essa study guide

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Year 8 ScienceESSA Study guideCherine Spirou


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BODY SYSTEMS

Cells To Organ Systems

Cellsare the smallest unit of living things.

Tissuesare made of the same types of cells. Muscle tissue is made of muscle cells.

Organsare made of different types of tissues. The stomach is an organ made of glandular

tissue that produces chemicals to digest the food, muscle tissue to churn the food and

connective tissue to hold the other tissues together.

Organ systemsare made of different types of organs. The digestive system is made of

several organs including the mouth, oesophagus, stomach and intestine.

Multicellular organisms contain many cells that are specialised for particular roles. They are

organised together in organs and systems which all work together to keep the organism

alive.

Digestive System

The digestive system digests food for the body. It is made of several parts.

Mouthchews, moistens and swallows the food.

Oesophagustransfers the food from the mouth to the stomach

Stomachdigestion of the food continues here

Small Intestinedigestion of the food finishes and then the digested food is absorbed

into the bloodstream to be taken to al parts of the body

Large Intestineexcess water is reabsorbed into bloodstream and undigested food is

formed into faeces

Rectumthe faeces are stored here until they are removed through the anus.


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Circulatory System

The circulatory system transports blood around the body. It is made of several parts.

Heartpumps blood out into the blood vessels. It has four chambersthe left atrium,

left ventricle, right atrium and right ventricle. The diagram below shows the four

chambers and the direction of blood flow through them.

Blood vesselscarry blood to all parts of the body and then back to the heart. Arteries

carry blood away from the heart. They have thick, muscular walls because blood flows

through them under pressure.

Veinscarry blood back to the heart. They have thinner walls than arteries because the

blood is flowing through them without pressure but they have valves to stop the blood

flowing backwards.

Capillariesconnect arteries to veins. They deliver food and oxygen to cells and take

away carbon dioxide and other wastes. Their walls are one cell thick so that materialscan pass between them and the cells. Blood travels to the lungs to drop off carbon

dioxide and pick up oxygen. It then travels to all parts of the body to deliver the oxygen

and collect carbon dioxide.

Bloodis made of red blood cells that carry oxygen, white blood cells that fight

infection and platelets that help blood to clot.


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The Respiratory System

The respiratory system delivers oxygen to the blood and collects carbon dioxide from it. It is

made of several parts.

Tracheaalso called the windpipe, takes in air from the mouth and nose.

Bronchithe trachea branches into two tubes called the bronchi that enter the lungs.There they branch into smaller and smaller tubes.

Alveolialso called the air sacs, are at the end of the small tubes. They are surrounded

by capillaries. Oxygen passes from the alveoli into the blood in the capillaries and

carbon dioxide passes from the blood in the capillaries into the alveoli.

The Excretory System

The excretory system removes wastes from the body. Excretion is carried out by the

Lungswhich remove carbon dioxide and water vapour when we breathe out

Skinwhich removes salts and water in sweat

Kidney systemwhich removes urine; It is made of several parts.

Kidneysfilter urea and excess salts from the blood and mix them with water to form

urine.

Uretersare two tubes take the urine from the kidneys to the bladder.

Bladderstores urine until it is removed.

Urethrais a tube that removes urine from the bladder


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The Skeletal System

The skeletal system is composed of 206 bones. It has several roles in the body.

It allows the body to stand upright and support its weight

It protects vital organs such as the heart and lungs

It allows movement It makes red and white blood cells

The skeletal system also contains

Ligamentswhich join bones together

Cartilagewhich prevents bones from grinding against each other

Tendonswhich join muscles to bones

Muscleswhich move the bones


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Glossary

specialised cell, tissue, organ, digestive, oesophagus, intestine, circulatory, artery, vein,

capillary, respiratory, trachea, bronchi, alveoli, excretory, urea, kidney, ureter, bladder,

urethra, skeleton

Study Questions

1. Explain why multicellular organisms require specialised organs and systems.

2. Describe the role of these organs in the digestive system:

i) Mouth

ii) Oesophagus

iii) Stomach

iv) Small intestine

v) Large intestine

vi) Rectumvii) Anus

3. Draw a simple labelled diagram of the heart showing the four chambers, the valves,

arteries and veins and use arrows to show the direction that blood flows through it.

4. Describe the structure and function of arteries, veins and capillaries

5. What is blood made of? What does each part do?

6. Describe the role of these parts of the respiratory system:

i) trachea

ii) bronchi

iii) the alveoli in the lungs

7. Which gas does the blood

a) pick up at the lungs ?

b) take back to the lungs?

8. Name the excretory organs of the body.

9. Describe the role of these parts of the excretory system:

i) Kidneys

ii) Ureters

iii) Bladder

iv) Urethra

10. Draw a labelled diagram showing the arrangement of the kidneys, ureters, bladder

and urethra.

11. Describe the roles of the skeleton, ligaments, cartilage, tendon and muscles.


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Elements and Compounds

Elements

All matter is composed of elements. There are more than 110 known different types of

elements and their names are shown in the Periodic Table. Elements cannot be brokendown into simpler substances.

Metals And Non-Metals

There are two main groups of elementsmetals and non-metalsand they have specific

properties.

