Focus On Science by Top That Publishing Ltd

UNDS

TRY S I EM H C

T EN EM L FE

STUD

Y OF

PHYMASTTIERCAS N

Y OF ALL LIVING THINGS

SCIENCE

D N AN STUDY THROUGH OBSERVATIO

T EN IM R E EXP

ST UD

BIOLOGY

D ENER GY

DY TU

O MPO ND C SA

Science

CONTENTS What a Scientist Does Pages 4–5

Biology Pages 6–8

Sound Pages 11–13

Acids and Alkalis Pages 14–16

Crystals Pages 23–25

Electricity Pages 26-30

Microscope Pages 9–10

Solids, Liquids and Gases Pages 17–19

Static Electricity Pages 20–22

Principles of Flight Pages 31-32

CONTENTS Forces and Motion Pages 33–34

Gravity and Circular Motion Pages 43–46

Light and Photography Pages 54–57

Magnetism Pages 35–39

Fluids and Forces Pages 47–49

Elements and Compounds Pages 58–59

Bacteria Pages 40–42

Heat and Temperature Pages 50–53

WHAT A SCIENTIST DOES Science is about finding out what things are made of and how things work. Scientists do experiments to try to find out about the world we live in. Some scientists do their experiments in universities, while others work in hospitals. Wherever scientists work, they always make sure that they carry out their experiments as safely and carefully as possible.

What do scientists find out Scientists are very curious people. They test their ideas by doing experiments, which help find the answers to lots of questions. Scientists like to find out: • how something works; • why it does what it does; • where it comes from; • what it is made of.

Are scientists observant When scientists carry out experiments, they watch very closely and write down everything that they see. If they discover something new, they tell other scientists what they have found. By sharing their information and working together, they are more likely to make an important discovery.

Are science experiments dangerous Before you start to do any science experiments, you need to make sure you are prepared and safe. Investigating science is fun, but it can be dangerous, so sensible scientists follow strict safety rules. Ask an adult to help you carry out the experiments, while you watch carefully and make notes – just like a real scientist!

Advice for Supervising Adults • All of the experiments in this book need the help and supervision of a responsible adult. • Read and carefully follow the safety advice and experiment instructions before carrying out any of the experiments in this book. • The experiments should be carried out on a firm and steady surface and the surrounding area should be kept clear of any obstructions. • Clothes should be protected and the work surface covered. • Wash hands before and after carrying out the experiments. • Clean all equipment after use. • Do not use electrical equipment with wet hands. • Plants, fruit and certain chemicals are used in the experiments in this book. If anyone who comes into contact with these substances is, or may be, allergic to them, do not carry out the experiment.

BIOLOGY Biology is the study of all living things, from the tiniest plants that can only be seen with a microscope to the world’s largest animals. There are millions of different plants and animals. Scientists study them to find out how they are made and how they live together.

Photosynthesis experiment Step 1 Ask an adult to cut the paper into small pieces. Stick a few pieces to the plant’s leaves.

Carbon dioxide and sunlight

You will need: • paper • scissors • a plant with large leaves • sticky tape

Oxygen

Step 2 Leave the plant in a light place for a few days. Remember to water it! Step 3 After a few days, take off the pieces of paper. The leaves will look dead where the pieces of paper were stuck. This shows how plants need light to grow. They convert energy from the Sun into food by a process called photosynthesis.

Water, nitrates and minerals from soil

The process of photosynthesis.

How to grow your own plant Step 1 Roll up the piece of blotting paper and place it in the container. Push the bean about halfway down between the paper and the container.

What are cells

You will need: • blotting paper • a plastic containe r • a broad bean seed • water

All living things are made of cells, whether they are plants or animals. Cells are like tiny factories where chemical reactions take place. These reactions, such as turning food into energy, help to keep plants and animals alive. Some cells work together in groups to do special jobs. These cells form tissue and organs that help living things grow, breathe, move, feed and reproduce.

Step 2 Fill the container with water until the paper is soaking wet. Place the container in a warm, dark place – an airing cupboard is ideal. Check it every day and add water if it looks dry.

Cells

Step 3 After a few days, a root will begin to form. A few days later, you should see a shoot. Move the container to a well-lit area to let the plant continue to grow.

DNA double helix

This experiment shows that plants need water, warmth and light to grow. Plants also get nutrients from the ground to continue their growth.

Each cell carries a code, which is held in a molecule called DNA, that gives the animal or plant its unique characteristics.

Who discovered genetics

What is DNA

Genetics – the study of how the characteristics of living things are passed on – was begun by an Austrian monk called Gregor Mendel. He bred pea plants and found that the size and colour of the pods was passed on through the generations.

Every animal and plant cell has a nucleus. The nucleus carries a chemical code that gives the animal or plant its unique characteristics. This code is held in a spiral-shaped molecule called deoxyribonucleic acid, better known as DNA. Each strand of DNA contains many separate instructions, called genes, and each gene controls a different characteristic – eye colour, for example.

