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1. Science is the study of natural things around us such asrainbow and cloud formation.

2. In the study of science, we investigate and makeobservations of nature and events occuring around us.

3. Scientific knowledge is acquired through scientificmethods.

4. Five physical quantities and their SI units

5. Mass is the quantity of matter in an object.6. The mass of an object is measured using the lever

balance or beam balance.7. Weight is the force of gravity acting on an object and

its SI unit is newton (N).8. The weight of an object is measured using the spring

balance or compression balance.9. The differences between mass and weight

10. The length of a curve can be measured using a threadand a ruler.

11. The area of an irregular object can be estimated byusing the graph paper.

12. The volume of liquid can be measured using theburette, measuring cylinder or pipette.

13. The water displacement method is used to measurethe volume of irregular objects.

14. Prefixes used in measurements have their own valuesand symbols.

15. Standard units are important for internationalcommunications.

Introduction to Science1 Cell as a Unit of Life2

Matter3

2. Cells are very small and can only be seen through amicroscope.

3. The main components of a cell include the nucleus,cytoplasm and cell membrane.

4. Every structure in a cell has its own function.5. Plant cells and animal cells are different in shape and

structure.6. Unicellular organisms such as the Amoeba and

yeast have only one cell.7. Multicellular organisms such as the Spirogyra and

Hydra consist of many cells.8. Multicellular organisms are usually big in size.9. Human body is made up of many types of cells and

these cells differ in shapes and sizes.10. Human cells are organised into tissues, organs and

systems.11. The tissue is a group of similar cells, for example, the

muscle cells and nerve cells, which carry out the samefunctions.

12. The organ is a group of different tissues, for example,the kidney and lungs, which carry out the samefunctions.

13. The system is a group of different organs, forexample, the digestive system and respiratory system,which carry out the same functions.

14. Cell specialisation allows separation of work to becarried out by cells in the body.

15. Many life processes cannot be conducted without theorganisation of cells.

Physical quantity SI unitTime second (s)Mass kilogram (kg)Length metre (m)Temperature kelvin (K)Electric current ampere (A)

Mass WeightThe amount of matter The force of gravity in an object pulling on an object Remains the same Changes from place

to placeSI unit is kilogram (kg) SI unit is Newton (N)Measuring tools are Measuring tools arebeam balances and spring balances and lever balances compression balances 1. Matter is anything that has mass and occupies space.

2. Matter is made up of small and discrete particles calledthe atoms.

3. It is present in three states, namely solids, liquidsand gases.

4. The solid consists of particles which are closelypacked together. The particles vibrate at their fixedpositions only.

5. The liquid consists of particles which are arrangedclose together and move randomly.

6. The gas consists of particles which are far apart andmove freely in all directions.

7. The random movement of liquid and gas particles iscalled the Brownian movement.

1. The basic resources on Earth include water, air, soil,minerals, fossil fuels and living things.

2. The importance of the resources on Earth

Resources Importance

Water For systems of living things to function;in homes for drinking, cooking and washing; for transportation and in industries

Air For breathing, for combustion and for photosynthesis

Soil Habitat for living things; for agriculture, construction and mining

Minerals Used in the construction industry; in the production of utensils, electrical products and ornaments

Plants and For food, clothing, fuels and building animals materials

3. An atom is the smallest particle in matter.4. A molecule is made up of two (or more) atoms. The

atoms may be of the same or a different type.5. An element is a substance that cannot be split into

two (or more) simpler substances. It consists of thesame kind of atoms.

6. A compound is made up of two or more differentelements which are chemically combined together.

7. A mixture is formed when two or more substancesthat do not react chemically, are added together.

8. The properties of metals and non-metals

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8. The density of an object is the mass per unit volume ofthat object.

massDensity = ————volume

9. A less dense object will float on a liquid which isdenser. A denser object will sink in a liquid which isless dense.

10. An object which initially sinks can be modified to makeit float by making its surface larger.

11. The concept of density is used in the building of ships,submarines and floats, and also in the transportation oftimber logs.