Metals

have a shiny, metallic lustre

have high melting point and boiling point

are solids at room temperature, except mercury which is a liquid conduct heat and electricity

are malleable, which means that they can be easily bent and formed into thin sheets

Examples of metals

(Gold) (Mercury) (Copper)


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Non-metals

have a dull lustre

have either low melting point and boiling point or very high melting point and boiling

point do not conduct heat and electricity, except for carbon

are brittle, which means that they break easily

Examples of nonmetals

(Carbon) (Neon) (Sulfur)

Compounds

A compound is made of two or more different elements joined together Compounds have

properties that are different to the elements that they are made of. The names of the

elements come from the elements that are in them. For example, the elements called

sodium and chlorine make the compound called sodium chloride.

There many different compounds on Earth with many different uses.

sodium chloride is table salt

water is essential for the survival of all living things

methane is found in natural gas and is used for cooking

sucrose, also called sugar, is used in cooking

octane is found in petrol and is used as a fuel in cars


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Compounds And Mixtures

A compoundcontains elements joined together. The amount of each element in the

compound is always the same. For example, water is always H2O and carbon dioxide is

always CO2.

A mixturecontains elements and/or compounds mixed together but not joined together.The amounts of each substance in the mixture are not always the same. Air is a mixture of

gases and sea water is a mixture of water and dissolved salts.

Chemical Reactions

A chemical reaction occurs when elements and/or compounds join together to form

different elements and/or compounds. There are several observable signs that a chemical

reaction has occurred.

the temperature of the mixture increases or decreases

a gas is produced a colour change occurs

a solid is formed


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Glossaryelement, melting point, boiling point, density, compound, chemical reaction, temperature

Study Questions1. What is an element?

2. Complete this table for the properties of metals and non-metals.

Property Metals Non-metals

Lustre

Heat conduction

Electricity conduction

Malleability

3. What are the chemical symbols for

a) hydrogen c) oxygen

b) magnesium d) zinc

4. What is a compound?

5. Name the compounds formed from these elements.

a) silver + chlorine c) lead + oxygen

b) tin + sulphur d) magnesium + iodine

6. Name the elements contained in these compounds.

a) magnesium oxide c) zinc chloride

b) aluminium sulphide d) nickel iodide

7. Name two common compounds and describe one use for each one.

8. Identify three changes that commonly take place during a chemical reaction.

9. What is an ore?

10. Explain how froth flotation is used to separate ores from rocks.

11. Identify two ways that metals are separated from ores and give an example for each

one.


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Energy

Types Of Energy

There are several types of energy found around us.

Potential energyis stored energy to be used later. It is found in a stretched elasticband, a wound up spring and an object raised above the ground.

Kinetic energyis found in moving objects.

Light energyis produced by the sun, artificial lights, burning chemicals and very hot

objects.

Heat energyis found in hot objects such as room heaters.

Sound energyis produced by vibrating objects such as musical instruments.

Electrical energyis changed by electrical appliances into other types of energy.

(Light energy) (Kinetic and Potential energy)

ENERGY CHANGES

Energy can change from one type to another. Electrical appliances change electrical energy

into different types of energy. For example,

a toaster changes electrical energy into heat energy to toast the bread

an iPod changes electrical energy into sound energy so that you can listen to music

a fan changes electrical energy into kinetic energy so that you can keep cool


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Law Of Conservation Of Energy

The Law of Conservation of Energy states that energy cannot be created or destroyed. It can

only be changed from one type to another.

Fossil FuelsCoal and petroleum are called fossil fuels because they are formed from the remains of

ancient living things. They take millions of years to form and are non-renewable, which

means that once they are used they cannot be replaced. They are used as fuel in vehicles.

They are also used as fuels in power stations to generate electricity.

Solar Energy

Solar energy comes form the sun. It is renewable which means that as it is used it can be

replaced because it is continually being supplied to Earth by the sun. It is used in solar cells

to produce electricity and in solar water heaters to heat water.


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Conduction Of Heat

Heat travels through solids by conduction. At the point where the object is heated, its

particles gain energy and vibrate faster, which causes them to collide with the particles next

to them and pass on their energy. When the neighbouring particles receive the energy, it

makes them also vibrate faster and pass the energy on to more particles. In this way, heattravels through the solid.

Metals are conductors of heat. This means that heat energy can travel though them from

one place to another. For example, saucepans are made with a metal base to conduct heat

from the stove into the food.

Plastics are insulators of heat. This means that heat energy cannot travel through them. For

example, the handle of a saucepan is made of plastic because it will not conduct heat and so

you can pick up the saucepan without burning your hand.

Convection Of Heat

When liquids and gases are heated, the heat travels in a circular motion called a convection

current. The diagram below shows how convection currents warm a room.


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Radiation Of Heat

Radiation is the transfer of heat energy by waves called infrared radiation. It does not need

a medium to travel through and so can travel through a vacuum. Heat travels by radiation

from the sun to earth and it travels the same way outwards from a fire.

Light coloured surfaces reflect more heat while dark coloured surfaces absorb more heat.This is why light coloured clothes and cars are cooler in summer than dark coloured ones.

The absorbing panels of solar water heaters are painted black so that the copper water

pipes inside them absorb heat from the sun to heat the water.


