-Make sure you say what you mean.
Be careful with commonly confused words:
Temperature has an effect on the reaction.Temperature affects the reaction.I used solutions in various concentrations. (The solutions were 5 mg/ml, 10 mg/ml, and 15 mg/ml)
I used solutions in varying concentrations. (The concentrations I used changed; sometimes they were 5 mg/ml, other times they were 15 mg/ml.)Less food (can't count numbers of food)
Fewer animals (can count numbers of animals)A large amount of food (can't count them)A large number of animals (can count them)The erythrocytes, which are in the blood, contain hemoglobin.
The erythrocytes that are in the blood contain hemoglobin. (Wrong. This sentence implies that there are erythrocytes elsewhere that don't contain hemoglobin.)