Chapter 5 Leaners book answers.

Topic 5.1 The structure of the atom

Questions
1 proton
2 electron
3 protons and neutrons
4 No charge; they balance each other out.
5 The individual atoms are held together by electrostatic attraction between the positively
charge protons and the negatively charged electrons.
6 Thompson’s model of the atom has no nucleus, unlike the model we use today.
7 J. J. Thompson discovered the electron in the 1890s. 8 James Chadwick proved the neutron
existed in 1932.
9 Ernest Rutherford discovered the proton in 1909 and the nucleus in 1911.
10 Rutherford’s model of the atom has a nucleus but it doesn’t have any neutrons in it because
neutrons had not been proved to exist when his model was formed.
Topic 5.2 Purity
1 37.5%
2 90%
3 boron
4 nitrogen, nickel or hydrogen.
5.
Think like a scientist: Finding the mass of salts in seawater
1–3 This will depend on their experiment.
4 There should be some similarity between the results obtained and those suggested in the
Learner’s Book. If not, suggestion might be: different seawater samples, spilling some of the
seawater or other practical issues.
5 This is dependent on what they did and any attempts they made to address these difficulties.
6 • Wearing safety glasses.
• Care when heating in the evaporating basin as the solution may spit.
• Care when moving the hot evaporating basin or heating equipment.

Think like a scientist: Reactions with more than one product

1 These should be specific to what the learners have done in the practical. Ensure word
equations are written on one line.
2 Look for suggestions, such as where there is a solid and liquid formed, filtering (to obtain the
liquid) and collecting and drying (to obtain the solid) for example silver nitrate and sodium
chloride. Evaporating the solution; for example, in a neutralisation reaction. The suggestions
are the important thing based on the knowledge they have. The suggestion does not need to be
what you would do but it needs to be discussed in class.
3 Specific suggestions for each reaction or general suggestions, such as care with acids and
alkalis; not spilling liquids; any spills cleared up at once; replacing bottle stoppers as soon as
possible; bottle tops placed upside down on the work surface; any spills on the skin washed
with water; wearing safety glasses.
Topic 5.3 Weather and climate
1 Scotland: The weather is cold, there is snow on the ground. There is no precipitation. It is
cloudy. Namibia: The weather must have very little rain as there is only sparse vegetation. The
sun is shining as you can see shadows. There are white clouds in the distance.
New Zealand: The weather is wet; it is raining heavily. The sky is cloudy and dark. Canada: The
sky is grey with low cloud or mist above the trees.
Republic of Ireland: There are many white clouds in the sky but the sun is shining, you can see it
on the grass. There is a rainbow.
Bangladesh: It is very windy and the branches of the trees are bent over in the wind. The sky is
grey.
2 So that we can use the information to build up a picture of what is likely to happen in the
future.
3 This will depend on where you live.
4 Credit any correct answers, such as Mali, Chad, Oman, Saudi Arabia, and Yemen.
5 Credit any correct answers, such as S/SW Australia, central Chile, the Western Cape, SW of
USA.
6 Credit any correct answers, such as Cameroon, Democratic republic of Congo, Uganda, Brazil,
Columbia, Malaysia, Indonesia, Thailand, Costa Rica, Cuba and Jamaica.
7 The climate in the arid zone is hot and dry all year, whereas the climate in the tropical zone is
hot and wet all year.
8 The climate in the temperate zone has cold winters and mild summers, whereas the
Mediterranean zone has mild winters and hot, dry summers.
Activity: Recording the weather
1 So that a comparison can be made. The temperature tends to be higher in the middle of the
day, so if you took the temperature at 9 am and the next day at 2 pm you would not be
comparing the same thing.
2 So that they are not affected by direct sunlight. On one day it may be cloudy and the Sun not
visible, and on another day, direct sunlight on the thermometer would affect the reading, so
you would not be comparing the same thing.
3 The report should reflect what learners have found and account for temperature,
precipitation (even recorded as zero, if appropriate) wind speed and direction, cloud cover,
humidity, visibility, and so on. The measurements and observations should be presented in an
appropriate way.
4 The line graph should be drawn to an appropriate scale and accurately plotted to show the
changes in temperature over the week. Temperature should be plotted on the vertical axis and
the date along the horizontal axis.
5 In the comparisons, there are likely to be minor differences in the temperature readings, due
mainly to where they were taken and how accurately they can use the thermometer. Other
observations where it is a matter of opinion, such as cloud cover, are likely to show greater
variation. Learners should recognise the difference between accurate measurements and the
more descriptive assessments. They should question the method used by each group, the
timing and whether they used the same apparatus.
6 Data should be available via the internet or local television. Comparisons are likely to be
difficult as learners do not know exactly where the measurements or observations were taken
and they are unlikely to be measured in the same way or at the same time. The measurements
will be the averages of many readings taken at different sites and times. So the differences
between the learners’ data and national data will be down to these factors as well as the more
accurate measurements taken by professionals and the more accurate methods for taking the
measurements and the standardisation of observations.