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Glossary

kinetic, potential, fossil fuels, solar energy, renewable, electric current, conduction,

convection, radiation

Study Questions1. Define these types of energy and identify objects or situations in which these types

of energy exist:

a) potential energy

b) kinetic energy

c) light energy

d) heat energy

e) sound energy

f) electrical energy

2. Energy can change from one type into another. What energy changes occur in theseelectrical appliances:

a) heater

b) CD player

c) stove

d) light globe

e) battery operated toy car

f) TV

3. What does the Law of Conservation of Energy state?

4. Coal and petroleum are non-renewable fossil fuels.

a) What does non-renewable mean?

b) What does fossil fuels mean?

5. What are coal and petroleum used for?

6. Solar energy is renewable. What does renewable mean?

9. What is solar energy used for?

8. Describe some situations in which heat is transferred by conduction.

9. Metals are heat conductors. What does this mean?

10. Plastics are heat insulators. What does this mean?

11. Describe some situations in which heat is transferred by convection.

12. Describe some situations in which heat is transferred by radiation.


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Force and Electricity

Forces

A forceis something that changes motion. This means that a force can get something to

stop go faster

go slower

change direction

change shape

A force can be a push, a pull or a twist.

Contactforces touch the object they are acting on. Some contact forces are friction, air

resistance and buoyancy.

Non-contactforces do not touch the object. Some non-contact forces are gravity, magnetic

forces and electric forces.

Force is measured on a spring balance in units called Newtons (N).

FRICTION

Friction is a force between two rolling or sliding objects. It is caused by the roughness of

surfaces and it acts to slow the objects down. Friction always acts in the opposite direction

to the objects movement. Rough surfaces have more friction than smooth surfaces.

Friction causes surfaces to wear away. Rubber wheels on skateboards and bikes become

thinner as they rub against the road.

Friction also produces heat. A car engine becomes hot as the pistons move up and down inthe cylinders.


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Electrostatic Forces

Electrostatic forces occur on objects that have become electrically charged after being

rubbed. Some objects become positively charged and others become negatively charged.

When electrostatically charged objects are brought near to each other

two positively charged objects will repel each other two negatively charged objects will repel each other

a positively charged object and a negatively charged object will attract each other

Electrostatic forces can be useful. They are used

to produce images in photocopiers

in paint spray guns to make paint stick to surfaces

to remove solid particles from smoke in chimneys

Electrostatic forces can be a nuisance. They

cause lightning

cause electric shocks when we touch door handles and cars

cause sparks that lead to explosions

An electric fieldis the area around an electric charge.


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Magnetic Forces

Magnetic forces are produced by magnets. These forces attract metals containing iron,

steel, nickel and cobalt.

The ends of a magnet are called polesthe north pole and the south pole.

When two unlike(different) polesnorth and southare brought together, they attracteach other.

When two like(same) polesnorth and north orsouth and southare brought together,

they repeleach other.

A magnetic fieldis the area around a magnet

Magnets are used

to keep refrigerator doors closed

to hold notes on the refrigerator door

in speakers


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Electric Current

An electric current is the movement of electric charges through a metal wire. The charges

carry electrical energy to appliances that then change the energy into other types of energy.

The diagram below shows a simple electric circuit containing a power supply, a lamp and

electrical wires.

Electromagnets

An electromagnetcontains an iron core surrounded by electric wires. It is a temporary

magnet because the iron core is magnetic only when electricity runs through the wires.

Electromagnets are used

in scrap-yard cranes to lift cars

in hospitals to remove a piece of steel from a patients eye

in the mouthpiece of a telephone in metal detectors at airports


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Glossary

force, spring balance, Newton, friction, electrostatic, field, magnetic, pole, electromagnet

Study Questions1. Describe one example of a force that is changing

a) shape

b) direction

c) speed

2. Which instrument is used to measure force in Newtons?

3. What is friction?

4. Describe two examples of friction occurring in everyday situations.

5. What must you do to an object to give it an electrostatic charge?

6. What happens when the following types of electrostatic charges are broughttogether?

a) two positive charges

b) two negative charges

c) one positive charge and one negative charge

7. Identify two everyday situations in which electrostatic forces are

a) useful

b) a nuisance

8. What is the meaning of the term magnetic substance?

9. Name two magnetic substances.10. What happens when the following types of magnetic poles are brought together

a) two north poles

b) two south poles

c) one north pole and one south pole

11. Identify two everyday situations in which magnets are used.

12. What do electric charges do in an electric circuit?

13. Identify some common electrical appliances and the energy changes that occur in

them.

14. Identify two everyday situations in which electromagnets are used


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Investigating Scientifically

Laboratory Equipment

Equipment 2D diagramBeaker

Measuring Cylinder

Conical Flask

Test Tube

Tripod and wire gauze

Bunsen Burner


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Retort stand with

clamp

Filter funnel

Test tube rack with test

tubes

Test tube holder

Evaporating dish

Crucible with lid

x


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Bunsen Burner

A Bunsen burner has two flames.

Yellow flame is the safety flame because it is easily seen when the Bunsen burner is not

being used.

Blue flame is the heating flame because it is hotter than the yellow flame and it does not

leave black soot on the glassware.

Hypothesis

A hypothesis (pl. hypotheses) is an intelligent guess or probable answer to a question. It is

based on previous experience, information gained from other sources and the results of

other experiments. A scientist plans and conducts an experiment to test a hypothesis. For

this reason, a hypothesis is written as a statement that can be proved or disproved by

experiment. Some hypotheses are:

Watering plants with soapy water stunts their growth

Tall students jump higher in high jump competitions than short students.


