8th Grade Science December 8, 2014 Learning Objective: Describe why the Earth has different length of day and night. Bell Ringer: Which part of an atom determines the identity of the element? Today – Day/Night

8.7 The student knows the effects resulting from cyclical movements of the Sun, Earth, and Moon (A) model and illustrate how the tilted Earth rotates on its axis, causing day and night, and revolves around the Sun causing changes in seasons.

That sounds reasonable…right? It’s complicated. Do you remember 8.5(A)? Describe the structure of atoms, including masses, electrical charges, and locations, of protons and neutrons in the nucleus and electrons in the electron cloud. Well, we still have trouble with that idea, and it is pretty straightforward.

Atomic structure (again) What part of an atom has the mass? What is the charge? What part of an atom has the most volume? What do valence electrons give you? What is the charge of neutrons?

#9 and #10 Structure of an atom #11 – Reactivity (Valence Electrons) #12 and #13 Periodic table #14 Counting atoms

8.7 The student knows the effects resulting from cyclical movements of the Sun, Earth, and Moon (A) model and illustrate how the tilted Earth rotates on its axis, causing day and night, and revolves around the Sun causing changes in seasons.

What do we need to know about 8.7(A) The Earth rotates on its axis. The axis is an imaginary line that we have discovered. All planets seem to have it. The rotation takes about 24 hours. One side of the planet will receive sunlight, while the other is dark. Day and night is the result.

Things you may not realize. Earth is tilted on its axis. 23.50 (Degrees) That tilt has changed some over time, but it is something that varies. The axis of Earth points to the “North Star” called Polaris. If you look at the stars over time, Polaris is the only one that looks like it is not moving.

Days and nights are not always equal. The tilt of the Earth causes days in the summer to be longer, and nights to be shorter. In the winter (like now) the nights are getting longer, and the days are getting shorter.

Why? Latitude. The closer you get to the equator the more sunlight you will receive. If you live at 60 degrees North, your days are very short.

Sunrise and Sunset Arlington, Texas Sunset 5:22 PM Sunrise – 7:19 AM Stillwater, Oklahoma Sunset 5:13 PM Sunrise – 7:27 AM Juneau, Alaska Sunset 3:07 PM Sunrise – 8:33 AM

Can you explain why? In your notes, explain why days are shorter in the north than the south.