Essential natural science 1

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Contents
PAGE

1
2

About this book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

Learning to learn Getting closer to the stars! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

The Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

Planet Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Learning to learn All creatures great and small . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3
4
5
6
7

Living things . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Invertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Vertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
The plant and fungi kingdoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
The simplest living things . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Learning to learn Rock stars and instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

8 The Earth’s atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
9 The hydrosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
10 Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
11 Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Learning to learn It’s elementary! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

12
13
14

Matter and its properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Everything is matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Atoms and elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Vocabulary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Key language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

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Learning to learn

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A

B

ABOUT THIS BOOK
• Look at these illustrations.
Match them to the units
on the opposite page.
Then look at the book,
and check your answers.
Unit .........................

C

D

Unit .........................

F

E

Unit .........................

G

Unit .........................

I

Unit .........................

Unit .........................

Unit .........................

K

Unit .........................

M

Unit .........................

Unit .........................

H

J

L

Unit .........................

Unit .........................

N

Unit .........................

Unit .........................
3


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YOU ALREADY KNOW A LOT!
Work with a partner. Try to answer these questions.
THE UNIVERSE
How many planets in our galaxy can you name?

THE EARTH
How long does it take the Earth to rotate on its axis?
And how long does it take to orbit the Sun?

INVERTEBRATES
Can you name six invertebrates?

PLANTS
Plants are autotrophic: they make their own food.
What is the name of the process by which plants do this?
THE EARTH’S ATMOSPHERE
Can you name three meteorological instruments?
What does each one measure?

THE HYDROSPHERE
Water is present on Earth in gaseous, liquid and
solid form. Name four different places where you
can find water in nature.


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MINERALS
Quartz is a mineral. Can you name any other minerals?
Can you say what each is used for?

MATTER AND ITS PROPERTIES
Oil floats on water.
Which has the greatest density, oil or water?

THE STATES OF MATTER
Look at these three drawings.
They represent a solid, a liquid and a gas.
Can you match each drawing to its state?

1
UNIT

The Universe

What do you remember?
• What are the points of light in this photo?
• What is the difference between …
– a star and a planet?
– a moon and a comet?

STUDY A UNIT
Look at page 8, the first page of Unit 1

• What is the title of the unit?
• How many different sections are there on the page?
What are they about?

Key language

In this unit, you will …
• Learn about the characteristics of the
Universe
• Calculate astronomical sizes and distances
• Analyse the components of the Universe
• Compare sizes: the Sun and the planets
• Create a constellation poster

Describing
Planets are spherical bodies which orbit the Sun.
Asteroids are rocky objects which are irregular in shape.

Comparing
Dwarf planets are smaller than planets.
The Earth is larger than Mercury

Giving instructions
Study the constellations.
Research more about them on the Internet.

• What do you think you will learn about in Unit 1?
Now look at the rest of Unit 1

Content objectives

8

• How many sections are there in this unit?

• What can you find on page 17?
How is this useful?

• What are most of the illustrations about?

Symbols

• Some words are in bold. Why is this?

• The text is recorded on the CD.

• How many activities are there in this unit?

• The information you need is
available on the CD.

• What will you do in the Hands on section, page 15?

7


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Getting closer to the stars!
Telescopes are used to see objects that are too far away to be seen with the naked eye. They also provide a
closer view of distant things. Astronomers use large telescopes to study the planets, stars, and other objects
in space. Without telescopes, we wouldn’t know much about celestial bodies!

Lenses or mirrors?
Telescopes with lenses are called refracting telescopes.
Lenses bend the light.
The largest telescopes use mirrors instead of lenses
Telescopes with mirrors are called reflecting telescopes.
Mirrors reflect light.

Look through
this end. The
things you
observe seem
closer!
eyepiece: lens
to view the image
focus adjustment:
move this to make
the image clearer

Some telescopes are small enough to be carried in one hand.
Others can be huge, bowl-shaped radio telescopes, more than
300 metres in diameter. This is longer than three football pitches!