DNA

Who discovered DNA The double helix (spiral) shape of the DNA molecule was discovered by James Watson and Francis Crick in 1953. It was one of the most significant discoveries of the twentieth century and the pair received numerous prizes and awards for their work.

Who discovered cells The idea that all living things are made of cells was first suggested by Theodor Schwann and Jacob Schleiden in 1838. They were right – the human body contains around 50 billion cells!

Human DNA is incredibly complex. Each DNA molecule will contain between 50,000 and 100,000 genes.

MICROSCOPE A microscope is one of the most important instruments used by scientists. It is used to make things bigger so that they can be seen in greater detail.

Eyepiece

This is the part that scientists look through. The eyepiece contains its own lens.

What are the parts of a microscope

Objective lenses

A microscope has objective lenses that magnify by different amounts. Each objective lens combines with the eyepiece to magnify the object thousands of times its normal size.

Body tube

This adjustable tube holds the eyepiece and the nosepiece.

Focusing knob

This is turned to bring the image into focus.

Stage Clips

These hold the slide in place.

Nosepiece

This holds one of the objective lenses.

Mirror

The mirror is used to reflect light through the stage onto the object.

Stage

This is where the object to be examined is placed.

What was an early microscope like

How powerful is a microscope Most optical microscopes magnify things between 50 and 1,000 times. The most powerful have up to 2,000 times magnification. Microscopes are used to find the causes of diseases, look at animal and plant cells, solve crimes, study rocks and metals, and much more! Some scientists use very powerful microscopes called electron microscopes. Electron A nettle leaf as microscopes can magnify seen through a powerful microscope. objects over 200,000 times!

Antoni van Leeuwenhoek invented a basic microscope in the 17th century. It was little more than a powerful lens mounted on a metal plate, but it made it possible to study things in great detail. The first microscopes were very basic.

What are compound microscopes Compound microscopes use multiple lenses. The compound microscope was invented in about 1590 by Zacharias Janssen. However, it was Robert Hooke who pioneered its use. He improved the original version and published a book called Micrographia in 1665.

Has microscope technology been used in other ways In 1609, Italian astronomer Galileo Galilei heard about Janssen’s work and found out how to use lenses to make a telescope. He was the first person to look at the Moon through a telescope.

FACT BYTES Search around your house for things to look at through a microscope: Feathers – you can zoom in to see the barbs. Paper – tear a piece of paper to see the fibres that

it is made of. Insects – creepy-crawlies are fascinating to look at

with a microscope.

Galileo Galilei.

SOUND A sound is made when an object vibrates – when it moves back and forth really quickly. This makes a wave, which we hear as sound. A sound can be very low, like a growl, or very high, like a scream.

You will need: • two plastic cups or yoghurt pots • a sharp knife • a length of string (about 6 ft)

How to make a cup phone

Step 1 Ask an adult to make a small hole in the middle of the base of each cup.

Step 2 Thread the string through the hole of one cup and tie a knot as shown. Do the same with the other cup.

The sound of your friend’s voice makes their cup vibrate. The vibrations travel along the string to your cup. The sound is reproduced by your cup vibrating.

Step 3 Hold one cup and ask a friend to take the other. Pull the string tight. Ask your friend to speak into their cup while you put your ear to yours. You will be able to hear their voice.

How do we hear

Can you feel sound waves

Our ears are designed to direct sound waves to our eardrums. Our eardrums vibrate, and the vibrations are passed through some tiny bones to a tube called the cochlea. Then the vibrations move special hairs that are connected to nerves. The nerves send signals to the brain, which are translated into sounds that we recognise.

Yes! Turn up the volume on a music system and hold your hand in front of one of the speakers. Only try this with your hand and NEVER your ear or you may damage your hearing. You should be able to feel the sound waves moving the air against your hand.

Human ears are designed to direct sound waves to our eardrums.

Pinna (the outer ear)

Semi-circular canals â&#x20AC;&#x201C; the fluid in these aids balance

Malleus

Cochlear nerve

Eardrum

Endolymph (the fluid that vibrates)

Incus

Cochlea Stapes Eustachian tube

To purchase this book and others in the series, vistit www.topthatpublishing.com.

What does a scientist do? How do we hear? What is lightning? How do aeroplanes fly? Bursting with bite-sized facts, illustrations and diagrams, this engaging 64-page book contains answers to all the questions you always wanted to ask about science – and more! No question is too tough, no answer too difficult to explain – Focus On titles are the ultimate in addictive reading!

Published by Top That! Publishing plc Copyright © 2010 Top That! Publishing plc Tide Mill Way, Woodbridge, Suffolk, IP12 1AP, UK www.topthatpublishing.com Top That! is a registered trademark of Top That! Publishing plc All rights reserved. 0246897531 Printed and bound in China