Matter

Question 1

What happens when a strip of paw paw is placed in water- Osmosis

Answer 1

The membranes of living cells are differentially permeable and the cytoplasm inside the cells contains about 80% water.
* When a strip of living tissue (such as paw-paw) is placed in water, water molecules move into the cells by osmosis.
Each cell swells slightly, and the strip increases in length and becomes rigid(hard).

Question 2

What happens when a strip of paw paw is placed in concentrated nacl/salt solution- Osmosis

Answer 2

When the strip is placed in a concentrated sodium chloride solution, water molecules move out of the cells by osmosis.
Each cell shrinks slightly, and the strip decreases in length and becomes
softer.

Question 3

Uses of osmosis- To control garden pests

Answer 3

Slugs and snails are garden pests, whose skin is differentially permeable and always moist. When salt (sodium chloride) is sprinkled on slugs and snails, it dissolves in the moisture around their bodies forming a concentrated solution. Water inside their bodies then moves out by osmosis and into the solution. The slugs and snails die from dehydration if their bodies lose more water than they can tolerate.

Question 4

Uses of osmosis- to preserve food

Answer 4

Salt and sugar are used to preserve foods such as meat, fish and fruit. They both work in the
same way:

• They draw water out of the cells of the food by osmosis. This prevents the food from decaying
  because there is no water available in the cells for the chemical reactions which cause
  the decay .
• They draw water out of microorganisms (bacteria and fungi) by osmosis. This prevents the food
  from decaying because it inhibits the growth of the microorganisms that cause the decay.