science practical 2.0

Question 1

what is osmosis

Answer 1

It is the net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a selectively permeable membrane.

Question 2

what are the keywords for describing the process of osmosis

Answer 2

• osmosis occured
• state process responsible for observation e.g. leek cells possess a lower water potential compared to distilled water
• state difference in water potential between the 2 regions
• hence net movement of water molecules across selectively permeable membrane

Question 3

3 formulas for acids

Answer 3

Acid + reactive metal=hydrogen gas + salt
Acid + carbonate=salt + water + carbon dioxide
Acid + alkaline= salt + water

Question 4

Key points when recording observations (Adding solutions)

Answer 4

• colour of precipitate
• colour change in solution
  e. g. A white precipitate is formed/red solution turned green

Question 5

Key points when recording observations (Test for gas)

Answer 5

• effervescence
• colour of gas
• smell of gas
• specific test for gas
  e. g. Effervescence of colourless and odourless gas is observed. Gas formed white precipitate when bubbled into limewater

Question 6

Describe test for gas (hydrogen)

Answer 6

Place a lighted splint at the mouth of a test tube, the gas will extinguish the lighted splint with a ‘pop’ sound

Question 7

Describe test for gas (carbon dioxide)

Answer 7

Bubble the gas into limewater. White precipitate will be formed in limewater

Question 8

Key points when recording observations (Heating of solid)

Answer 8

• Change in colour of solid (before and after heating)
• Change of state
• Colour of residue on cooling (may be different when hot)
  e. g. Green powder decomposes to form black solid/Solid Y melts to form a yellow liquid/a white residue remains

Question 9

Key points when recording observations (Adding solid to solutions)

Answer 9

• Solubility of solid in water
• Colour of solution formed
  e. g. Yellow solid dissolves to form a yellow solution/yellow soldi remained insoluble

Question 10

Key points when recording observations (Using universal indicator)

Answer 10

• Colour change of Universal Indicator

e. g. Green universal indicator turns red

Question 11

“No chemical reaction.” Is this correct?

Answer 11

No. We should write “no visible change/reaction”.

Question 12

what is diffusion

Answer 12

It is the net movement of particles from an area where they are at a higher concentration to areas where they are at a lower concentration due to the random movement of the molecules

Question 13

keywords for describing gas

Answer 13

• colour and odour of gas