Water

Question 1

how do we tell if water is soft or hard?

Answer 1

soft water will produce a lather if mixed with soap.

Question 2

what does hard water contain?

Answer 2

magnesium and calcium compounds, dissolved in the water.

Question 3

magnesium and calcium ions make the water what?

Answer 3

hard water.

Question 4

scum is an insoluble precipitate made how?

Answer 4

with hard water and soap.

Question 5

washing powder will make what happen from hard water?

Answer 5

make scum stick to clothes.

Question 6

benifits of hard water is

Answer 6

• bone development
• teeth development
• reduction in heart disease

Question 7

what is the difference between temporary hard water and permanent hard water?

Answer 7

temporary - can be softened by heating

permanent - remains hard even after being boiled or heated.

Question 8

how can we use washing soda to soften water.

Answer 8

use sodium carbonate(washing soda) to produce CaCO3 + Na

Question 9

ion exchange columns use sodium to do what?

Answer 9

the sodium or hydrogen is exchanged in the resin with calcium or the magnesium.

Question 10

hard water contains hydrogencarbonate ions.

Answer 10

hydrogencarbonate ions decompose to form carbonate ions, they then react to magnesium or calcium

Question 11

scale is also known as what?

Answer 11

lime scale.

Question 12

screens in purifying water does what?

Answer 12

remove debris in the water.

Question 13

settlement tanks do what?

Answer 13

sand and soil settle out at the bottom of this container.

Question 14

coagulation does what?

Answer 14

aluminium sulfate makes particles of dirt stick together and settle

Question 15

filter bed does what?

Answer 15

filters very fine sand and insoluble solid particles

Question 16

chlorine is added at the end to do what?

Answer 16

kill bacteria.

Question 17

flourine is some areas for whatm

Answer 17

hardens teeth

Question 18

what are the arguments for and against adding flourine to water?

Answer 18

For:
- Reduces tooth decay
- only in tiny amounts
Against:
- possible links with learning difficulties
- unethical.

Question 19

filters in the home often use what?

Answer 19

carbon - to remove chlorine levels or possible other chemicals.