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Optical telescopes consist of a long tube, with one end narrower than
the other. They can “perceive” light, just like eyes.

tube

OOPS!
Wrong end!
objective lens: the
lens closest to the
object being viewed

How does a telescope work?
Objects reflect light. This light enters our eyes, and
we see the object. Optical telescopes have an
objective lens: a curved piece of glass at the wide
end. This lens bends the light from the object so
that it forms an image – a picture of the object –
inside the telescope. The light from this image then

goes through the eyepiece, at the narrow end of the
telescope. The eyepiece bends the light back again,
so the object looks big.

tripod: three-legged
stand to support the
telescope

The Gran Telescopio Canarias (GTC),
also called GranTeCan, is a 10.4 m
reflecting telescope, located on a volcanic
peak (2,400 metres) on the island of La
Palma, Spain.
It took seven years to construct!

Activities
1. Galileo Galilei invented the telescope. Why was this such an important
discovery? What did astronomers know about the stars before then?
2. Research. Have you heard of the Hubble telescope? When was it built?
Where is it? What pictures does it take?

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UNIT

1

The Universe

What do you remember?
• What are the points of light in this photo?
• What is the difference between …
– a star and a planet?
– a moon and a comet?

Content objectives

Key language

In this unit, you will …

Describing

• Learn about the characteristics of the
Universe

Planets are spherical bodies which orbit the Sun.
Asteroids are rocky objects which are irregular in shape.

• Calculate astronomical sizes and distances

Comparing

• Analyse the components of the Universe

Dwarf planets are smaller than planets.
The Earth is larger than Mercury.

• Compare sizes: the Sun and the planets
• Create a constellation poster

8

Giving instructions
Study the constellations.
Research more about them on the Internet.


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1. What is the Universe like?
Scientists developed two different theories to explain what
the Universe was like.

Activities

1. Find ten words in the word search.

M P
I

L A N E T S

G R

L A A S A

L U A T S R P T
K N E

• Geocentric theory
nd

2 century BC: Ptolomy
proposed that the Earth was
the centre of the Universe.
That is, the Sun, Moon and
planets orbited the Earth.

• Heliocentric theory
In 1542, Nicolas
Copernicus proposed
that the Sun was at the
centre of the Universe.

In 1610, Galileo Galilei invented the telescope, and proved the

Heliocentric theory: the planets and stars revolve around the Sun.

L

T T A E

Y S E N A H C

L

W O H B R X E

L

A T M S U N Y

I

Y M O O N L

G T

K E S W C P A E
2. Imagine an alien friend from
another galaxy wants to write to
you. Write your galactic address.

What makes up the Universe?
The Universe is all the matter, energy and space that exists.
The Universe is made up of galaxies which contain stars. Stars can have planetary systems

made up of planets and satellites. Galaxies are separated by vast spaces.

Galaxies are a vast collection of stars, dust and gases, held together by the
gravitational attraction between the components. They appear in groups called
galaxy clusters. Scientists think the vast spaces between the galaxies are empty.
Our galaxy, the Milky Way, belongs to the Local Group galaxy cluster.
Stars form when clouds of gases are pulled together by gravitational forces. They
are so hot inside that they emit heat and light. A galaxy can have up to five hundred
thousand million stars. An enormous cloud of gas and dust, a nebula, surrounds
the stars.
Planets are bodies which orbit some stars. They do not emit light; they receive light
from the star. They make up planetary systems. Our planetary system is the Solar
System. It is made up of eight planets and one star, the Sun, as well as moons,
comets and asteroids. The Solar System is located on a spiral arm of the Milky Way.
Natural satellites orbit some planets. The Earth’s natural satellite is the Moon.

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2. How big is the Universe?
The Earth seems huge, but, in reality, it is small
compared to the Sun. The Sun is only one

of the millions of stars in the Milky Way.
To imagine the size of the Universe,
use these comparisons with everyday objects.

