Water and Intermolecular Forces

What two elements make up water?

• Helium and oxygen
• Hydrogen and oxygen
• helium and carbon
• oxygen and carbon

Tags

NGSS.MS-PS1-1

What word describes when water is attracted to other substances?

• cohesion

• adhesion

• capillary action

• surface tension

Answer explanation

The term 'adhesion' describes when water is attracted to other substances. It is the property of water that allows it to stick to non-water molecules. This differentiates it from 'cohesion', which refers to water sticking to itself. 'Surface tension' and 'capillary action' are also water properties, but they don't specifically describe water's attraction to other substances.

Attractions between the partially negative Oxygen atom of one water molecule and the partially positive Hydrogen atom of another water molecule are called

• Covalent bonds
• Ionic bonds
• Polar bonds
• Hydrogen bonds

Why does ice float?

• As water freezes, it expands and its density decreases.

• As water freezes, it takes up more hydrogen from the atmosphere, causing it to have a greater buoyancy.

• As water freezes, air becomes trapped between the hydrogen bonds of water molecules.

• As water freezes, it takes up more oxygen from the atmosphere, causing it to have a greater buoyancy.

Answer explanation

The reason why ice floats in water is due to the property of water when it freezes. As water freezes, it expands and consequently, its density decreases. This makes ice less dense than the surrounding water, causing it to float.

Water is a universal solvent because it...

• It can be found anywhere

• It freezes when it gets cold

• floats when frozen

• Dissolves most substances

Answer explanation

Water is often referred as a 'universal solvent' because of its ability to dissolve most substances. This is due to the polar nature of water molecules. The answer choice 'Dissolves most substances' accurately captures this characteristic of water.

Which of the following is LEAST likely to dissolve in water?

• nonpolar fats and oils

• polar sugar molecules

• salt made of a positive sodium ion and a negative chloride ion

• all of the substances will dissolve easily in water

Answer explanation

Nonpolar fats and oils are the least likely to dissolve in water. This is because water is a polar substance and 'like dissolves like'. Polar substances will dissolve other polar substances and nonpolar substances will dissolve in other nonpolar substances. Therefore, nonpolar fats and oils do not dissolve readily in water.

 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

Answer explanation

Surface tension results from the cohesive forces between water molecules. When an object is light enough, like an insect, it doesn't have enough force to break these bonds and thus can walk on water. Thus, the correct answer is that insects are light enough so they don't break the hydrogen bonds holding water molecules together.

Tags

NGSS.MS-PS2-5

Water is a compound that consist of 3 atom which is 2 atom oxygen and 1 atom hydrogen

• True

• False

Tags

NGSS.MS-PS1-1

What term describes the attraction between water molecules?

• Adhesion

• Cohesion

• Capillary action

• Surface tension

What type of bond is formed between two water molecules?

• Ionic bond

• Covalent bond

• Metallic bond

• Hydrogen bond