Unit 15- Air and water

Question 1

Give three main substances in the air and their percentage

Answer 1

Nitrogen 78%, oxygen 21%, argon about 1%

Question 2

How to measure the percentage of oxygen in the air

Answer 2

step 1) connect a syringe with a 100cm cube of air with an empty syringe, and the tube containing copper wire in between them.
step 2)Heat the tube containing copper using a bunsen burner and push the air to another syringe. Then push it back. Repeat the process for about 3 mins.
step 3) then stop heating the tube. Push all the gas on one side and measure its volume.
step 4) repeat step 2 and 3 until the volume of the remaining gas is steady.
step 5) final volume/ starting volume( 100cm cube) then times the value by 100.

Question 3

state how to separate nitrogen from the air

Answer 3

Fractional distillation

Question 4

Why is carbon monoxide a harmful gas

Answer 4

Reacts with the haemoglobin in blood, and prevent it from carrying oxygen around the body.

Question 5

Why is sulfur dioxide a harmful gas

Answer 5

Irritates the eyes and throat
cause respiratory problems
form acid rain

Question 6

Why is nitrogen oxides a harmful gas

Answer 6

cause respiratory problems

from acid rain

Question 7

why is lead compounds a harmful gas

Answer 7

damages the kidney and nervous system

Question 8

How does catalytic converter works

Answer 8

the harmful gases are absorbed onto the surface of catalysts, where they react to form harmless gases. The catalysts speed up the reaction

Question 9

Rusting requires ____ and ____

Answer 9

oxygen and water

Question 10

what is rusting

Answer 10

corrosion of iron and steel

Question 11

What kind of iron does not rust

Answer 11

the alloy stainless steel

Question 12

What is galvanising

Answer 12

coating zinc on the other metal

Question 13

What is sacrificial protection

Answer 13

allowing one metal( more reactive one) to corrode, in order to protect another metal ( less reactive one)

Question 14

The test for pure water

Answer 14

boil at 100 degree Celcius and freeze at 0 degree celcius

Question 15

describe the process of water treatment

Answer 15

Water is pumped in
A coagulant is added to make small suspended particles stick together - coagulant
then it goes through a flotation tank to separate coagulated particles - flotation tank
The water is passed through a bed of fine sand to filter it - sand filter
Go through charcoal to remove bad tastes and smells - charcoal
CHLORINE is added to kill the bacteria and other microbes - chlorine
stored in the storage - stroage