Student book answers
Chapter 2
C3 2.1 Evidence for atoms
In-text questions
A They used creative thought.
B Each element has its own type of atom, the atoms of different elements have different
masses, compounds form when atoms of different elements join together, and atoms are
rearranged in chemical reactions.
Atoms and evidence
Script to include the ideas of Dalton and Democritus, including the point that
Dalton found experimental evidence for atoms, while Democritus did not carry out
experiments. He worked out his answers using creative thought.
Activity
Summary
questions
1 small, empty space, mixed up (3 marks)
2 Dalton read about the work of Lavoisier, who had discovered that air includes two gases.
The discovery got Dalton thinking about how the gases in air could be mixed up, and
encouraged Dalton to carry out experiments of his own. (2 marks)
3 QWC question (6 marks). Example answers:
Democritus and Dalton both stated that everything is made from atoms.
Democritus worked out his ideas using creative thought alone.
Dalton collected experimental evidence to support his ideas.
When developing and planning his investigation, Dalton drew on evidence from other
scientists, including Lavoisier.
Lavoisier had already discovered that air contains a mixture of gases.
Dalton developed his model further than Democritus, for example, by pointing out that
water vapour and air are made of separate particles, which mix together when water
evaporates.
C3 2.2 Looking into atoms
In-text questions
A As a billiard ball.
B A tiny particle that is a part of an atom. It has a negative charge and a tiny mass.
C In an atom there is a positively charged sphere in which negative electrons are
moving around.
Activity
How massive?
mass of oxygen atom nucleus = 16
mass of electron = 0.0005
16 ÷ 0.0005 = 32 000
The mass of an oxygen atom nucleus is 32 000 times greater than the mass of an
electron.
© Oxford University Press 2014 www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
Student book answers
Chapter 2
Summary
questions
1 ball, pudding, negative, nucleus, positive (5 marks)
2 Rutherford and colleagues fired positive particles at a piece of gold foil. Most
particles went straight through the foil, through the empty space. A few particles
bounced backwards from the foil, which surprised Rutherford. These particles must
have bounced off a positively charged central nucleus that contains most of the
mass of the atom. (4 marks)
3 Chart should include the following (6 marks):
Billiard ball model (Dalton): Atoms are unique to each element. An atom is like a
billiard ball and cannot be broken up.
Plum pudding model (Thomson): A positively charged sphere with negative electrons
moving around in it. Deduced from Thomson’s experiment with cathode
rays/charged gases that glowed. Cathode rays were negative, and originated from
the atom. This meant that there must be a positive part of the atom.
Planetary model (Rutherford, Geiger, and Marsden): Atoms have a central positively
charged nucleus that contains almost all of the mass. The rest of the atom is empty
space, where electrons orbit the nucleus.
Evidence for this model was observed when firing positive (α) particles at gold foil,
when a few particles curiously bounced back off the foil, back in the original direction
that the particle was fired from.
C3 2.3 Discovering the Periodic Table
In-text questions
A Mendeleev
B He left gaps for elements he thought existed but had not been discovered.
C (Ida) Tacke, (Walter) Noddack, and (Otto) Berg
Activity
Mendeleev’s musings
Script to include the following main points about the first Periodic Table: elements
arranged in order of atomic mass, elements with similar properties grouped together,
gaps left for elements that Mendeleev predicted should exist but that had not yet
been discovered. The script should convey Mendeleev’s excitement and confidence.
Summary
questions
1 masses, physical, oxygen, mass, similar (5 marks)
2 Tacke and Noddack extracted 1 g of a new substance from 660 kg of an ore. They
thought that this substance might be one of the missing elements under manganese
on the Periodic Table (that was not yet discovered). They asked Berg to do tests on
the substance to confirm its identity. (This is like peer review. Tacke and Noddack
asked a different scientist to check the reproducibility of their work.) (3 marks)
3 QWC question (6 marks). Example answers:
Mendeleev obtained atomic mass data from Cannizzaro.
Mendeleev then made a set of cards, one for each element.
He tried sorting the cards in different ways.
He came up with an arrangement that worked – by arranging the cards in atomic
mass order.
Mendeleev grouped elements with similar properties.
Mendeleev left gaps for elements he predicted should exist but that had not yet been
discovered.
These were later confirmed when scientists discovered the missing elements.
© Oxford University Press 2014 www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
Student book answers
Chapter 2
C3 2.4 Lessons from fossils
In-text questions
A Fossils are the remains, or traces, of plants or animals that lived many years ago. They
have been preserved by natural processes.
B The relative age of a rock.
