When the concentration is expressed in mass percentage, that means there is 3 g of solvent H₂O₂ in 100 grams of the solution. Then, that means the remaining amount of solute is 97 g. We use the value of molarity (moles/liters) to determine the amount of solution in liters, denoted as V. The solution is as follows:
0.02 mol KMnO4/L solution * 158.034 g KMnO4/mol * V = 97 g KMnO4
Solving for V,
V = 30.69 L
He is missing a (real) control. Growing two plants without plant food at all doesn't count; in order to see if the new food is better, he must also grow plants with the original food in order to compare it.
He does have an independent variable. This is the type of plant food. It's independent because he has direct control over it.
He needs to give plants the same conditions besides food: same water (amount), same light exposure, same temperature, etc.
He needs to choose a quantitative way to measure how much the plants grew, like mass or length.
For 23., you have to find a way to measure your heart rate not increase it. search it up on google.
The control room is similar to the nucleus, because the nucleus is in charge of cell functions.