Topic 5.4 Climate and ice ages

Activity: Where in the World is there ice?
1 Credit any correct country or area that can be identified by comparing a current world map
with that in the Learner’s Book.
2 The parts of the world that are covered in ice are all either a long way from the equator or on
the top of high mountains.
Questions
1 five
2 Yes, because an ice age is when there is permanent ice somewhere on Earth and there is
currently permanent ice at the poles and on some mountains and glaciers.
3 An ice age is when there is some permanent ice somewhere on the Earth. In an ice age, there
are periods when most of the Earth is frozen, that is a glacial period.
4 No, we are in an interglacial period with ice only at the poles, on some mountains and
glaciers.
5 Accept any glacier locations that are correct; answers will depend on your location.
6 Learners should provide evidence, such as marks on the rock, U-shaped valleys as opposed to
the V-shaped valley a river would make, deposits of large boulders and other rocks.
Questions
1 The early atmosphere was formed from the gases that the many volcanoes produced.
2 Any two differences, such as: there was very little oxygen in the early atmosphere, but today
about 20% is oxygen; there is very little carbon dioxide in the atmosphere today (about 0.04%)
but the early atmosphere was about 80% carbon dioxide; there was very little nitrogen in the
early atmosphere (2.5%) now there is almost 80%.
3 There was very little oxygen in the early atmosphere. It was not suitable for humans or other
animals because they need oxygen to respire.
4 Fossil fuels are those that have been formed from plants and animals that did not rot when
they died. They have carbon locked up in them.
5 Microorganisms and plants developed over many millions of years and they used the carbon
dioxide to produce food. The plants produced their food by the process of photosynthesis.
6 There is evidence that the oxygen levels increased because there are rocks where iron has
combined with oxygen to form red iron oxide. These rocks date from about 2 billion years ago.
7 carbon and oxygen
8 calcium, carbon and oxygen
9 Limestone is formed when the shells of dead sea creatures fall to the bottom of the ocean
and over millions of years these layers become compressed into rock.
10 About 3500 million years ago.

Check your progress

5.1 a electron − + + − proton neutron nucleus
b i proton ii neutron iii electron iv nucleus
5.2 C
5.3 Pure diamonds are colourless and translucent, whereas those with other elements in them
are coloured.
5.4 A→2; B→5; C→4; D→3; E→1
5.5 a 10 °C b an ice age c 24 °C
5.6 When the ice was formed, bubbles of gas from the atmosphere were trapped in the ice.
These can be analysed. The deeper the ice that the gas came from, the older the sample.
Scientists can also tell from the way the ice was formed what the weather conditions were like
at that time. C
5.8
a false
b true
c true
d false
e true
5.9
a Any three from solar, wind, tidal, hydroelectric, biofuels.
b Global warming is the term used to describe the fact that the average global temperature of
the Earth is increasing. This effect is caused by an increase in the levels of gases, such as carbon
dioxide, methane and water vapour. These gases act like a blanket around the Earth, so that
less of the thermal energy generated on Earth is dissipated into the atmosphere.
c The carbon contained in fossil fuels has been locked up for millions of years. When we burn
them, this carbon combines with the oxygen in the atmosphere to produce more carbon
dioxide. The more carbon dioxide there is in the atmosphere, the greater the greenhouse
effect. The greater the greenhouse effect, the more the temperature rises, which adds to the
problem of global warming.
5.10 An analogy is the use of one structure, idea or process to explain another. Accept any
example from any discipline; such as the idea of the layer of greenhouse gases acting like a
blanket around the Earth.

