Tutor profile: Jen B.
Subject: Earth Science
What are the steps of the water cycle?
Water on Earth is continually cycling around us. Water on the oceans surface can evaporate, or change phase from a liquid to a gas, when the molecules become excited. When in the gas phase, they rise up into the sky because they are less dense. As they rise, the air becomes cooler, which increases the density and causes the molecules to condense or change phase from a gas to a liquid (water droplets). When too many of these come together, their combined weight is too much to stay aloft in clouds and they fall to the surface of the Earth in the form of precipitation (rain, snow, sleet, hail, etc). Some of this water then becomes runoff along the surface and flows back to the oceans. Some of it may also infiltrate the Earth's surface and become groundwater which will either be absorbed by plants and transpired back into the atmosphere, or will eventually flow back to the oceans (although this may take a long time). Once in the ocean, the cycle repeats itself again and again.
Subject: Basic Chemistry
How can you identify the number of neutrons in an element?
When you look at the periodic table, there are two numbers that should stand out for each element. The first number (usually on top) is called the atomic number and tells you the number of protons in the nucleus of a single atom of that element. The bottom number is known as the mass number, and sometimes has a decimal value. This bottom number indicates the average mass of one atom of that element. Now, most of the mass of an atom comes from protons and neutrons as electrons barely have any mass at all. So, if you were to take the mass number (bottom) and subtract the atomic number (top), it will give you the number of neutrons in that atom. If there is a decimal point, it is because not every atom of a given element always has the same number of neutrons. This is due to isotopes which we will talk about in another lesson.
Subject: Physical Science
How can you explain the concept of density to me in a more understandable way?
Density is defined as how much matter ("stuff") will fit in a given volume (space). Imagine that you get in an elevator and you are the only person there. You (the "stuff") have a decent amount of space to move around. As more people get in the elevator with you, you increase the amount of "stuff", but keep the same amount of space or volume. Therefore, the density has increased. As soon as the door opens, though, the people in the elevator (the "stuff") are now allowed to spread out and fill a larger room with more space (or volume). Now, each person is free to move around more, and the overall density has decreased.
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