Activities
3. Express the distance of Mercury, Mars and Pluto
from the Sun in kilometres.

• Imagine the Sun is the size of a pea.
• The closest star is another pea, five hundred
and forty kilometres away from the first pea.
• The Earth is like a particle of dust situated
two metres away from the first pea.
• The Milky Way contains one hundred thousand
million peas which form a circle with a radius
of seven million kilometres.
What units of measurement
do astronomers use?

Mars

Mercury

Pluto

4. Research the term light-year. Why is it used in
astronomy?

Did you know that...?

• Astronomical unit (AU). This is the distance
from the Earth to the Sun. Approximately
150 million kilometres. Compare the distance
of these planets from the Sun:
– Mercury: 0.4 AU
– Mars: 1.5 AU
– Pluto: 39.4 AU
• Light-year. This is the distance light travels in
one year. Light travels 300,000 km
in one second or
9.5 trillion km
in one year.

10

Source of light

Time to reach
the Earth

the Sun

8 mins. 20 sec

Centauri, the
nearest star

4 light-years

Betelgeuse

500 light-years

The radius of the Sun is 109 times
greater than the radius of the Earth.


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3. What makes up the Solar System?
The Solar System was formed approximately
five thousand million years ago from the gas and
dust of a nebula.
Our Solar System is made up of the Sun, eight
planets with their satellites, dwarf planets and
small solar system bodies. The Sun is the central
body.
• The Sun consists mainly of two gases:
hydrogen and helium. It is the closest star
to Earth.
• Planets are spherical bodies which revolve
around the Sun. They all move in elliptical
orbits, held by the gravitational force of the
Sun. Planets are much larger than other

celestial bodies which orbit the Sun.
Mercury, Venus, Earth and Mars are made up
mainly of rock. Jupiter, Saturn, Uranus and
Neptune are made up mainly of gases.

The planets in the Solar System
Planet

Distance from
Sun (AU)

Period of
rotation

Period of
revolution

Mercury

0.39

58.65 days

88 days

Venus

0.72

243 days

224.6 days

Earth

1.00

23 h 56 mins

365.25 days

Mars

1.52

24 h 37 mins

1.88 years

Jupiter

5.20

9 h 55 mins

11.86 years

Saturn

9.54

10 h 40 mins

29.46 years

Uranus

19.19

17 h 14 mins

84.07 years

Neptune

30.06

16 h 7 mins

164.82 years

Activities
5. Which planet …
•
•
•
•

• Dwarf planets are spherical bodies which orbit
the Sun. They are smaller than planets.

• Small solar system bodies are other celestial
bodies which orbit the Sun. They include
asteroids, comets and satellites. Satellites
orbit planets and consist of rock.

takes the longest to orbit the Sun?
is the fastest to orbit the sun?
has the longest days?
has the shortest days?

6. Why is a “day” on Venus longer than its “year”?
7. What is an orbit?
8. What do you call the imaginary plane of the
Earth’s orbit?

How do the planets move?
Celestial bodies like the Earth, have two types of movement:
Rotation. Celestial bodies spin or rotate
on an invisible axis. This invisible line is
called the rotational axis.

Revolution. Celestial
bodies revolve around
other celestial bodies.

Orbit. A curved path which
a celestial body follows in its
revolution around another celestial
body. The orbit of the Earth
around the Sun is an ellipse.

ecliptic plane

rotational axis of
the Moon
rotational axis

terre
strial
orbit

lunar orbit

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Mercury
Diameter: 4,880 km

Venus
Diameter: 12,104 km

Earth
Diameter: 12,740 km

Mars
Diameter: 6,794 km

4. Which are the inner planets?
The inner planets are the four planets closest to the Sun: Mercury, Venus, the Earth and Mars.

The Earth is the only planet that has life on it. The other
planets are too hot or too cold.