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Planning And Conducting A Valid, Reliable Experiment

A variable is a factor in an experiment that can change, eg, temperature, light.

A validexperiment tests the independent variable and keeps all other variables constant

/the same.

In a valid experiment one variable is changed during the experiment. It is called the independent variable.

one variable is measured or observed as it responds to the independent variable. It is

called the dependent variable.

all other variables are kept constant/the same.

The aim of the experiment is to investigate the effect of the independent variable on the

dependent variable.

A controlis the part of an experiment that is designed to show that the independent

variable being tested is responsible for the results observed. It is used as a standard against

which the results from the experiment can be compared and judged. It ensures that that the

results are due to the independent variable and nothing else. The control has everything the

same except that the independent variable is not included. For example, when testing the

effect of a fertiliser on plant growth, the control will have the same type of plants growing

under exactly the same conditions but without fertiliser. Note that in some experiments a

control is not possible.

A reliableexperiment repeats the method numerous times to minimise errors and

inaccuracies.

Planning A Method

When you are planning an experiment, ask yourself these questions:-

1. Which variable will I make different?

2. Which variables must I keep the same?

3. What will I measure or observe? What measuring instrument will I use?

4. What safety precautions must I take?

5. How will I record the results?

6. How many times will I repeat the experiment?

7. How will I analyse the results? Will I calculate averages? Will I draw a graph?


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Writing A Method

To write a method for an experiment, number each step and use this format:-

VERB NOUN CONDITION (when, where, how, how long?)

A simple way to write a method is to

a) write the steps for ONE form of the independent variable

b) write the phrase Repeat steps 1-? for the other forms of the independent variable

For example

1. Put 500g of sandy soil into a pot.

2. Plant 20 seedlings in the pot.

3. Place the pot in constant light.

4.

Add 100ml of water to the pot every day.

5. Measure the height of the seedlings with a ruler every day for 10 days.

6. Record results.

7. Repeat steps 1-6 four times.

8. Repeat steps 1-7 in 12 hours of light and 12 hours of darkness.

9. Repeat steps 1-7 in constant darkness.

Observations

Scientists collect information from experiments by making observations using their senses

and measuring instruments.There are two types of observations.

1) Qualitative observationsare descriptions in words, eg, the colour of a chemical. We use

our senses to make these observations. However the senses are limited and can be

unreliable.

2) Quantitative observationsare measurements involving numbers, eg, the temperature

of a liquid. We use measuring instruments to make these observations. Measuring

instruments increase our powers of observation. Where possible, scientists make

quantitative observations because they are more accurate.

a thermometer is used to measure temperature

a stopwatch is used to measure time

a balance is used to measure mass

a measuring cylinder is used to measure volume


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Tables

Data is presented in tables because this makes the data easy to understand, easy to see

relationships and easy to make comparisons.

Line GraphsA line graph is used to show a relationship between two variables that are measured. To

draw a line graph:

1. draw the axes.

2. label each axis with the name of the variable and a unit of measurement eg, mass (g).

3. choose a suitable scale for each axis. Mark numbers at regular intervals along the axis.

4. plot each point with a cross.

5. join crosses with a ruled line or a freehand line.

Graphs can be used to extract information, make calculations, show trends, make

comparisons, recognise patterns, make conclusions and predictions.

Conclusions

Making a conclusion from an experiment involves comparing experimental results with

those predicted from the hypothesis. If the experimental results agree with the predicted

results then the conclusion is that the hypothesis is supported. If the experimental results

disagree with the predicted results then the conclusion is that the hypothesis is rejected.

Glossary

laboratory, Bunsen burner, test tube, beaker, tripod, gauze, measuring instrument,

thermometer, stopwatch, balance, measuring cylinder, hypothesis, valid experiment,

reliable experiment, independent variable, controlled variable, dependent variable,

qualitative observation, quantitative observation, procedure, table, graph, conclusion


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Living Things

Cells

All living things are made of cells. The parts of a cell are

nucleuscontrols everything that happens inside the cell cell membraneprotects the cell and gives it its shape. It has tiny holes that allow

materials to enter and leave the cell

cytoplasma jelly-like substance that fills the cell. Most cell functions occur here.

cell wallin plant cells only. It is located on the outside of the cell membrane gives the

plant its shape and stiffness

chloroplastsin plant cells only. They contain chlorophyll for making food for the plant.

(Animal Cell) (Plant Cell)

Unicellular And Multicellular Organisms

A unicellularorganism is made of one cell only. Bacteria are unicellular organisms.

Unicellular organisms reproduce by cell division. This means that their cells divide in half to

produce two new cells.

Bacteria can be either helpful of harmful.

Helpful bacteriaare used to

break down human faeces in sewage

treat industrial waste

decompose dead plants and animals

make yoghurt and cheese

produce drugs for treating diseases

Harmful bacteriacause diseases.

(Bacteria)


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A multicellularorganism is made of more than one cell. Most organisms are multicellular.

Classification Keys

Scientists use classification keys to identify unknown objects and organisms. The most

common type of key is the dichotomous key which has two choices at every point. It startsat the top with one group and slowly subdivides until no more choices are possible.


