SA2 FOCUS · Atoms & Reactions
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Secondary 1 · SA2 Topic Focus · Section C

Atoms &
Chemical Reactions

Atomic structure · Exo/Endothermic · Temp changes
15 questions · self-marked · drill until 100%

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FuseSchool · What Is An Atom? FuseSchool · Endo & Exothermic Reactions BBC Bitesize · Atoms & Elements Rutherford's Gold Foil Experiment More videos →
⚛ Atomic Structure 🔥 Exo & Endothermic 🌡 Temperature Changes
⚛
Part 1

Atomic Structure

The atom: a tiny positive nucleus (protons + neutrons) in the centre, with negative electrons in shells around the outside. The atom is mostly empty space.
Q1
In the Rutherford model of the atom, where is the nucleus?
1 mark
In the centre of the atom
Spread evenly throughout the atom
On the outer edge of the atom
In the electron shells, orbiting at a distance
Q2
What charge does the nucleus carry?
1 mark
Positive
Neutral (no charge)
Negative
It changes all the time
Q3
The nucleus contains protons and neutrons. Where are the electrons found?
1 mark
Inside the nucleus with the protons
Floating outside the atom completely
In shells (orbits) around the nucleus
Only in metals, not in other atoms
Q4
What charge does an electron carry?
1 mark
Q5
In Rutherford's gold foil experiment, most of the tiny particles fired at the foil passed straight through. What does this tell us about the atom?
2 marks
The atom is a solid ball with no gaps
Gold does not contain atoms
Atoms are negatively charged all over
The atom is mostly empty space, with its mass concentrated in a tiny central nucleus
Q6
Why is an atom neutral overall (no overall charge)?
1 mark
It has no charged particles at all
It has equal numbers of positive protons and negative electrons, so the charges cancel out
The neutrons make everything positive
Electrons are stronger than protons
ATOMIC STRUCTURE — SECTION SCORE
0/7
🔥
Part 2

Exothermic & Endothermic

Memory trick: Exo = exit → heat leaves, surroundings get hotter. Endo = into → heat is absorbed, surroundings get colder.
Q7
In an exothermic reaction, what happens to the temperature of the surroundings?
1 mark
It increases then disappears
It decreases — heat energy is absorbed
It stays exactly the same
It increases — heat energy is released
Q8
In an endothermic reaction, what happens to the temperature of the surroundings?
1 mark
It increases — heat is released
It stays the same
It decreases — heat energy is absorbed from the surroundings
It first rises then falls
Q9
When magnesium reacts with hydrochloric acid, the temperature rises. Is the reaction exothermic or endothermic, and why?
2 marks
Endothermic, because heat is absorbed
Exothermic, because the temperature increased — heat energy was released
Endothermic, because the temperature increased
Exothermic, because the temperature decreased
Q10
Which of these is an example of an endothermic change (it takes heat IN and feels cold)?
1 mark
A campfire burning wood
A hand-warmer that heats up
A sports cold-pack that goes cold when you snap it
Magnesium reacting with acid and warming up
EXO & ENDOTHERMIC — SECTION SCORE
0/5
🌡
Part 3

Temperature Change Calculations

Temperature change = end temperature − start temperature. A positive answer = heated up (exothermic). A negative answer = cooled down (endothermic).
Q11
An experiment starts at 21 °C and ends at 34 °C. Calculate the temperature change.
1 mark
°C
Q12
A second experiment starts at 22 °C and ends at 36 °C. Calculate the temperature change.
1 mark
°C
Q13
In a reaction the temperature falls from 25 °C to 18 °C. What is the size of the temperature change?
1 mark
°C
Q14
The temperature in Q13 went down. What type of reaction is it?
1 mark
Endothermic
Exothermic
Neither — temperature change never shows the type
Both at the same time
Q15
Chen adds magnesium to acid and records the temperature every 10 seconds until the reaction stops. Which statement best describes the temperature trend?
2 marks
Temperature decreases steadily throughout
Temperature rises quickly at first, then the rise slows, then levels off as the magnesium is used up
Temperature stays the same the whole time
Temperature stays constant then suddenly drops
TEMPERATURE CHANGES — SECTION SCORE
0/6
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