Osmosis

What is the definition of osmosis?

What is the definition of osmosis?

the movement of water particles across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

What is a partially permeable membrane?

A membrane with small holes in it to allow tiny molecules to pass through it

How does osmosis work?

• Water molecules pass through both ways of the membrane because water molecules move around randomly all the time

• Because there are more water molecules on one side than the other, there’s a steady net flow of water into the region with fewer water molecules

• This causes the stronger sugar solution to get more dilute

Explain an experiment to observe how sugar solutions affect plant tissue.

1. Cut up a potato into identical cylinders and get 2 beakers with different sugar solutions. One should have pure water and another should have a very concentrated sugar solution

2. Measure the mass of the cylinders and then leave one cylinder in each beaker for about 24 hours

3. Take them out and dry them with a paper towel and measure their masses again

4. If the cylinders have drawn in water with osmosis, they’ll have increased in mass, and if water has been drawn out the mass will have decreased

What is the independent variable for the experiment to observe how sugar solutions affect plant tissue due to osmosis?

The concentration of the sugar solution

What is the dependant variable for the experiment to observe how sugar solutions affect plant tissue due to osmosis?

The potato cylinders mass

What are the main controlled variables for the experiment to observe how sugar solutions affect plant tissue due to osmosis?

• same volume of solution

• Same temperature

• Same time in solution

• same type of sugar used

What are some possible errors for the experiment to observe how sugar solutions affect plant tissue due to osmosis?

• if the potato cylinders weren’t fully dried, the excess water would give it a higher mass

• if water evaporated from the beakers, the concentrations of the salt solutions could change

How could you reduce the effect of possible errors for the experiment to observe how sugar solutions affect plant tissue due to osmosis?

• Repeating the experiment and calculating the mean percentage change at each concentration