The sky turns dark before it rains. Do you know why?

ANSWER

The clouds are too dense with water droplets that they prevent the sunlight from penetrating through. We explain this with the help of science.

1.1 INTRODUCTION OF SCIENCE

CHAPTER 1

WHAT IS SCIENCE?

Science is the systematic study of nature and how it affects us and our environment.

Science help us to understand the natural phenomena we see around us. Natural phenomena are happenings that occur in nature.

WHICH OF THE FOLLOWING IS A NATURAL PHENOMENON?

Air pollution

Apple falling down from a tree

Construction of a dam

Formation of rainbow

Importance of science:-

a)It helps us to understand ourselvesb)Science helps us to understand our

environment.c)It makes our life more comfortable.

Information produced from the study of science is known as scientific knowledge. This knowledge is always expanding as scientists make new discoveries every day.

Benefit of science Domestic- Appliances e.g washing

machine, vacuum cleaners, tap waterTransportation-vehicles, roadsAgriculture-tractors, fertilizer, pesticidesCommunication-mobile phones, e-mail,

internetMedicine-better surgical techniques and

equipment

CAREERS IN SCIENCEBotanist- specialist in plantsZoologist- specialist in animalsChemist- A person trained in chemistryAstronomer- A person who studies

astronomyAstronaut- A person trained to travel in a

spacecraftSurgeon-performs medical operations

1.2 HAZARDOUS SUBSTANCES FOUND IN THE LABORATORY

-MISS NURUL AIN ASHIKIN BT HALIN-

POISONOUS

CAUSES DEATH OR HARM IF ABSORBED THROUGH SKIN, SWALLOWED OR

INHALED.E.g.: mercury, bromine,

sodium cyanide

FLAMMABLE

• BURNS EASILYE.g. ethanol, petrol

and kerosene.

CORROSIVE

• CAUSES DAMAGES TO SKIN AND EYES UPON CONTACT

• E.g. concentrated sulphuric acid & concentrated sodium hydroxide

IRRITANT

CAUSES DISCOMFORT TO THE BODY

E.g.: ammonia and chloroform

IRRITANT

RADIOACTIVE

GIVES OUT RADIATIONE.g.: plutonium and

uranium

EXPLOSIVE

• EXPLODES EASILY• E.g. sodium and

potassium

LABORATORY APPARATUS

APPARATUS FUNCTIONS

Test Tube Hold small amounts of liquid & for carrying out reactions.

Test Tube Holder

Hold a test tube when it is being heated.

Beaker Contain chemicals and for carrying out reactions.

Conical flask Contain chemicals and for carrying out reactions.

Spatula Pick up solid chemicals.

Thermometer Measure temperature.

Retort Stand To hold or clamp apparatus.

Filter funnel Transfer liquid into a container

Tripod stand Support apparatus such as beakers when heating them.

Pipette To measure a fixed volume of a liquid.

Burette To measure a small volume of a liquid accurately.

Test tube rack

To place test tubes while we are not using them.

Measuring cylinder

To measure the volume of liquids.

Evaporating dish

Evaporate liquid

Bunsen Burner• To heat things.• Got 2 types of flames.

Luminous flame (yellow flame)

Non-luminous flame (blue flame)

When the air hole is closed

When the air hole is opened

Easy to see because it is luminous

Difficult to see because it is non-luminous

Gives out a lot of soot Does not give out soot

Is not so hot compared to blue flame

Is very hot

Is not suitable for heating

Suitable for heating

1.3 STEPS IN A SCIENTIFIC INVESTIGATION

PROCESS SKILLS IN SCIENCE

• Scientists obtain the knowledge of science by doing scientific investigations. • Scientific investigations involve

the use of process skills in science.

• Process skills in science include: a)Asking questions (why, what, when, how)b)Making observation (use the senses) c) Taking measurements (thermometer,

analytical balance) d)Recording data collected (table, sentences) e)Analyzing and interpreting data (graph)f) Making conclusionsg)Writing reports to communicate the results.

STEPS IN SCIENTIFIC INVESTIGATION

Identifying the problem making hypothesis controlling variables planning experiment

collecting data analyzing & interpreting data

writing a report making conclusion

1.4 Physical Quantities and Their Units

Physical Quantities

Are quantities that can be measured.Physical quantities are measured in S.I units.S.I is an abbreviation for the French term Le Systeme International d’ Unites. It means International System of Units.