Unit 5 Workbook answers.

Topic 5.1 The structure of the atom Exercise

5.1A Labelling the structure of the atom.

3 The following statements should be ticked

Electrons have less mass than protons.

Electrons have a negative electrical charge.

Neutrons have more mass than electrons.

Exercise 5.1B Models of the structure of the atom

2 In J. J. Thompson’s model, the particles he knew about, electrons and positively charged particles, are
scattered randomly throughout the atom and there is no nucleus. In Rutherford’s model, there is a
nucleus and the electrons are randomly scattered throughout the rest of the space in the atom.

3 Credit any of the scientists named, such as James Chadwick or Niels Bohr.

Exercise 5.1C Rutherford’s gold foil experiment

1 The diagram should be completed by drawing most particle pathways passing straight through the foil.
A few should be shown being reflected back or deflected from the gold foil.

2 The results of Rutherford’s experiment told him that the atom was mostly empty space, but with a
dense/solid nucleus.

Topic 5.2 Purity

Exercise 5.2 Purity

1 It means that all the atoms in the element are the same. So pure silver has only silver atoms.

2 Diamonds are made of carbon atoms. When diamonds are coloured, they have atoms of different
elements mixed in with the carbon atoms. When they have boron atoms the diamonds will be a blue
colour. If diamonds have nitrogen atoms mixed with the carbon atoms, the diamond will be a yellow
colour. The rarest colour of diamond is green. Green diamonds have nitrogen, nickel or hydrogen mixed
in with the carbon atoms.

3 92.5%

4 a 37.5%

b 91.7%

c 58.3%
6 Credit: a suitable scale on the horizontal axis; the points plotted accurately and neatly; a best-fit line
drawn.

7 The assistant gave an opinion. The science shows that 18 carat gold is much harder than pure gold.
Although the other samples are harder than pure gold, they are not harder than 18 carat gold, so it is
mostly not in line with the science.

8 The description should state that the hardness of the gold increases up to 18 carat gold and then
decreases at values greater than 18 carat.

9 This may be due to the fact that the other metal used in the alloys is not the same. Both silver or
copper can be used. The data do not say which is used in each case

Topic 5.3 Weather and climate

Exercise 5.3A

Words and meanings

temperature ➔ how hot it is

humidity ➔ how much water vapour there is in the atmosphere

precipitation ➔ rain, hail or snow which falls from clouds

visibility ➔ how far you can see; it depends on the atmospheric conditions or darkness

atmosphere ➔ the layer of gases around the Earth

meteorology ➔ the study of weather

Exercise 5.3B Weather or climate?

1 The weather is the atmospheric conditions over the short term, from minute to minute, hour to hour
or day to day. Climate is the average weather of an area over a much longer time, usually at least 30
years.

2 Credit approximate areas, such as Antarctica, northern Canada, Greenland and northern Russia, but
both Poles must be included and labelled.
3 The climate in the polar zone is very cold and dry all year.

4 Credit approximate areas, such as central America, south America (east of the Andes) central Africa,
south-east Asia, the north-east tip and south-east coastal strip of Australia, but tropical zone in more
than one continent must be shown and labelled.

5 The climate in the tropical zone is hot and wet all year. 6 Meteorologists record the weather in so
much detail because they are looking for patterns to see if they can predict what will happen in the
future. Knowing what the weather will be like has a big effect on the agriculture, transport, health and
other industries.

Exercise 5.3C Weather data

1 Data should be plotted as instructed with the date and time along the horizontal axis and the
temperature up the vertical axis. Credit a suitable scale, labelled axes, accurately plotted points and the
points joined ‘temperature style’, that is point-to-point.

2 It is difficult to see any pattern in these results but learners may spot that generally the temperature at
00:00 is lower than that for the rest of the day. The temperature often rises during the day and falls a
little over night. They should give examples. They may be able to link the small fall in temperature to the
fact that Iceland has a very long day length. If they fail to see a pattern, give them credit if they give
examples.

