Answer: TWO.
At least two groups: treatment group and control group.
The treatment group is that is exposed to the different levels of the independent variable ( a medication for example), while the control group is not treated, so the researchers can compare the effect of the medication.
A catalyst is a substance that speeds up a chemical reaction.
Answer:
matter can either be created nor destroyed but can be transmitted fromone state to another state
Answer:
Electric engines have efficiencies of roughly 90% whilst combustion engines about 10% to 30%. This is because combustion engines emit much more heat, which is always energy that is not used as work, and thus increases inefficiency.
Explanation:
