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# Tutor profile: Mackenzie M.

Inactive
Mackenzie M.
Experienced Tutor, Biology/Ecology Major in University
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## Questions

### Subject:Spanish

TutorMe
Question:

En vez de preguntar algo y responder, yo quiero explicarte como aprendí el español.

Inactive
Mackenzie M.

Cuando yo tenía once años, mi familia y yo viajamos a Costa Rica. En vez de aprender las matemáticas y la historia para dos meses, asistimos las clases de español. Después de volvimos a los EEUU, yo practicaba el español in las clases del colegio. Al fin de mi colegio, viajé a Peru para pasar un mes enseñando los estudiantes discapacitados. Finalmente, durante la universidad pasé tres meses trabajando en Chile. Tengo mucho para aprender de la idioma, y mi español no es perfecto! Pero, hablo bastante mucho para ayudarles con las clases del colegio y la universidad.

### Subject:Basic Chemistry

TutorMe
Question:

Where do electrons live in an atom?

Inactive
Mackenzie M.

This question depends a lot on your level of chemistry! As I was learning chemistry, it seemed like every time I moved into the next level, the class started with, "so, you're about to find out that we lied to you last year..." That's okay! Here's the level that you'll want to know in an advanced high school class. Electrons live within an atom's valence orbitals. The number of orbitals that an atom has, depends on its atomic number and therefore (indirectly) the number of electrons it has. There are s, p, d, and f orbitals. Within each orbital there are valence shells. S orbitals have 1 valence shell, p orbitals have 3 shells, d orbitals have 5 shells, and f orbitals have 7 shells. Then, each valence shell can hold two electrons. This means that s orbitals hold 2 electrons, p orbitals hold 6 electrons, d orbitals hold 10 electrons, and f orbitals hold 14 electrons. I like to think of an atom has a house with many rooms. S orbitals are one bedroom houses, p orbitals are three bedroom houses, d orbitals have five bedrooms, and f orbitals have seven orbitals. Each bedroom has a double bed and can sleep two people. The people are like the electrons, the rooms are like the orbitals, and the house is like the entire atom.

### Subject:Biology

TutorMe
Question:

Why is it that a tree might die if you cut its bark deeply?

Inactive
Mackenzie M.

This is a bit of a complicated question that has to do with the way that trees transport water and nutrients through their xylem and phloem. Water evaporates out of little pores in the leaves of a tree called stomata. This evaporation creates a lower pressure in the leaves than in the rest of the tree, so water travels upwards through the xylem to increase the water pressure in the leaves. Nutrients are dissolved in phloem sap that travels through another type of tubular structure in the tree called phloem. Water enters the phloem from the xylem at the base of the tree. Once the phloem reaches the leaves, where the nutrients are needed, the water goes back into the xylem and can evaporate out of the stomata. When you cut a trees bark deeply, it can slice through the phloem. This causes an area of negative pressure near the cut, and so phloem will flow to the cut instead of to the leaves. Since the phloem sap is leaving the tree, more water will enter the phloem from the xylem. This means that the tree's leaves are no longer getting the water or nutrients it needs, the tree will die.

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