 points Save The number of times a machine multiplies the effort force is? Question 8 answers mechanical advantage Question 9 text Question 9 3 points Save A tape dispenser is an example of which simple machine? Question 9 answers pulley Question 10 text Question 10 3 points Save Which of the following is an example of an incline plane? Question 10 answers screw Question 11 text Question 11 3 points Save A doorknob is an example of which simple machine? Question 11 answers wheel and axle Question 12 text Question 12 3 points Save A handicap ramp on a building is the example of which simple machine? Question 12 answers inclined plane Question 13 text Question 13 3 points Save The lid on a jar is an example of which simple machine? Question 13 answers screw Question 14 text Question 14 3 points Save When the length of the effort arm of a lever is decreased which of the following happens to effort force? Question 14 answers Effort Force will increase if by force is meant the force applied at the effort arm for a fixed load Question 15 text Question 15 3 points Save When you decrease the length of the effort arm on a lever which of the following happens to effort force? Same answer as 14 because question is no different.