Unit 2 (Chemistry) Chapter 2 (Properties of Water)

Question 1

4 Characteristics of Water

Answer 1

1. Water is cohesive
2. Water moderates temperature
3. Solid water is less dense than liquid water
4. Water is the solvent of life

Question 2

Cohesion

Answer 2

Tendency of the same kind of molecules to stick together.
- Stronger for H2O than other liquids

Question 3

Adhesion

Answer 3

Clinging of one substance to another

Question 4

Surface Tension

Answer 4

Measure of how hard it is to stretch or break the surface of a liquid

Question 5

Thermal Energy

Answer 5

Energy associated with random movement of atoms & molecules

Question 6

Temperature

Answer 6

Measure of the intensity of heat. The average speed of molecules in a body of matter
- Water heats up slower than other compounds like metals

Question 7

Evaporation

Answer 7

Change of a substance from liquid to gas state

Question 8

Evaporative Cooling

Answer 8

When evaporation occurs, the liquid that remained becomes cooler than before

Question 9

Examples of Temperature Moderation

Answer 9

• Warm molecules move faster than cold
• Hydrogen bonds need to be broken to allow molecules to move faster

Question 10

Benefits of Water on Earth

Answer 10

1. Regulates temperature of planet to allow for life
2. In warm periods, water stores heat from sun
3. In cold periods, water releases stored heat & warms up air
4. Water moderates body temp
   - Body is 66% water

Question 11

What happens when hot molecules evaporate?

Answer 11

It’s average temperature lowers compared to before

Question 12

What happens to hydrogen bonds when water freezes?

Answer 12

They are stabilized at a specific bond length
- Creates 3D crystal

Question 13

What happens to lake or ocean water as it freezes?

Answer 13

The ice floating insulates the liquid water underneath allowing for organisms to live

Question 14

What is a solution?

Answer 14

Liquid that contains a uniform mixture of two or more substances

Question 15

Solvent

Answer 15

Dissolving agent

Question 16

Solute

Answer 16

Substance that’s dissolved

Question 17

Aqueous Solution

Answer 17

A solution that has water as a solvent

Question 18

Can Water Dissolve Ionic Compounds? If so, what’s an example?

Answer 18

Yes, water can dissolve any ionic compound
- Ex. NaCl dissolved in H2O
(Positive H atoms are attracted to Cl- ions ; Negative O atoms are attracted to Na+ ions)

Question 19

Can Water Dissolve Non-ionic Compounds? If so, what’s an example?

Answer 19

Yes, it can.
- Ex. Spoonful of sugar will dissolve in water (water will surround compound and form hydrogen bonds with polar regions on their surfaces).

Question 20

Acid

Answer 20

Substance that donates H+ to a solution
- Has a higher concentration of H+ than OH-

Question 21

Base

Answer 21

Substance that reduces amount of H+ in a solution

Question 22

pH Scale

Answer 22

It measures how acidic an object is
- Ranges from 0 to 14
- The lower the number, the more acidic it is.

Question 23

How The pH Scale Works

Answer 23

Each pH unit is a 10x increase in the concentration of H+ in a solution
- pH 2 has 10x more H+ ions than pH 3

Question 24

pH of Pure Water

Answer 24

pH of 7.0
- Neither acidic or basic
- Amount of H+ and OH- are equal

Question 25

pH level in most of our cells

Answer 25

Close to pH of 7.0

Question 26

pH level of human blood

Answer 26

pH of 7.4
- Human will die if it goes lower than 7.0 or higher than 7.8

Question 27

Buffer

Answer 27

Substance that minimizes changes in pH
- Accepts H+ when there’s extra, and donates H+ when depleted