The Variety of Resourceson Earth

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Metals

Shiny, ductile, malleable,high melting point, highdensity, good conductorsof heat and electricity

Non-metals

Dull, brittle, low meltingpoint, low density, poorconductor of heat andelectricity

Properties

9. Comparison between compounds and mixtures

10. Components of mixtures can be separated by means ofevaporation, filtration or distillation.

11. A mixture of iron filings and powdered sulphur can beseparated by using a magnet.

12. A mixture of salt and sand can be separated bydissolving, filtering and evaporating the mixture.

13. Intelligent use of resources can be attained by theconservation of natural resources: to prevent thedestruction of the environment, the extinction of speciesand the onset of natural disasters.

14. We should recycle materials such as glass, plastic andaluminium.

15. Activities that can deplete the Earth’s resources includemining, logging, agriculture and clearing of land forbuildings.

Properties Compound Mixture

Preparation Chemical means Physical means

Changes in Yes Notemperature

New substance Yes Noformed

Characteristics Different from Same ascomponents components

Composition Fixed Not fixed

Separation Chemical means Physical means

The Air Around Us5

1. Air is a mixture because its composition varies fromplace to place and from time to time.

2. Composition of air

Composition of air

Nitrogen 21%

Oxygen 78%

Carbon dioxide 0.03%

Inert gases 1%

Water vapour Varies

Dust and microorganism Varies

3. Properties of oxygen and carbon dioxide

Properties Oxygen Carbon dioxide

Colour, odour and taste None NoneSoluble in water Yes Yes

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Properties Oxygen Carbon dioxide

Soluble in sodium No Yeshydroxide solutionSupports combustion Yes NoAcidic No Yes

4. (a) Confirmation test for oxygen: oxygen rekindles aglowing splint.

(b) Confirmation test for carbon dioxide: Carbondioxide turns lime water cloudy.

5. Respiration is a process where food is oxidised toproduce energy, water and carbon dioxide.

6. The process of respiration isGlucose + oxygen → energy + carbon dioxide + water

7. All living things obtain the energy for life processesfrom respiration.

8. Comparison of inhaled air and exhaled air

9. Combustion is the chemical combination of oxygenand a substance to produce heat and light.

10. Three requirements for combustions are(a) a substance that can burn(b) oxygen(c) heat

11. Combustion of carbon isCarbon + oxygen → carbon dioxide + energy

12. Combustion of hydrocarbon isHydrocarbon + oxygen → carbon dioxide + water

+ energy13. Air pollution is the presence of unwanted and

harmful substances in the air.14. Sources and effects of air pollutants

Contents Inhaled air Exhaled air

Oxygen 21% 16 %

Carbon dioxide 0.03% 4%

Nitrogen 78% 78%

Water vapour Varies Saturated

Temperature Same as the Body environment temperature

Pollutants Effects Sources

Carbon Prevents blood Burning of carbonmonoxide from absorbing and emissions

oxygen, causing from exhaust pipeheadaches of vehicles

Oxides of Damages lungs Burning of fuel nitrogen and causes acid in factories and

rain emissions from exhaust pipe of vehicles

Pollutants Effects Sources

Sulphur Causes breathing Burning of coal dioxide difficulties and and petrol in

acid rain factories

Lead Causes brain Burning of leadedcompounds damage petrol

Carbon Greenhouse effect Combustiondioxide

Dust and Dirty buildings, Smoke from smoke irritate lungs and factories,

poor visibility forest fire and dusts from the ground

15. Cigarette smoke contains pollutants such as nicotine,tar, carbon monoxide and carcinogens.

Sources of Energy6

1. Energy is the ability to do work. We use energy towalk, talk and breathe.

2. Energy exists in various forms such as kinetic energy,potential energy, mechanical energy, heat energy, lightenergy, sound energy, electrical energy, chemicalenergy and nuclear energy.