Example of physical quantities and their S.I units

Physical Quantity S.I unitLength Metre (m)

mass Kilogram (kg)

Time second (s)

Temperature Kelvin (K)

Electric current Ampere (A)

Using prefixes in measurements

We usually use prefixes when the quantities we measure have very big values or very small values.The use of prefixes make it easier for us to write the measurements.

Prefix Symbol True value of the symbol

Value of the symbol in the standard form

tera T 1000 000 000 000 X1012

giga G 1000 000 000 X109

mega M 1000 000 X106

kilo k 1000 X103

deci d 0.1 X10-1

centi c 0.01 10X-2

mili m 0.001 10X-3

micro μ 0.000001 10X-6

nano n 0.000000001 10X-9

piko P 0.000000000001 10X-12

PHYSICAL QUANTITIES

Rewrite the values of these measurements using prefixes:

a) 90000 g = … kgb) 300 m = … mmc) 0.0055 kg = … gd) 0.04 km = … me) 8.3 mg = …kgf) 3.8 mm = …km

exercise

g) 3.4 kg = … gh) 8500 cm = … mi) 9800 000 μs = …..sj) 320 g = ….kgk)450 m = … kml) 12 500 000 m = …Mmm)4900 mg = …kg

1.5 Concept of Mass and weight

Concept of weight

• Weight of an object is the force of the gravitational pull that acts on the object.

• It can changes as it depends on the gravitational attraction that acts on the object at a given place.

• The S.I unit for weight is newton (N)• Weight is measured by using a spring balance

or a compression balance.

spring balance

compression balance

Concept of mass

• Is quantity of matter that is present in the object.

• It is fixed although it may be moved to different places.

• It doesn’t influenced by the force of the gravitational pull.

• S.I unit for mass is kilogram (kg).• Is measured by using a lever balance, a triple

beam balance or an electronic balance.

Lever balance

Triple beam balance

Electronic balance

differences between weight and mass

Weight Mass

Due to pull of the Earth on the object

The amount of matter in the object

Measured by spring balance or compression balance

Measured by lever balance, triple balance or electronic

balance.Value is not always the same,

depends on where it is measured.

Fixed and does not depend on where it is measured.

S.I unit is Newton S.I unit is Kilogram

1.6 Use of Measuring Tools

Measuring length

• Length is usually measured in units of kilometres, metres, centimetres and milimetres.

• S.I unit for length is metre (m). • Tools for measuring length: a) the metre ruler, half-metre ruler or ruler b) the measuring tape c) external and internal caliper

The metre ruler, half-metre ruler or ruler

To measure the length of short straight lines.

Correct eye position is very important in order to obtain an accurate reading.

The measuring tape

To measure the length of long straight lines.

The length of a curved line

1) Using thread and a ruler -Tie a small knot/make a mark with a pen near

the end of a piece of cotton thread. -Lay the thread along the curved line a little at

a time. -then, measure the length of the thread with

a ruler.

The length of a curved line2) Opisometer (map measurer) &

ruler

External and internal calipers

• We can use calipers together with a metre ruler, to measure the diameters of round or cylindrical objects.

• External calipers: external diameter of an object.

• Internal calipers : internal diameter of an object.

Internal Diameter

Internal Caliper

External Diameter

External Caliper

Measuring Area

• We can estimate the area of regular or irregular shapes by tracing the shapes onto a piece of graph paper.

Method:

1) Count the number of complete squares.2) An incomplete square is counted if half or

more of the square is covered. 3) Do not count an incomplete square if less than half of the square is covered.

Measuring Volume

• We often need to measure the volume of liquids.

• We use a measuring cylinder, burette or pipette to measure the volume of a liquid.

• We usually measure the volume of a liquid in mililitres (ml) and the volume of a solid in cubic centimetres (cm3).

Burette

Pipette

Measuring cylinder

• Correct eye position is very important when taking readings from the scale of a measuring tool.

• To find the volume of a regular object and irregular object.

• In this method, the object is dropped into a measuring cylinder. This will cause the water level in the measuring cylinder to rise. The water level rises because the water in the measuring cylinder has been displaced by the object.

Water Displacement Method

y mL

x mL

• The volume of water displaced = y-x• The volume of the stone = The volume of

water displaced. = (y-x) ml = (y-x) cm3

conclusion

• We can measure physical quantities accurately by using a suitable measuring tools.

• The accuracy of our measurements can be improved by:

a)Avoiding parallax error.b)Using a hand lens to help us to see the scale

more clearly.

Importance of standard units in everyday life

CHAPTER 1.7

• The use of standard units make it easier for people from different countries to communicate with each other.

• The use of a standard unit means a measurement in that unit has the same value anywhere in the world.