Unit 6 test review

Why is water called a "polar molecule"?

• It comes from the North Pole

• It has slightly charged ends

• It's always cold

• It's magnetic

Answer explanation

Water is called a "polar molecule" because it has slightly charged ends, with one end being more positive and the other more negative. This polarity allows water to form hydrogen bonds, which are crucial for its unique properties.

Tags

NGSS.HS-PS2-6

What does "universal solvent" mean?

• It can dissolve anything

• It's found everywhere

• It can dissolve many substances

• It's used in space

Answer explanation

The term "universal solvent" refers to a substance, primarily water, that can dissolve many different substances, making it essential in various chemical processes. It does not mean it can dissolve everything or is found everywhere.

Tags

NGSS.MS-ESS2-4

What is cohesion?

• Water sticking to other substances

• Water molecules sticking to each other

• Water evaporating

• Water freezing

Answer explanation

Cohesion refers to the attraction between water molecules, causing them to stick together. This property is crucial for various phenomena, such as surface tension, making 'Water molecules sticking to each other' the correct choice.

Which is NOT a state of matter for water on Earth?

• Solid

• Liquid

• Gas

• Plasma

Answer explanation

Plasma is not a state of matter for water on Earth. Water exists in three states: solid (ice), liquid (water), and gas (water vapor). Plasma, while a state of matter, does not occur naturally for water under normal Earth conditions.

Tags

NGSS.MS-PS1-4

Why does water expand when it freezes?

• It becomes denser

• Its molecules spread out

• It absorbs air

• It changes color

Answer explanation

Water expands when it freezes because its molecules spread out to form a crystalline structure, making ice less dense than liquid water. This unique property is why ice floats.

Tags

NGSS.MS-PS1-4

Which phase of water is the most dense?

• Ice

• Liquid water

• Water vapor

• They're all equally dense

Answer explanation

Liquid water is the most dense phase of water. Ice is less dense due to its crystalline structure, and water vapor is the least dense as it consists of gas molecules spread apart. Thus, liquid water has the highest density.

What is capillary action?

• Water moving down a plant

• Water moving up a plant stem

• Water evaporating from leaves

• Water freezing in plants

Answer explanation

Capillary action is the process where water moves up a plant stem against gravity, due to the adhesive forces between water molecules and the plant's xylem. This is essential for transporting water and nutrients.

Tags

NGSS.MS-LS2-3

What is transpiration?

• Water moving up a plant stem

• Water evaporating from leaves

• Water being absorbed by roots

• Water freezing in plants

Answer explanation

Transpiration is the process where water evaporates from the leaves of a plant. This process helps in nutrient transport and temperature regulation, making 'Water evaporating from leaves' the correct answer.

In a water molecule which part has a slight positive charge?

• Oxygen

• Hydrogen

• Carbon

• Nitrogen

Answer explanation

In a water molecule (H2O), the oxygen atom is more electronegative than hydrogen atoms, causing the hydrogen atoms to have a slight positive charge. Therefore, the correct answer is hydrogen.

What happens during physical weathering?

• Rocks change chemically

• Rocks break into smaller pieces

• Rocks dissolve completely

• Rocks become magnetic

Answer explanation

During physical weathering, rocks break into smaller pieces without changing their chemical composition. This process can occur due to factors like temperature changes, freeze-thaw cycles, or abrasion.