In 2004, the robots Spirit and Opportunity landed on
Mars. They investigated the possible existence of water.
INNER PLANETS

Did you know that...?
Pluto, Ceres and Eris are
dwarf planets. Pluto used to
be considered a planet. In
2006, the International Union
of Astronomers reclassified it
as a dwarf planet.

Terrestrial or rocky planets: the crust and mantle are
made of rock. The core is metallic
Mercury

Venus

Earth

Mars

Diameter (Earth = 1)

0.382

0.949

1

0.532

Diameter (km)

4,880

12,104

12,740

6,794

Ϫ180 to 430 ºC

465 ºC

Ϫ89 to 58 ºC

Ϫ82 to 0 ºC

none

CO2

N2+O2

CO2

0

0

1

2

no

no

no

no

the smallest
and closest to
the Sun

rotates in
opposite
direction

the only
planet
with life

very thin
atmosphere

Average surface
temperature (ºC)
Atmosphere
Satellites
Rings
Interesting
characteristics

Ceres

CO2 ϭ carbon dioxide

12

N2 ϩ O2 = nitrogenϩ oxygen


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Uranus
Diameter: 51,118 km

Saturn
Diameter: 120,536 km

Jupiter
Diameter: 142,984 km

5. Which are the outer planets?
Jupiter, Saturn, Uranus and Neptune are the four outer planets.
They are called gas giants because they consist mainly of gases.

Neptune
Diameter: 49,492 km

Saturn’s rings are made up of small particles, mostly ice.

OUTER PLANETS

Activities

Gas giants: they consist mainly of gases

9. Which planet …
Jupiter

Saturn

Uranus

Neptune

11.209

9.44

4.007

3.883

142,984

120,536

51,118

49,492

Ϫ150 ºC

Ϫ170 ºC

Ϫ200 ºC

Ϫ210 ºC

H2ϩHe

H2ϩHe

H2ϩHe

H2ϩHe

63

59

27

13

yes

yes

yes

yes

largest planet,
most satellites

system of rings

rotational axis is
almost horizontal

greatest distance
from the Sun

• has the most satellites?
• is closest to the Sun?
• supports life?

H2 ϭ hydrogen

• is the largest in the
Solar System?
• spins on its axis in the
opposite direction?
10. If you live on Venus, will
the Sun rise in the East
and set in the West?

He ϭ helium

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Pluto
Mercury

Mars

Earth
comet

Neptune

Saturn
Jupiter

Venus
Uranus
Asteroid belt

The Solar System. Observe the elliptic paths of the planets’ orbits around the Sun. Notice that the orbit of Pluto, a dwarf planet,
is more inclined.

6. What are small Solar System bodies?
There are two main types: asteroids and comets. They orbit the Sun.
• Asteroids are rocky objects which are irregular in shape. They can
be several hundred kilometres in diameter, but most are only
a few metres wide. Asteroids orbit around the Sun. Most of them

are between the orbits of Mars and Jupiter. This area is called
the asteroid belt.
• Comets are small bodies that travel around the Sun in highly
elliptical orbits. They are irregular in shape. The nucleus is made
up of a mass of ice, dust and gas. When comets travel close
to the Sun, some of the ice evaporates, creating the long,
bright tails of the comets.

Activities
11. Compare the main characteristics of the inner and outer planets.
12. Describe an inner or outer planet. Your partner will identify it.

14

This inner planet
This outer planet

is smaller / larger than
is the largest / smallest.
has (no)

the Earth.
… satellites.

The atmosphere

is made up of

carbon dioxide.
helium.

…

Halley’s comet has a bright tail. It was
named after the English scientist
Edmund Halley. He was the first
scientist to calculate the orbit of this
comet. Halley’s comet will next be
visible from Earth in 2061.


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Hands on
Prepare a constellation poster
Constellations are imaginary patterns of bright stars.
All societies have invented constellations. The
Ancient Greeks invented the constellations we call
the twelve signs of the zodiac.
There are 88 official constellations. However, most
of them do not really look like the mythical figures
they represent.
The night sky looks different in the Northern and
Southern Hemispheres. The position of the
constellations changes with the seasons because

of the movement of the Earth.