3. Potential energy is the energy stored in an object.An object has the potential energy because of its stateand position.

4. Moving objects have kinetic energy.5. Hot objects give out heat energy.6. Chemical energy is the energy stored in fuels, food

and batteries.7. Electrical energy is produced by the flow of

electrical charges. 8. Sound energy is produced through vibrations.9. Nuclear energy is the energy stored in the nucleus

of an atom.10. Mechanical energy involves the kinetic and

potential energy.11. Renewable energy sources can be used

continuously and will not deplete.12. Non-renewable energy cannot be replaced when

depleted.13. Sources of renewable and non-renewable energy

14. The sun is the primary energy source.15. Energy can be changed from one form to another.16. Energy converters are equipments or substances

Renewable energy Non-renewable energy sources sources

Hydro, solar, wind, Coal, petroleum, natural biomass, waves, gas, nuclear, tidal, geothermal

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that convert energy from one form to the other. 17. Alternative energy sources such as water, the Sun,

biomass and wind are available in large amounts. Theadvantages of these forms of energy are, they are cleanand do not pollute the environment.

18. Efficient use of energy means using energy with minimalwastage.

19. Alternative energy sources must be identified toreplace non-renewable energy.

20. We need to conserve non-renewable energy becausetheir sources are limited. Lesser use of the non-renewable energy will also reduce the harmful effectson our health and environment.

21. Energy sources must be used efficiently so that we cancontinue to use the energy sources for a longer time.

Heat7

1. The Sun is the primary source of heat energy. 2. Heat energy causes an object to become warmer or

hotter.3. Heat can be produced through friction, chemical

reactions, electricity and by burning fuels. 4. Heat is measured in joules (J). 5. Temperature is a measure of degree of hotness or

coldness of an object.6. A thermometer is used to measure the temperature in

degree celsius (°C).7. Substances of the same temperature may not contain

the same amount of heat.8. Comparison between heat and temperature

9. Solids, liquids and gases expand when heated andcontract when cooled down.

10. Heat is transmitted through conduction, convection andradiation.

11. Conduction is the transfer of heat from one particle toanother without movement of the particles involved.

12. Metals are good conductors, liquids (except mercury)are poor conductors and gases are very poorconductors of heat.

13. Convection is the transfer of heat by the movementsof heated particles.

14. Liquids and gases transmit heat by convection.15. Land and sea breezes are examples of natural

convection currents.16. Radiation is the transfer of heat in the form of

electromagnetic waves. The rate of transfer is the sameas the speed of light.

17. Uses of good and bad conductors

18. When heated, a solid changes to a liquid and then to agas.

19. When a gas cools down it changes to a liquid andthen to a solid.

20. The physical processes involved in the change of state are melting, boiling, freezing, evaporation, condensationand sublimation.

21. Physical processes are required for a change of state tooccur.

22. Applications of expansion and contraction(a) Solids: bimetallic strips in oven and fire alarm,

rivets, gaps in railway tracks, rollers in steel bridges, metal wheels of trains

(b) Liquids: thermometers(c) Gases: hot air balloons

23. Dull, black surfaces are good absorbers and radiatorsof heat.

24. White and shiny surfaces do not absorb and radiateheat well.

Heat Temperature

A form of energy A measure of degree of hotness or coldness of an object

Measured in joule Measured in kelvin (K) or celsius (°C)

Transferred from a hot Depends on the heat of body to a cold body the body

Good conductor Bad conductor (Insulator)

Cooking utensils Plastic and wooden handles

Thermometers Styrofoam containersSoldering irons BlanketsElectrical instruments CorkCar radiators Fibre glass and felt in walls

of refrigerators

Physical process Change of state

Melting Solid to liquid

Boiling, evaporation Liquid to gas

Freezing Liquid to solid

Condensation Gas to liquid

Sublimation Solid to gas