Will give the brainlest

answer questions #1-3 based on the following scenario.
scientists tested the effect of a fertilizer on the growth of plants. they had 2 sets of plants, group a which gets fertilizer, water and sun and group b which gets only water and sun (but in equal amounts to group a).
1 . explain how this scenario is a controlled experiment and identify the manipulated variable.

2. if the scientists only performed 1 experiment but it supported their hypothesis, why can it not be considered a theory?

4. you make the following measurements of an object: 42 kg and 22 m3. what would the object’s density be? show your work for credit and include final units.

5. explain why a chlorinated swimming pool water would be a homogenous mixture?

6. both slicing a tomato and a chemical change such as burning toast cannot be reversed. however, why is slicing a tomato still considered only a physical change?

7. if an ice cube melts at 0oc but water also freezes at 0oc, what is the difference between melting and freezing in terms of (a) the energy involved in the phase changes and (b) particles of the substances during the phase changes?

10. if measurements of a gas are 75l and 300 kilopascals and then the gas is measured a second time and found to be 50l, describe what had to happen to the pressure (if temperature remained constant). include which law supports this observation.

11. which statement matches the scientists to their research on atomic theory?
a. dalton used gold foil; bohr made the planetary model of atoms
b. thomson used gold foil; dalton believed atoms had no internal structure
c. rutherford used gold foil; thomson discovered electrons
d. rutherford discovered electrons; thomson made the planetary model of atoms

for questions #14 – 17, write an equation for the reaction of magnesium chloride and sodium oxide to produce magnesium oxide with sodium chloride.
14. show the formulas of the reactants.

15. show the formulas of the products.

16. write the balanced the equation for this reaction.

17. what type of chemical reaction is this? how do you know?

18. when is an atom unlikely to react and form chemical bonds?

19. what is the order of the types of nuclear radiation from lowest to highest energy?

20. which statement is false? rewrite it so that it is true.
a. fusion involves the combination of two smaller atoms into a larger atom.
b. fission involves the splitting of an atom into smaller atoms.
c. fission and fusion are two processes that release very little amounts of energy.
21. what naturally occurring radioisotope is used as the fuel for a nuclear reactor?

22. magnesium oxide is a binary ionic compound. from its formula, mgo, how do you know that mg is the metal?

23. on the periodic table, there are two numbers in the block for the element potassium, k: 19 and 39.098. what are the names of the numbers and what do they measure?
24. element x has five valence electrons, element y has one valence electron, and element z has one valence electron. which two of these elements are most likely to have similar properties? explain your answer.

fill in the blank: type your answer in the blank, or in the space below the question. use only the textbook to create your solutions. do not use the internet.
25. from left to right across a period in the periodic table, elements become less and more in their properties.
26. francium has 36 isotopes, but only francium-223 occurs in nature. francium-223 spontaneously emits particles and energy, so francium-223 is a(an) of francium.
27. at sea level, water at 100°c.
28. cooking requires continuous addition of energy to the chemical reactions that are taking place. the chemical reactions involved in cooking can be described as
29. the theory of matter states that all particles of matter are in constant motion.
30. in rutherford’s experiments, some of the aimed at gold atoms bounced back, suggesting that a solid mass was at the center of the atom.
31. you are given the melting points of three unknown substances and are asked to predict which one is an ionic compound. you would select the compound with the melting point.
32. a flight simulator that astronauts prepare for a shuttle launch is an example of a(an)
33. in the symbol ■([email  protected]) he, the superscript 4 is the for helium, and the subscript 2 is the for helium.