Cassiopeia

Orion

Ursa major

Gemini

1. Study these constellations. Which ones can you
see in the night sky where you live?

The constellation Orion

2. Choose one of the constellations and make a
poster.
a. Find more information in encyclopedias or on
the Internet.
b. Draw the constellation, or cut out a drawing
or a photo of it.
c. Write some sentences about the constellation.

Orion represents the hunter.
The three stars in the middle are his belt.
His sword hangs from his belt.
You can see his sword and his bow.

Activities
13. Look up the constellation for your sign

of the zodiac.

14. Choose another constellation.
Research more about it on the Internet.

a. Find out where and when it is most clearly
visible in the sky. Is it in the Northern or the
Southern Hemisphere?
b. Write the dates associated with this sign.

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Activities
21. Talk about astronomical distances with a partner.

15. Label each diagram with the name of …

How far away is … from …?
It is … km / … light-years away.

a. a theory of the universe

b. the person who proposed the theory.
b

a

Astronomic distances from the Earth
Object

16. Make a drawing of the Solar System and label it: the
Sun, the inner planets, the outer planets, Pluto and
the asteroid belt.
17. Make a timetable of your daily activities on these
planets. Give an approximate duration for each.
• Earth. Rotation: 24 hours
• Mercury. Rotation: 58.65 Earth days
• Jupiter. Rotation: 9.841 Earth hours

Distance

space station

300 km

weather satellite

36,000 km

the Moon

384,000 km

the Sun

150,000,000 km

Pluto

6,000,000,000 km

Alpha Centauri

4 light-years

22. Research the latest astronomic discoveries. Report
your findings to the class.
23. This drawing shows the positions of a comet
in orbit.
When a comet gets close to the Sun, why does it
develop a tail? Why does an asteroid not?

Duration on …
Activities

Earth

Mercury

Jupiter

18. What two types of movement do all planets have?

Describe them.
19. Describe the composition, temperature and
movement of the Sun.
20. Make an illustrated list of the planets. Write them in
order: start with the closest one to the Sun.
a

b

c

24. Draw a diagram of the Solar System seen from
above. Include the rotation and revolution
movements of each planet.
25. Copy and complete to situate the Moon in the
Universe:
The Moon is a satellite of … which belongs to the
planetary system called … . The star of this planetary
systems is … . It belongs to a galaxy called … .
This galaxy is part of the galaxy cluster called … .

d
e
f

16

g

h

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THE UNIVERSE

What should you know?

1

Early
concepts

• Geocentric theory: the Earth is the centre of the
Universe. The Sun, Moon, stars and planets revolve
around the Earth.
• Heliocentric theory: the Sun is the centre of the
Universe. The Earth, planets and stars revolve
around the Sun.

Components

• Galaxies are grouped together in galaxy clusters.
• Galaxies contain thousands of millions of stars.

• Stars are massive spherical bodies of gases. Some
stars have planetary systems with planets,
satellites, asteroids and comets.

Units of
measurement

• Astronomical unit (AU): the distance between the Earth and the Sun, about
150 million kilometres.
• Light-year. The distance that light travels in one year: about 9.5 trillion kilometres.

The Solar
System

The Solar System is the planetary system of our Sun.
It consists of:
• The Sun: a medium-sized star in the Milky Way galaxy.
• Planets:
Inner: Mercury, Venus, Earth and Mars.
All are rocky.
Outer: Jupiter, Saturn, Uranus, and Neptune. All are gaseous.
• Dwarf planets: Pluto, Ceres, Eris
• Natural satellites: celestial bodies which revolve around planets and dwarf planets.
• Small Solar System bodies
Asteroids: small rocky bodies which orbit the Sun. Some form belts. The asteroid
belt: a band of asteroids between the orbits of Mars and Jupiter. Comets: masses of
ice and rock found beyond the orbit of Pluto.