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Vertebrate Groups

Vertebratesare animals with backbones. There are five groups of vertebrates.

1)Mammals

are endothermic (warm-blooded) have hair or fur over their skin

have lungs for breathing

feed their young with milk from mammary glands

2)Birds

are endothermic (warm-blooded)

have feathers over their skin


lay eggs

3) Reptiles

are ectothermic (cold-blooded)

have dry scaly skin


lay eggs


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4)Amphibians

are ectodermic (cold-blooded)

have smooth, moist skin


lay eggs

5)Fish

are ectodermic (cold-blooded)

have moist, scaly skin

have gills for breathing

lay eggs

Adaptations In Vertebrates

Many vertebrates have special features in their appearance or behaviour to help them live

in their environment. These features are called adaptations. For example,

desert foxes are the same colour as the desert sand and they have very large ears that

lose heat to keep the body cool. It rests in its cool underground den during the day and

comes out at night to hunt for food.

polar bears have layers of fat under the skin and thuick white fur on top to keep them

warm. The white fur also helps them to blend in with their surroundings. They have fur

covering the soles of their feet to protect them from the snow and long curved claws to

help them grip the ice and their prey.


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4) Flowering Plants

have leaves, roots and stems

reproduce by seeds produced in flowers

Adaptations In PlantsMany plants have special features to help them live in their environment. These features are

called adaptations. For example,

desert plants have a variety of adaptations in their leaves to reduce water loss. Some

leaves are rolled into spikes, some leaves are covered in shiny hairs or have a shiny

surface to reflect the Suns heat, some leaves hang vertically so that the Sun does not h it

their surface.

mangrove plants grow in muddy, salty water. They have a dense mass of rots that help

to stabilise the mud. Also, the roots are adapted so that they do not take in too much

salt with the water and the leaves remove salt from the plant.

Glossary

cell, nucleus, cytoplasm, cell membrane, unicellular, multicellular, microorganism, bacteria,

classification, classify, characteristics, features, vertebrate, mammal, reptile, amphibian


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Study Questions

1. Draw a labelled diagram of a plant cell showing the nucleus, cytoplasm, cell

membrane and cell wall.

2. Describe the function of the following cell structures

a) nucleusb) cytoplasm

c) cell membrane

d) cell wall

3. What is the difference between a plant and an animal cell?

4. What is a unicellular organism? Give an example.

5. What is a multicellular organism? Give an example.

6. How do unicellular organisms reproduce?

7. Identify one way that bacteria can be harmful.

8. Identify one way that bacteria can be helpful.9. Name the five vertebrate groups.

10. Describe the features of the five vertebrate groups.

11. Describe some adaptations of vertebrates to their environment.

12. Describethe features of these plant groupsmosses, ferns, conifers, flowering

plants.

13. Describe some adaptations of plants to their environment.


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Matter

Matter, Mass, Volume And Density

Matteris all of the substances that make up objects in the universe.

Massis the amount of matter in a substance or object. Mass is measured on a balance andis given in grams (g) and kilograms (kg).

Volumeis the amount of space that a substance or object takes up. The volume of a liquid is

measured with a measuring cylinder and is given in millitres (mL) and litres (L).

Densityis the mass of 1cubic centimetre (cm3) of a substance or object. Density is measured

in grams per cubic centimetre (g/ cm3).

States Of Matter

All matter is made of tiny particles that are too small to be seen. The three states of matter

are solids, liquid and gases.

In solids, the particles are packed closely together and they are held tightly together.

They cannot move around but can only vibrate from side to side. This is why solids have a

definite volume and a definite shape and they cannot be compressed into a smaller

volume. An example of a solid is steel.

In liquids, the particles are close together and they are held loosely together. They can

roll over each other. This is why liquids have a definite volume but take the shape of their

container. They cannot be compressed into a smaller volume. An example of a liquid is

water.

In gases, the particles are a long way apart and are free to move anywhere in the

container. This is why gases have no definite volume and no definite shape and they can

be compressed into a smaller volume. An example of a gas is oxygen.


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Expansion And Contraction

Expansionoccurs as follows. When a substance is heated, its particles gain energy and so

they move faster. This causes the particles to collide more often and push each other

apart so that they take up more space. As a result, the substance expands. Railway tracks

are laid with gaps between them. When they are heated, they expand and fill the gaps.Without the gaps, they would buckle.

Contractionoccurs as follows. When a substance is cooled, its particles lose energy and

so they move slower. This causes the particles to collide less often and come closer

together so that they take up less space. As a result, the substance contracts. Overhead

electricity cables hang loosely between the poles. When they are cold, they contract and

become shorter. If they did not hang loosely, they would snap.

Change Of State

When substances are heated and cooled they often change state. There are five changes of

state.

meltinga substance is heated and changes from solid to liquid

evaporationa substance is heated and changes from liquid to gas

sublimationa substance is heated and changes from solid to gas

condensationa substance is cooled and changes from gas to liquid

freezinga substance is cooled and changes from liquid to solid

Melting Point And Boiling Point

Water melts at 0

OC

freezes at 0OC

evaporates at 100OC

condenses at 100OC

0OC is the melting point of water

100OC is the boiling point of water

The melting pointof a substance is the temperature at which it changes from solid to liquid

or liquid to solid.

The boiling pointof a substance is the temperature at which it changes from liquid to gas orgas to liquid.