3 The only ‘pattern’ in the week is that the temperatures are fairly constant.

4 The temperature on this day remained constant from 06.00 to 18.00 and that was not typical of other
days during the week.

5 The description of this climate zone is cold and dry.

6 This week the weather in Iceland was not very cold and there was rain, which is not typical of this
climate zone.

7 Credit ideas about Iceland being an island in the middle of an ocean and a long way from any other
land. They may also realise or find out that the winds and weather systems move quickly in this area and
are influenced by the Gulf Stream.

Topic 5.4 Climate and ice ages

Exercise 5.4A Wordsearch
Exercise 5.4B Soil cores

1 a The oldest peat is from the bottom of the bog.

b The plant material has not rotted because the conditions in the bog slow down decay. There is not
enough oxygen and the conditions are acidic.

c Scientists hope to find out which plants were growing in that area thousands of years ago. If they can
identify the plants from their pollen, they can then work out what the climate was like at that time.

2 a These periods are the glacial periods.

b These periods are called interglacial periods.

Exercise 5.4C Climate cycles

1 The graph should be labelled with the peaks as interglacial periods and the troughs as glacial periods.

2 About 75000 years ago. It lasted from about 75000 years ago until about 25 000 years ago, so it lasted
about 50 000 years.

3 In an interglacial period the average temperatures are generally above freezing reaching as high as 20
°C.

4 When the temperatures are well below freezing for a long time, most living organisms cannot survive.

5 There have been four glacial and five interglacial periods over the past 450 000 years.

The first interglacial period was 85 000 years long and was followed by 25 000 years of a glacial period.

The second glacial period lasted 70 000 years the second interglacial period was warmer and lasted
longer than the first.
The third glacial period lasted 20 000 years so the glacial periods seem to be getting shorter. During the
third interglacial period (about 225 000 years ago) there was a short, sharp dip in the average
temperatures. The next glacial period was longer and the next interglacial period had very high average
temperatures, the highest of all the interglacial periods in this time span, and lasted until about 75 000
years ago. The most recent glacial period lasted about 50 000 years and we have been in the current
interglacial period for about 25 000 years.

6 The evidence we have comes from core soil samples from peat bogs and from the evidence in the
landscape from the effect of glaciers.

Topic 5.5 Atmosphere and climate

Exercise 5.5A

In the first billion years after the Earth formed there were lots of volcanoes. These produced gases,
which made up the atmosphere. The water vapour that was produced condensed, to form lakes and
oceans. The early atmosphere was mainly made up of carbon dioxide gas. There was little or no oxygen
gas. This is like the atmosphere of the planet Venus today. As plants began to grow on Earth, they used
up the carbon dioxide gas and produced food by the process of photosynthesis. Over billions of years
the carbon in the carbon dioxide gas became locked up as fossil fuels, such as oil and coal and as
carbonates in sedimentary rocks such as limestone. This caused the levels of carbon dioxide in the
atmosphere to fall.

Exercise 5.5B

1 80%

2 10%

3 0.038%

4 It decreased very quickly at the start and then continued to decrease, but at a much slower rate.

5 The level of carbon dioxide has increased quite dramatically over the past 200 years. This is because,
as industry developed, more fossil fuels were burnt to provide energy for factories and transport. More
forests have been cut down to use the wood and make room for people, crops and farm animals, so this
means less carbon dioxide from the atmosphere is being used up.

Exercise 5.5C

1 The answers will depend on what learners have found out, but as a minimum should include the
following: There is evidence that iron oxide was formed in rocks after the period 2.1 to 2.0 billion years
ago, not before. There is evidence from the pockets of air trapped in the ice cores from Greenland and
Antarctica. We have measurements of the percentage of gases in the atmosphere over the past 100 or
so years.

2 The answers will depend on what learners have found out, but as a minimum should include the
following: There is evidence from the ice cores about the way the ice was formed over time. There is
evidence of an increase in the rate at which the polar ice caps and glaciers are melting. There is evidence
of the sea levels increasing.
3 The evidence from a long time ago is not direct evidence, but has been inferred from other things,
whereas the records over the past 100 years were taken directly and there are lots of records. However,
even with the more recent records we cannot be sure of the way in which they were taken unless they
were taken and recorded by professionals that we can trust.