Answer:
His mistake was that he also gave the plants in the music room some fertilizer
Explanation:
When carrying out a reliable experiment, the only variable should be the question being tested. The question here is whether playing music for plants helps them grow faster. Therefore, all the plants should be grown in exactly the same conditions apart from the presence or absence of music.
However, Jo also added fertilizer to the plants in the room where music was playing. Therefore, we don't know whether the fertilizer or the music caused the plants to grow faster.
Instead, Jo should have not given fertilizer to any of the plants, or given fertilizer to all the plants.
Answer:
An experiment is an investigation in which a hypothesis is scientifically tested. In an experiment, an independent variable (the cause) is manipulated and the dependent variable (the effect) is measured; any extraneous variables are controlled. An advantage is that experiments should be objective.
Explanation:
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1. C
2. A
3. A & B
4. C
5. C
6. A
7. A
8. A & C
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Answer:
1. the group number of sodium is 1 and it is a metal
2. the group number of helium is 18 and it is a nonmetal
3. the group number of iodine is 17 and it is a nonmetal
4.the group number of calcium is 2 and it is a metal
5. lithium has similar properties to potassium
6. calcium has similar properties to magnesium
7. neon has similar properties to xenon
8. Iodine has similar properties to chlorine
Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
