Example Question
"Rutherford designed an experiment to see what happened when alpha particles were directed at a piece of gold foil. Summarise the observations and state the conclusion Rutherford reached about the structure of gold atoms. (5)"
What was the experiment?
Alpha particles were shot at a very thin sheet of gold foil only a few atoms thick. This was done to find out how the charge was distributed, the prevailing theory at the time was a plum pudding model where positive and negative charge was mixed around like vegetable soup.
What happened?
As expected, most alpha particles went straight through.
But some were deflected, and a few deflected at large angles which didn't fit very well into the previous theory. I think Rutherford himself remarked that it was almost as incredible as if you'd shot a piece of tissue paper with a .50" calliber rifle and the shots rebounded right back at you.
For context, it was less than 1% of alpha particles that deflected right back.
What could be concluded?
Most alpha particles went straight through with no deflection, so it must be mostly empty space because if something was in the way then deflections would occur.
Most of the mass must be very small/dense, because if it was big then a larger proportion will be deflected.
The nucleus must be charged to cause small angle deflections.
The nucleus must contain most of the mass as interactions with the electrons allow the alpha particles to pass right through
Exam answers
Observations
Most alpha particles went straight through (1)
Some were deflected (1)
Few deflected at large angles (1)
Conclusions
Mainly empty space (1)
Nucleus must be very small/dense (1)
Nucleus must be charged (1)
Nucleus contains most of the mass (1)
If you answer in a longer, more descriptive/essay-based way instead of summarizing the key points then you're losing time efficiency (this particular question should take no more than 5 minutes, if you're stuck for more than 2 minutes you should move on and come back when it becomes a little clearer in your head).
This kind of systematic approach is essential for exam success.