Science End of Year Review

Lithium is a metal with an oxidation number of 1⁺ and oxygen is a nonmetal with an oxidation number of 2^-. Which chemical formula represents the compound formed by these two elements?

• Li2O

• Li₃O

• LiO

• LiO2

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The underwear in the image keeps you warm on cold nights because it

• prevents radiation

• is a poor insulator

• prevents conduction

• it's a good conductor

The compound formed has a(n) ___________ bond and is a(n) _________________.

• ionic; crystalline solid

• covalent; amorphous solid

• metallic; crystalline solid

• covalent; crystalline solid

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NGSS.MS-PS1-1

The decomposition of dinitrogen tetraoxide into nitrogen gas and oxygen gas is shown by which balanced chemical equation?

• N2(g) + 2O2(g) → N2O4(g)

• N2O4(g) → N2(g) + O2(g)

• N2O4(g) → N2(g) + 2O2(g)

• N2O4(g) + 2O2(g) → N2(g)

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Two isotopes of hydrogen fuse to form a neutron plus the larger element,

• beryllium

• carbon

• deuterium

• helium

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A wedge, which is used to split objects, distributes the force applied on its blunt face as shown in the image.

The distribution of force occurs because

• a wedge has three flat faces.

• the sides of the wedge are inclined.

• most of the force is absorbed by the blunt face.

• the applied force is felt only at the sharp edge.

Which statement is true?

• Batteries supply alternating current.

• Electromagnetic induction supples direct current.

• In the US, the main source of electricity is from direct current.

• In the US, the supply of AC mainly relies upon our natural resources.

What is the advantage of the system of gears shown in the image?

• The larger gear can be moved by applying a relatively small force on the smaller gear.

• The force applied on the smaller gear is transmitted without any loss to the larger gear.

• The direction of motion can be changed without changing the direction of the applied force.

• The system would continue to move without any further force, after an initial force has set it in motion.

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NGSS.MS-ETS1-1

A man has an air conditioner he wants to load into the back of his truck. Instead of lifting the air conditioner and carrying it to the truck, he improvises a ramp. He takes a board that is 3.6 meters long and places one end of it in the back of his truck, 1.2 meters off the ground. He leaves the other end of the board on the ground. He places the air conditioner on a dolly and pushes them both up the ramp and into the truck. What is the mechanical advantage of the ramp?

• 2.5

• 3.0

• 4.32

• 4.8

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The oxidation number of all metals on the periodic table have a positive (+) charge. Which of these BEST explains why?

• Metals are known to add protons to their nuclei causing them to become positively charged.

• All metals lose one or more valence electrons to become stable, giving them a positive oxidation number.

• All metals gain one or more valence electrons to become stable, giving them a positive oxidation number.

• Metals are known to lose protons and add neutrons to their nuclei causing them to become positively charged.

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NGSS.MS-PS1-1

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