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Glossary

balance, measuring cylinder, matter, mass, volume, solid, liquid, gas, particle,

compressibility, expansion, contraction, evaporation, condensation, melting, freezing,

Study Questions1. What is matter?

2. What is the meaning of the word mass?

3. Which piece of equipment is used to measure the mass of an object?

4. What is the meaning of the word volume?

5. Which piece of equipment is used to measure the volume of an object?

6. Name the three states of matter.

7. Describe the movement of particles in solids, liquids and gases.

8. Using the particle model, describe and give reasons for the volume, shape and

compressibility ofa) solids

b) liquids

c) gases

9. Using the particle model of matter, explain why a metal expands when it is heated

and contracts when it is cooled.

10. Describe an example of a situation in which a substance

a) expands

b) contracts

11. Which change of state occurs when a substance freezes?

12. Which change of state occurs when a substance melts?

13. Which change of state occurs when a substance evaporates?

14. Which change of state occurs when a substance condenses?

15. What is the melting point of water?

16. What is the boiling point of water?

17. Complete this table of changes of state to show whether particles gain or lose

energy and move faster or slower.

Change of State Energy Move

Gain Lose Faster Slower

melting

evaporation

condensation

freezing


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Mixtures

Pure Substances And Mixtures

The materials around us can be grouped into pure substances and mixtures.

Pure substancescontain only one substance. They always have the same properties no

matter where they come from. Examples are sugar, gold, pure water and helium gas.

Mixturesare substances that have several different pure substances mixed together. Examples

are lipstick, concrete, soft drink and air.

Solute, Solvent And Solution

A solublesubstance is a substance that dissolves. An insoluble substance is a substance that

does not dissolve.

When a solutedissolves in a solvent, it forms a solution. In a sugar solution, the sugar is the

solute and the water is the solvent.


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Some solutions are coloured and some are colourless but all solutions are transparent.

A dilutesolution contains a small amount of solute in the solvent.

A concentratedsolution contains a large amount of solute in the solvent.

A saturatedsolution is a solution that cannot dissolve any more solute

The Importance Of Water As A Solvent

Wateris a very important solvent because it dissolves many substances in a wide variety of

situations. For example,

many drinks, such as fruit juice and soft drink, are water solutions

almost all chemical reactions in the human body occur between substances dissolved in

water in the cells and the blood

water dissolves minerals in the soil and carries them into plants through the roots

many industrial chemicals, such as acids, are made by dissolving chemicals in water.

Filtration And Sieving

Filtrationis a method of separation that uses a filter to separate an insoluble substance

from a mixture. A filter contains tiny holes that trap the insoluble substance but let the rest

of the mixture pass through. Filters are used to separate

dirt from water in swimming pools

dirt from petrol and oil in cars

dust from air in vacuum cleaners

coffee grounds from coffee in a coffee machine solid particles from air in a mask

A sieveis also a filter but with larger holes. Sieves are used to separate

spaghetti from water in a colander

tea leaves from tea in a tea strainer


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Evaporation And Crystallisation

Evaporationand crystallisationare used to separate soluble substances from solutions. In

this process, the solvent evaporates and the solute crystallises. Evaporation and

crystallisation are used to obtain salt from seawater.

Distillation

Distillation is used to separate pure water from solutions. In this process, the solution is

boiled, the steam is collected and then cooled and turned back into liquid water. This water

is pure and is called distilled water. Distillation is used to obtain pure water from sea water

and is called desalination.

Magnetic Attraction

Magnetsattract substances made of iron. Magnetic attraction is used to separate iron and

steel from mixtures. For example, it is used in can recycling centres to separate iron cansfrom aluminium cans.


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Chromatography

Chromatographyis used to separate small amounts of chemicals from a solvent. In this

process, the chemicals are dissolved in a solvent and then the solvent is allowed to soak

through a material such as filter paper. Some chemicals are carried through the filter paper

faster than others. This means that they travel different distances along the filter paper andso they are separated. If the chemicals are different colours, they can be clearly seen on the

filter paper. Chromatography is used to detect

colours in ink

harmful pesticides in food

drugs in urine samples

Glossary

pure substance, mixture, dissolve, soluble, insoluble, solute, solvent, solution, dilute,

concentrated, filtration, sieving, evaporation, crystallisation, magnetic attraction,

chromatography

Study Questions

1. Sugar is soluble in water. What does soluble mean?

2. In a saltwater solution, what is the

a) solute?

b) solvent?

3. What is the difference between a dilute solution and a concentrated solution?

4. How would you separate these mixtures in a lab:

a) salt from saltwater?

b) iron nails from sawdust?

c) powder from water?

d) colours in ink?

5. Describe one use of

a) filtration or sieving

b) evaporation and crystallisation

c) distillation

d) magnetic attraction

e) chromatography


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Planet Earth

Structure Of The Earth

The Earth is a huge ball of rock. It is made of four layers.

crustmade of solid rock mantlemostly made of solid rock with some molten rock in a layer called the

asthenosphere

outer coremade of molten iron and nickel

inner coremade of solid iron and nickel

The lithosphereis the name given to the layer of solid rock in the crust and upper mantle.

Minerals

A mineral is a chemical compound that is found in the Earths crust, either on its own or

with other minerals in rock. Therefore every rock is made of two or more minerals.

