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# Tutor profile: Jennifer D.

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Jennifer D.
Teacher and Tutor for 8 years
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## Questions

### Subject:Chemistry

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Question:

What are isotopes? In what ways are they similar? In what ways do they differ?

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Jennifer D.

Isotopes are the same element with different mass numbers. C-14 and C-13 are isotopes of each other. They are both the element Carbon, however they have different mass numbers; 14 and 13. Both of these samples have 6 protons. All elements of the same element MUST contain the same number of protons, as identified by the atomic number of the element, represented on the Periodic Table of Elements. Since these samples are not ions (charged), they must also have the same number of electrons. In an atom (an uncharged sample) the number of protons and electrons must be equal. Since the mass numbers of these two samples are different, this means that the number of neutrons must be different. Mass number of a sample is determined by adding together the number of protons and neutrons. Let's look at these two samples. We have already decided that the number of protons in C-14 and C-13 must be equal. They both have 6 protons because the atomic number of Carbon is 6. Carbon-14, therefore, has 8 neurons. How did I get this? We already decided that the mass number is equal to the number of protons plus the number of neutrons. We know the mass number because it is given in the sample's name. Carbon-14 indicates that we have a sample of Carbon with a mass number of 14. Therefore, 14-6=8. (14 being the mass # - 6, which is the number of protons = 8 which is the number of neutrons. Now let's do the same thing with C-13. Carbon-13 must have a mass number of 13. Carbon-13 has 6 protons because again it has an atomic # of 6. Let's do the same math as before. 13-6 = 7. Therefore the sample of carbon-13 has 7 neutrons. Recap: Isotopes have the same: 1. # of protons (they are samples of the same element and have the same atomic # which means they have the same amount of protons. 2. # of electrons (since they are atoms and not ions, they must have the same number of protons and electrons.) Isotopes have different: 1. Mass numbers and therefore different number of neutrons. (mass number = # of protons + # of neutrons)

### Subject:Biology

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Question:

Vaccines are a subject of great debate amongst parents and doctors. What exactly are vaccines? How do vaccines help us, not only as individuals, but also as a population?

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Jennifer D.

### Subject:Physics

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Question:

What is the basic method used to solve a parabolic trajectory question?

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Jennifer D.

There are several steps to this process. The first step is that you must split up the motion of the trajectory into an x (horizontal) motion and a y (vertical motion). Think about when you "lob" a ball to your friend. The ball has both height (y) and distance (x). From here you would create a chart to show acceleration, initial velocity, final velocity, and distances in both the x and y directions. Once you have completed your chart, you can refer to your kinetics equations and decide which formula you use to determine the missing variables (this will differ depending on the variables given in the problem to be solved).

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