Projects
INVESTIGATE: Could Mars support life?

First, list the factors that make life possible on Earth.
Then, investigate this website: http//solarsystem.nasa.gov/planets/profile.cfm?Object=Mars
WEB TASK: Do you want to visit Mercury, Jupiter or Mars?

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UNIT

2

Planet Earth

What do you remember?
• In this photo, what does each colour correspond to?
• Is the Earth an outer or an inner planet?
• What is the interior of the Earth like?
• Where does life exist on Earth: in the geosphere or the biosphere?

Content objectives

Key language

In this unit you will …

Describing

• Learn about the Earth’s characteristics

Water exists in three states.
It takes 28 days to orbit the Earth.

• Identify lunar phases
• Describe the geosphere
• Learn about the Earth’s “spheres”
• Reproduce conditions of solar and lunar
eclipses

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Expressing cause and result
This causes the sequence of day and night.
This makes the seasons occur.

Comparing
The days get shorter.
Ocean trenches are the deepest areas.


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1. What is the Earth like?
The Earth is special for many reasons. The Earth is
the only planet with:
• an atmosphere containing oxygen

1. Draw a diagram of the Earth, as seen from
space. Draw two people: one at the North Pole
and one at the South Pole.

• an average temperature of 15ºC
• a water cycle
• life as we know it
All these characteristics make the Earth a unique
planet in the Solar System.
• The atmosphere consists of a mixture of gases.
Nitrogen and oxygen are the most abundant.
Oxygen is essential for plant and animal
respiration. There is also carbon dioxide,
essential for photosynthesis.
• The average temperature is 15°C on the
Earth’s surface. This is possible because of the
distance from the Sun and the composition of
the atmosphere.
• Water exists in three states (ice, liquid, water

vapour) due to temperature variations. These
variations make the water cycle possible.

Photo of the Earth and the Moon taken by satellite.

Activities

2. Find out the mixture of gases and the average
temperatures of Venus and Mars. Why do you
think life is only possible on Earth?

• The Earth has a relatively large natural
satellite, the Moon. The gravitational attraction
of the Moon causes ocean tides.
• The Earth’s magnetic field protects living
beings from dangerous solar radiations.
• Conditions exist for life. Thousands of millions
of years of evolution have produced the variety
of species there are today. This includes
humans.
• There is considerable geological activity on the
Earth: earthquakes, volcanoes, mountain
building, erosion, etc.

Volcanoes are proof of intense geological activity.

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2. How does the Earth move?
direction of rotation

The Earth moves in two different ways:
Equator

• Rotation: The Earth rotates on a slightly tilted
axis, always in the same direction. This
rotation causes the sequence of day and night.

North Pole
plane
of the Earth’s
orbit

Sun’s rays

• Revolution: The Earth’s revolution around the
Sun is an ellipse. It takes 365 1⁄4 days to
complete the revolution. This is one year.

Northern
Hemisphere

Summer
Solar rays strike perpendicular to the Earth’s
surface and produce more heat.

D

ay

rotational axis
23.5°

ht
Nig
South Pole
Southern
Hemisphere

The rotation of the Earth. It is day on the half of the Earth facing
the Sun. It is night on the half facing away from the Sun.

What causes the seasons on Earth?
Winter

Two factors combine to cause the seasons:
• the revolution of the Earth around the Sun
• the Earth’s axis is tilted at an angle of about 23.5º

Solar rays strike the Earth at a
steeper angle and produce less heat.

The tilt of the axis causes differences in temperature
and in the duration of day and night.
The Sun’s rays strike the Earth in different ways
depending on the seasons.
The tilt of the axis makes the seasons occur at
different times of the year in the Northern and
Southern Hemispheres.
Spring. The days get longer and the
nights get shorter until 21st June the longest day.

