Chap 1: Water in Our Daily Lives

Question 1

unicellular organisms that lives in the water

Answer 1

• Chlamydomonas
• Paramecia

Question 2

physical properties of water

Answer 2

• colourless
• odourless
• tasteless
• boiling point at 100°C
• freezing point at 0°C

Question 3

explain why the water droplet is spherical-shaped

Answer 3

the interacting attractive force between interfacial molecules make the interface to behave like a stretched elastic membrane (surface tension)

Question 4

what is capillary action?

Answer 4

the movement of a liquid through a narrow space without the assistance of external forces

Question 5

what is adhesion?

Answer 5

one substance attracted to another substance

Question 6

what is cohesive?

Answer 6

same molecules attracted to each other

Question 7

phenomena of capillarity in the nature

Answer 7

• absorption of water by bricks
• adsorption of sweat by towels
• absorption of ink by chalks

Question 8

What is the use of anhydrous cobalt chloride and anhydrous copper sulphate?

Answer 8

to test the presence of water

Question 9

Anhydrous cobalt chloride

Answer 9

• blue to pink
• can be reused after drying

Question 10

Anhydrous copper sulphate

Answer 10

• white to blue
• used as a drying agent to absorb moisture

Question 11

what are
* surface runoffs:
* infiltration:
* underground runoffs:
* transpiration:

Answer 11

• surface runoffs: water that flows from higher ground to lower ground
• infiltration: water that slowly penetrates the pores and cracks of soil and rocks, and flows downwards to become groundwater
• underground runoffs: water that is stored underground and enters the river and seas
• transpiration: absorbed by the roots of plants and becomes water vapour

Question 12

states or phases of the water cycle

Answer 12

evaporation/ transpiration/ sublimation(ice) → condensation → precipitation (desublimation) → infiltration/ runoffs/ underground runoffs

Question 13

how does water undergo chemical change?

Answer 13

electrolysis of water

Question 14

what is added while doing the electrolysis of water?

Answer 14

sulphuric acid, to increase the conductivity of water

Question 15

properties of oxygen gas

Answer 15

• rekindles a glowing splint
• used anode +

Question 16

properties of hydrogen gas

Answer 16

• burns with blue flame
• produces a ‘pop’ sound (if mixed with a little oxygen)
• uses cathode -

Question 17

structure of water molecule

Answer 17

one oxygen atom and two hydrogen atoms (H₂O)

Question 18

natural water is __________________________

Answer 18

purified before consumed by public

Question 19

microorganisms living in natural water

Answer 19

• algae
• protozoa
• bacteria

Question 20

effects of microorganisms

Answer 20

• becomes dark and smelly
• when it rains, the river that contains soil and sand makes it turbid