Activity
Explaining explanations
Flow diagrams should include the following stages:
Asking a question – why do different rock strata contain different fossils?
Suggesting an explanation – perhaps rock strata of the same age always contain
fossils of the same species.
Testing the explanation – evidence collected by making observations in rocks of
different ages and in different places.
Summary
questions
1 traces, plants, natural, sedimentary, strata (5 marks)
2 An animal dies and is covered by mud or sand. Bacteria break down the soft tissues of
the organism.
The mud or sand surrounding the skeleton becomes rock. Minerals from underground
water replace those in the skeleton, leaving a fossil. (4 marks)
3 Poster should include the following scientific points (6 marks):
 how fossils were made
 different types of rocks
 understanding the relationship between different strata and geological ages
 diet of extinct species
 evolution of species.
C3 2.5 The oldest primate
In-text questions
A A collection of articles written by scientists about their research.
B So that scientists in France could use a new technique to study the fossil.
C Its skull had relatively small eye sockets.
Activity
Family tree
Explanation of the primate family tree should include the following key points:
Lemurs, lorises, adapids, tarsiers, Archicebus achilles, humans, apes, and monkeys
all have a common ancestor. Its descendants split into groups. One group became
the monkeys, apes, and humans that we know today. The second group later split
further, leading to the evolution of lemurs and lorises from the now-extinct adapids.
The final group divided into two further groups – the now-extinct Archicebus achilles,
and tarsiers.
© Oxford University Press 2014 www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
Student book answers
Chapter 2
Summary
questions
1 humans, journal, reviewed (3 marks)
2 Archicebus achilles had small pointy teeth. Sharp teeth were adapted for eating
insects. (2 marks)
3 QWC question (6 marks). Example answers:
The first primates were not the size of modern monkeys, as previously thought.
This was because the fossil of Archicebus achilles measured 71 mm in length.
Instead the first primates were smaller mammals that scurried through rainforest
canopies.
The skull of Archicebus achilles had small eye sockets, suggesting it was active in
daylight.
Its teeth were sharp, suggesting that its diet consisted of insects.
Scientists say that Archicebus achilles is an ancestor of the modern tarsier.
Scientists also hypothesise that the first humans may not have evolved in Africa,
as previously thought, but instead in Asia.
Primates also split into two groups (tarsiers, and the group including monkeys,
apes, and humans) up to
10 million years earlier than previously thought.
C3 Chapter 2 summary
End-of-chapter
questions
1 B, C, A, D (4 marks)
2 atoms, nucleus, positively, negatively (4 marks)
3 Ask a question: Y
Suggest an explanation: Z
Test the explanation: X (3 marks)
4 This is a QWC question. Students should be marked on the use of good English,
organisation of information, spelling and grammar, and correct use of specialist scientific
terms. The best answers will fully review Dalton’s ideas in the text provided (maximum
of 6 marks).
Examples of correct scientific points:
It is not strictly correct to state that gas particles are surrounded by heat.
An improvement would be to state that the gas particles move around continuously
(Brownian motion).
The movement of particles causes friction, which can result in an increase in
temperature.
In the gas state, the particles are not touching each other, as stated by Dalton.
Dalton was also correct to say that particles do not settle down into separate groups.
Dalton was also correct to say that different gases have their own types of atoms.
However, Dalton said that the greater the mass of 1 m3 of gas, the heavier its atoms.
We now know that gases can exist as pure gases, but also as mixtures of compounds
and molecules.
This means that more than one type of atom can exist in any one gas.
Dalton’s statement would be improved by stating that ‘the greater the mass of 1 m 3 of
gas, the heavier its particles.
Particles can be used to describe both atoms and molecules.
© Oxford University Press 2014 www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
Student book answers
Chapter 2
Answer guide for Case Study
1–2 marks
Developi
ng
● A poorly organised table giving
Secure
Extending
3–4 marks
5–6 marks
● A reasonably well-organised
● A clearly organised table giving
one example to illustrate the
table giving one or two
examples to illustrate all three
following stages of developing an
examples to illustrate the
stages of developing an
explanation: asking a question,
following stages of developing
explanation: asking a question,
suggesting an explanation, and
an explanation: asking a
suggesting an explanation, and
testing the explanation.
question, suggesting an
testing the explanation.
● An outline lesson plan is provided.
explanation, and testing the
explanation.
● A lesson plan is provided that is
designed to be exciting.
● A lesson plan is provided that
includes clear objectives and
outcomes.
● Lesson plans should also be
designed to be engaging and
exciting.
© Oxford University Press 2014 www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.