Types Of Rocks

There are three types of rocks.

1) igneous rocksare formed when magma and lava cool

2) sedimentary rocksare formed when sediments are compacted or cemented together

3) metamorphic rocksare formed when igneous rocks and sedimentary rocks are put

under intense heat or pressure


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Weathering And Erosion

Weatheringis the breaking down of rocks into small fragments called sediments. Two types

of weathering are

physical weatheringrocks are broken down into small fragments by physical factors in

the environment such as extreme temperature changes

chemical weatheringrocks are changed into new substances by chemical factors in

the environment such as acid rain.

Erosionis the process of moving fragments of weathered rock to other places. This is done

by agents of erosion such as wind, rivers, waves and glaciers.

Water Cycle

The water cycle continually supplies Earth with fresh water. It is called a cycle because it has

no beginning and no end and so it never stops. The three stages of the water cycle are

evaporationwater on Earths surface changes from liquid to vapour and rises into the

atmosphere

condensationwater vapour in the atmosphere changes from vapour to liquid and

forms clouds

precipitationliquid water in the atmosphere falls to the Earths surface as rain, snow

or hail.


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The Atmosphere

The atmosphere is a mixture of gases surrounding the Earth. It is made of several layers

the troposphere, stratosphere and ionosphere. About 78% of the atmosphere is nitrogen

and 21% is oxygen. The remaining 1% is a mixture of numerous gases including carbon

dioxide, neon, helium, methane, hydrogen and ozone.The carbon dioxide in the atmosphere traps heat from the sun to keep the Earth warm but if

the amount of carbon dioxide increases too much, the Earth will heat up. This called the

greenhouse effect.

The layer of ozone in the atmosphere blocks out more than 95% of the suns UV rays. If the

ozone layer is damaged so that it has holes in it, then too much UV light will reach the

Earths surface causing sunburn and skin cancer.

Glossary

core, mantle, crust, lithosphere, mineral, weathering, erosion, deposition, sedimentary,igneous, metamorphic, evaporation, condensation, precipitation, atmosphere, ozone,

greenhouse

Study Questions

1. Draw a labelled diagram showing the core, mantle, crust and lithosphere.

2. What are minerals?

3. Explain how these rocks form:

a)

igneousb) sedimentary

c) metamorphic

4. Rocks are weathered by physical change and chemical change. Explain one example of

each.

5. Draw a labelled diagram of the water cycle showing where evaporation, condensation

and precipitation occur.

6. In the water cycle, what happens in

7. evaporation

8.

condensation9. precipitation?

10.Which two gases make up most of the atmosphere? What is the percentage of each one

in the air?

11.What is ozone needed for?

12.What is carbon dioxide needed for?


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Producers and Consumers

Water Transport In Plants

The rootsof a plant take in water.

The stemof a plant transports water from the roots to the leaves through tubes calledxylem.

The leavesof a plant have tiny holes called stomata that release excess water into the air in

a process called transpiration.

Many Australian plants have adaptations that allow them to live in high temperature, low

water environments. These include

Leaves rolled into spikes to reduce the number of stomata

Leaves that hang vertically to keep the leaf cool by reducing the amount of sunlight

striking the surface of the leaf

Leaves that have a shiny, waxy covering that keeps the leaf cool by reflecting sunlight

Photosynthesis

Photosynthesis is the process in which plants make their own food. They combine water and

carbon dioxide in a series of chemical reactions driven by energy absorbed from sunlight by

the chlorophyll in the leaves. The products of photosynthesis are glucose and oxygen. The

glucose is used as food for the plant and the oxygen is released into air to be used by plants

and animals.


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Respiration

Respiration is the process in plants and animals that uses glucose and oxygen to produce

energy. The energy is used for growth, repair and reproduction.

Respiration is closely linked to photosynthesis because photosynthesis in plants provides the

glucose to be used in respiration in plants and animals.

Producers, Consumers And Decomposers

Plants make their own food in photosynthesis. Animals obtain their food by eating plants

and/or other animals.

Plants are called producersbecause they make their own food.

Animals are called consumersbecause they obtain their food by eating plants and other

animals. There are three types of consumers.

Herbivoreseat plants only

Carnivoreseast animals only

Omnivoreseat both plants and animals

Some organisms, such as bacteria, are decomposers. They feed on the wastes and dead

remains of plants and animals. They break down the wastes and remains into carbon

dioxide, water and minerals which then go back into the air and soil to be reused by plants.


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Food Chains And Food Webs

A food chainshows how energy is passed on from one organism to another. Each organism

in the chain obtains food by eating the organism before it. The first organism is a producer,

such as a plant, because it makes its own food. The other organisms are consumers. The first

consumer is a herbivore and then the others following it are either carnivores or omnivores.A food chain is shown below.

In any place there are numerous food chains. They can be combined into a food webto

show the complete picture of feeding relationships in that place. A food web is shown

below.

Bushfires, Drought And Flood

Bushfireshave both negative and positive effects on the environment. They destroy large

areas of vegetation and many of the animals living in those areas. With the vegetation

removed, the soil is exposed to wind and water and so it is easily eroded. However, some

Australian plants need fire for their seeds to begin growing and so they regenerate quickly

after fires. Ashes from the fire provide nutrients for the soil that allow plants to recover and

seeds to grow quickly. Some Australian animals survive fires by either quickly moving away

from fires or sheltering in burrows or logs, allowing them to return to the area after the fireand quickly repopulate it.


