Can someone pleeease help me with this..
I get confused between independent and dependent variables.
Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?
If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?
Thanks!!
In an experiment, for eg the potato experiment, in order to get the diluted and concentrated solution, you must add salt to each beaker, hence, you can change the concentration of salt whatever you want, you can add more, you can add less, it's all up to you. Hence, we call the concentration of salt the INDEPENDENT VARIABLE. Since the external environment will determine the net movement of wAter in or out of the potatoes cells, we call the net movement of water the DEPENDENT VARIABLE since it is caused by the concentration of substrate outside. In practice, it is actually really hard to make sure that all the other variables constant and ONLY the independent and dependent variables that change,hence, we have to minimize as much as possible the changes in all other variables except independent and dependent variables.
A good hypothesis is all about making a measurable and observable hypothesis, you have to be specific about your quantities. Hypothesis is usually an " If....then..." statement. Hence, my possible hypothesis for this is, " If the concentration of salt on the external environment changes in an addition of 2.5% then, there will be a net movement of water from the potato cells to the external environment (a hypertonic environment) by osmosis effect, hence, there will be a decrease in mass of the potato due to the loss of water content"
Hope this helps.