Spring equinox
21st March

Winter. The days get longer and the
nights get shorter. On 21st March,
day and night are the same length.

Winter
solstice
21st December

Summer
solstice
21st June

Summer. The days get shorter and the
nights get longer. On 22nd September
day and night are the same length.

Autumn
equinox
22nd September

Autumn. The days get shorter
and the nights get longer until 22nd
December- the shortest day.

The seasons in the Northern Hemisphere

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3. How does the Moon move?
The Moon moves in two different ways:

1

• Rotation. The Moon takes 29.5 days to
rotate once on its axis: a “lunar day”.

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• Revolution. The Moon takes about
twenty-eight days (twenty-seven days
and eight hours) to orbit the Earth once.

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3

A “lunar month” is the period of time
between two new moons. It is about 29.5 days.
A “lunar day” is as long as a “lunar month”.
As a result, the same side of the Moon always
faces the Earth.

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4
5
The same side of the Moon always faces the Earth. The red dot
indicates the dark or hidden side. It is never visible from Earth.

Activities
3. Draw a diagram to show the phase of the
Moon in the Northern Hemisphere today.
4. When is there a New Moon?
5. Draw a diagram of the phases of the
Moon in the Southern Hemisphere.

The phases of the Moon
New Moon

Last Quarter

The Moon is between the Sun and the
Earth, so the Moon is not visible.
The dark side (not illuminated) faces the
Earth. The Moon rises and sets with the
Sun, but you cannot see it from Earth.

Half the side is lit by the Sun. The
illuminated part slowly shrinks. It rises
at midnight and sets at noon.

First Quarter

Full Moon

Half the side is lit by the Sun.
The illuminated part slowly increases.
It rises at noon
and sets at midnight.

When the Earth is between the Moon
and the Sun, the entire Moon is visible.
The illuminated side faces the Earth.
It rises and sets with the Sun.

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Hands on
Reproducing eclipses
If the Moon passes between the Sun and the Earth, and blocks
off the sunlight, a solar eclipse occurs.
If the Moon passes behind the Earth, so the Earth prevents sunlight
from reaching the Moon, a lunar eclipse occurs.

Materials

the Sun

the Moon
the Earth

1. Reproduce a solar eclipse. Position the planets: the Moon should block the Sun’s light
and project a shadow on the Earth.

2. Reproduce a lunar eclipse. Position the planets: the Earth should block the Sun’s
light and project a shadow on the Moon. Remember: a lunar eclipse can only take place
during a full moon.

3. In your notebooks, copy the diagrams for both eclipses.
umbra

penumbra

penumbra

Earth

Moon

Sun

Sun

Moon

Earth

Solar eclipse

Activities
6. Find out when the next solar and lunar eclipses will
take place.
Visit this site:
/>7. How must you protect your eyes when observing a
solar eclipse?

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umbra

Lunar eclipse


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4. How many “spheres” make up the Earth?
The Earth is the only known planet which contains water and living things.
It is made up of four interrelated parts or “spheres”. These are:
• The geosphere. The solid part which includes
the crust, mantle and core. The upper 100 km
of the geosphere is called the lithosphere:
it is the most rigid part.
• The atmosphere. The air: a layer of gases which
envelops the Earth.

• The hydrosphere. All the water on the Earth.
• The biosphere. All the living things which
inhabit the Earth.

The geosphere
The geosphere consists of three concentric layers: the crust,

mantle and core. The crust and the upper mantle make up
the lithosphere.
The crust is the outer layer of
rock. The most abundant
minerals are silicates.
• The continental crust
makes up the
continents. Granite
is the most
common rock.
• The oceanic
crust makes up
the ocean floor.
It was created
by intense
volcanic activity
at mid-oceanic
ridges. Basalt, a
volcanic rock, is the
most common rock.

mantle
outer
core
(liquid)
inner
core
(solid)

The mantle is the middle layer,

below the crust. It lies
2,900 km below the
surface. It is made up
of mostly solid rock
material. The
temperature is
higher here, from
1,000ºC to
4,000ºC, so
some areas are
melted rock.
The core is the
centre of the
Earth, below the
mantle. It is made
up mainly of iron.
The temperature is
over 4,000°C. The outer
core is liquid. The inner
core is solid.

