Term 3 Ace

Observations before

The potato in the Salt water solution

                               i.            The slice of the potato was floating near the surface of the water

                             ii.            Its diameter is 4.2 cm

The potato in the Sugar water solution

                               i.            The slice of the potato floated in the middle of the cup

                             ii.            The diameter of the potato is 4.2 cm

The potato in the Plain water

                               i.            The slice of the potato was at the bottom of the cup

                             ii.            The diameter of the potato is 4.2 cm

Observations after an hour

The potato in the Salt water solution

                               i.            After an hour, there were air bubbles form on the surface of the water

                             ii.            The slice of potato sank to the bottom of the cup after an hour

                          iii.            The slice of the potato had turned a little darker

                          iv.            The size of the potato has decreased it shrank by 0.3 cm

                             v.            It turned more flexible and soft

The potato in the Sugar water solution

                               i.            The potato sank to the bottom of the cup after an hour

                             ii.             The potato turned smaller a little

                          iii.            It also became a little softer but not as much as the on in the Salt water solution

                          iv.            The size of the potato remained the same, as it is still 4.2 cm.

The potato in the Plain water

                               i.            The potato remained at the same place it did not sink or float

                             ii.            It turned larger by 0.2cm

                          iii.            It became more rigid than it was at the start

 

	The potato in the Salt water solution	The potato in the Sugar water solution	The potato in the Plain water
BEFORE AFTER	4.2 cm 3.9 cm	4.2 cm 4.2 cm	4.2 cm 4.4 cm

Why did that happen? It has to do with a process called osmosis. The potato is made up of tiny, living units called cells. Each cell is surrounded by a cell membrane which acts much as your skin does. It keeps the cells parts inside and keep other things outside, protecting the cell. While this membrane stops most things, water can pass through it. The water tends to move towards higher concentrations of dissolved chemicals. That means that if the water outside the cell is saltier than the water inside, water will move from the inside of the cell to the outside. That is what happened to the slice of potato in the salt water. As the water left the cell it was much like letting the air out of a balloon. As more and more of the cells lost water, the slice of potato became soft and flexible. The same thing happened for the sugar, but since the cells in the potato contain more sugar than they do salt, the cells did not get as soft.

When you put the potato into the plain water, the reverse happened. Water moved from the outside, where there was no salt or sugar, into the cell where there was some. This caused the cells to swell up, becoming very stiff.