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Drought

Drought creeps up over a number of years when rainfall is low. The effects can be

devastating to wildlife as well as to farmers. Drought kills native plants and animals as well

as crops and livestock and the destruction of vegetation leads to soil erosion. Drought

depletes lakes and rivers, causing the death of many aquatic plants and animals. Finally,drought increases the chance of bushfire, dust storms and toxic algal blooms in rivers.

Flood

Floods cover vast areas of land, submerging plants and animals and causing their

destruction. They also wash away soil, causing soil erosion. However, floods can also have

positive effects on ecosystems. They replenish ground water and soil water, they wash

excess salt from the soil and they provide water for fish and other animals in arid areas to

breed.

Glossary

xylem, stomata, transpiration, photosynthesis, respiration, ecosystem, producer, consumer,

decomposer

Study Questions

1. Describe the role of roots in water absorption.

2. Describe the role of the stem in water movement.

3. What are xylem?

4. Describe the role of the leaves in transpiration.5. What are stomata?

6. In which part of the plant does photosynthesis occur?

7. Which materials are needed by plants for photosynthesis?

8. Which materials are produced by plants for photosynthesis?

9. Which materials are needed by plants for respiration?

10. Which materials are produced by plants for respiration?

11. Why are photosynthesis and respiration important for all living things?

12. Name one Australian ecosystem.

13. Using an example of a food web, describe how the producers, consumers and

decomposers are related.

14. Discuss some effects on Australian ecosystems of

a) bushfires

b) drought

c) flood


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Space

Models Of The Universe

Earth-centred model

In ancient times when there was no technology for looking at the universe, people couldonly use their eyes to make observations. They saw the Sun rise in the East and set in the

West and concluded that the Sun was moving across the sky. Aristotle used his observations

of planets and stars in the night sky to propose an Earth-centred model of the universe. In

this model, the Earth was the centre with the planets and stars moving in circular orbits

around it.

Sun-centred model

Aristarchus was the first astronomer to suggest that the Sun was at the centre of the

universe. He used his observations and estimates of the relative sizes of the Sun, Earth and

Moon and their distances from each other to argue that it was more logical to place the

largest object, the Sun, at the centre rather than the smaller Earth. He claimed that the

apparent motion of the planets and stars was due to the Earth rotating on its axis once per

day.

With the invention of the telescope, more accurate observations could be made which

confirmed the Sun-centred model.

Earth centred model Sun centred model


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Gravity

Gravity is a force that attracts objects. All bodies in space have gravity that attracts other

objects in space towards them. For example, the Suns gravity attracts the planets and keeps

them in orbit around it. The Earths gravity keeps the Moon in orbit around it. It also keeps

objects on the surface of the Earth. For an object to leave Earth, it must exert a forcegreater than the Earths gravitational force.

Tides

Tides are periodic rises and falls of large bodies of water. They are caused by the

gravitational pull of the Moon and the Sun on the Earth.

The gravitational pull of the Moon on the Earth causes the oceans to bulge out in the

direction of the Moon. They bulge out on the other side because the Earth is being pulled

towards the Moon and the water in the oceans is left behind. The Sun has less effect on the

tides but when the Sun and the Moon line up (New Moon and Full Moon), very high tides,

called king tides or spring tides, occur.

Light And Sound

Light is a form of energy that does not need a medium (material) to travel through. It travels

at 300,000 km/s and it can travel through a vacuum. Light from the Sun travels 150 million

kilometres through the vacuum of space to Earth in 8 minutes.

Sound is a form of energy that does need a medium to travel through and so it cannot travelthrough a vacuum. It travels through air at 340 m/s. Because there is no air on the Moon,

sound does not travel on the Moon as it does on Earth.


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Space rock that lands on the Earths surface without completely burning up is called a

meteorite.

Stars

Beyond the solar system are galaxies of stars.

A staris a sphere of gas, mainly hydrogen and helium, that produces its own heat and light

by nuclear reactions.

A galaxyis a group of millions or billions of stars held together by gravity.

A nebulais a cloud of gas and dust in space that eventually becomes a star.


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Light Year

A light year is equal to the distance travelled by light in one year. Large distances in space

are measured in light years rather than kilometres.

Glossaryaxis, rotation, revolution, hydrosphere, solar system, star, galaxy, nebula, light year

Study Questions

1. What is the difference between an Earth-centred model of the universe and a Sun-

centred model?

2. Describe the observation/s that led Aristotle to propose an Earth-centred model of

the universe.

3. Describe the observation/s that led Aristarchus to propose a Sun-centred model of

the universe.4. Which technology provided evidence for the Sun-centred model?

5. Explain why Earth has day and night.

6. What is the name given to the time taken for the earth to revolve once around the

sun?

7. Explain why Earth has the seasons.

8. Explain why Earth has tides.

9. Explain why light energy travels on Earth and in space but sound energy only travels

on earth and not in space.

10. Name the eight planets in our solar system in order from the sun.11. What is a

a) comet?

b) asteroid?

c) meteor?

d) meteorite?

12. What is the role of gravity in our Solar System?

13. What is a

a) galaxy?

b) star?

c) nebula?

14. What is a light year?

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