Activity

continental crust
(thickness varies from 7 to 70 km)

oceanic crust
(thickness varies
from 7 to 10 km)

8. Show the three layers of the
geosphere in a diagram. Label each
layer: main components,
temperature and state: solid or liquid.
Label the two types of crust.

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5. What is the surface of the Earth like?
From outer space, the Earth looks blue because of
the vast expanses of water on its surface.
The distribution of materials that make up the
Earth’s crust form the different types of land relief.

Ocean floor relief features
• The average depth is 4,500 m.
• The main relief features are:
– Oceanic (mid-oceanic) ridges. Chains
of submarine mountains with intense
volcanic activity. Example: the Mid-Atlantic
ridge.

– Oceanic trenches. The deepest areas
of the ocean. Example: Mariana Trench:
11,034 m deep.
– Abyssal plains. The largest plains on the
planet: 4,000 or 4,500 m deep.
– Submarine volcanoes may create volcanic
archipelagos. Examples: the Canary Islands,
the islands of Hawaii.

Continental relief features
• The average altitude is 600 m.
• The three main relief features are:
– Mountain ranges. Chains of high mountains.
Examples: the Himalayas in Asia or the Andes
in South America.
– Great plains. Large extensions of flat land.
Examples: the Amazon plain in South
America or the Sahara desert in Africa.
– Continental shelves. The areas near the
coastline, under the sea, that are made of
continental crust, not oceanic crust. These
areas slope down from the coastline to a few
kilometres out to sea, to a depth of about
200 metres.

Oceanic relief forms can rise up to 2 km
from the ocean floor. In some places they
appear above the water to form islands.
Example: Iceland.

Cross-section of the Earth’s surface

mountain range

continental great plain

submarine volcano
mid-oceanic ridge

continental shelf

abyss

abyssal plain

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oceanic trench


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6. What are the other three Earth “spheres”?
Apart from the geosphere, the other three Earth “spheres”

or systems are the atmosphere, the hydrosphere and the
biosphere.
The atmosphere
The atmosphere is the layer of air which surrounds the Earth.
Air is a mixture of gases. The main components are: nitrogen
(78 %) and oxygen (21 %). Oxygen is one of the necessary
conditions for life. There are also small quantities of carbon
dioxide (CO2) and other gases.

Activities
9. Say a relief feature. Your partner
says if it is continental or ocean
floor.
10. Which continental feature is under
the sea?
11. Describe the four different spheres
that make up the Earth. List
examples of features in each
sphere.

The hydrosphere
The hydrosphere is all the water on, under and above
the Earth.
The hydrosphere is made up almost exclusively of liquid
water, but also snow and ice. Other materials in the
hydrosphere are the mineral salts in water. Sea water is very
rich in mineral salts, but fresh water has few salts.
The biosphere
The biosphere includes all the living things which inhabit
the Earth. Living things influence the physical and chemical

changes in the Earth. For example:
• In the Earth’s crust: Animals live in the ground and plants
take mineral salts from the soil. Plant roots can break up
rocks.
• In the atmosphere: Microorganisms which live in the soil
produce nitrogen. Oxygen is produced during
photosynthesis by plants, algae and some bacteria. Many
living things cause evaporation.
• In the hydrosphere: Living things contain water. Plants
take water from the ground. Many organisms live in aquatic
environments.

Did you know that...?
The water cycle refers to how water
evaporates, rises, condenses, falls
to the Earth as rain or snow and
moves around.
This cycle was described 2,500 years
ago byThales.

Coral produces
exoskeletons which
accumulate to form a
rocky shelf.
This atolon in Tahiti is
made up of living
things.

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