Biological Significance of Water

Water is essential for life. Its special properties make water the single most important molecule in plant life. Which of the following properties of water enables it to move from the roots to the leaves of plants?

• Water expands as it freezes.
• Water is an excellent solvent.
• Water exhibits cohesive behavior.
• Water is able to moderate temperature.

Large bodies of water, such as lakes and oceans, do not quickly fluctuate in temperature. What is the reason for this phenomenon?

• Water is an acid.
• Water is a versatile solvent.
• Water has a high heat capacity.
•  Water acts as a buffer.

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NGSS.MS-PS1-4

NGSS.MS-PS3-4

Why does ice stay at the top of oceans instead of sinking to the bottom?

•  Ice is colder than liquid water.
• Ice is less dense than liquid water.
• Ice is more dense than liquid water.
• Ice is warmer than liquid water.

Water is often called the "universal solvent" because many substances can be dissolved in water. What property of water allows it to be such a versatile solvent? 

• purity
• polarity and cohesion
• high heat capacity
• expansion upon freezing

 Small insects can walk across the surface of calm water. Their feet push the surface of the water down slightly, somewhat like a person walking across a trampoline, but they do not break the surface. What is the best explanation for why this happens?

• The insects are light enough so that they do not break the hydrogen bonds holding the water molecules together
• The insects actually use their wings to hover slightly above the water's surface and they only skim it with their feet
• The insects' feet are non-polar, so they are repelled by the polar water molecules and are pushed away from the water's surface
• The insects are small enough to see the individual water molecules, so they are able to step carefully from one molecule to the next

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NGSS.MS-PS2-5

A florist places a bouquet of white carnations in water containing blue dye. After a time, the flowers turn blue. What process helped the carnations to change color?

• Specific heat 
• Surface tension
• Cohesion and adhesion of water molecules 
• Formation of covalent bonds between hydrogen and oxygen molecules

Water makes up approximately 60% of the human body and plays a vital role in regulating body temperature. Which property of water makes it good at regulating temperature?

• Water is a good solvent.
• Water exhibits strong cohesion.
• . Water has an unusual crystalline structure.
• Water has a high capacity for heat.

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NGSS.HS-ESS2-5

Water has a much higher specific heat than most other covalent compounds. What do you predict might happen if water had a low specific heat instead?

• Flooding would occur and animals would be forced to migrate
•  Harmful organisms living in water would reproduce at a rapid rate
• Organisms that are sensitive to changes in temperature would die
• Plants would not have enough water to effectively carry out photosynthesis

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NGSS.MS-LS1-5

 Many fish and aquatic plants can survive a cold winter because the layer of ice that forms at the top of the lake insulates the water below and prevents the lake from freezing solid. What unique property of water contributes to this effect? 

• Water absorbs heat when it evaporates and forms a gas 
•  Water expands and becomes less dense when it freezes.
• Water molecules completely separate into ions in solutions.
•  Water forms hydrogen bonds with ions and other polar substances. 

Tags

NGSS.HS-ESS2-5

 Which of the following characteristics of water is not a result of hydrogen bonding?

• adhesive strength
• capillarity
• cohesive strength
• All of the above are a result of hydrogen bonding.