1. Improper disposal of waste can cause:
a) air pollution
b) water pollution
c) sickness and diseases
d) acid rain
e) flash floods

A Air pollution
1. Air pollution occurs when there are lots of gaseous waste materials in the air.
2. The gaseous waste materials include dust and smoke that contain harmful substances.
3. Smoke is released into the environment when forest are burnt or when fuels are burnt in vehicles and factories.
4. Air pollution can be caused by the following:
a) open burning
b) Burning of fuels in factories and motor vehicles
c) Forest fires
d) Spraying of insecticides and other chemical substances

1. To avoid pollution, we must dispose of waste properly.
2. Disposal of waste from housing areas
a) Rubbish must be thrown into rubbish bins, and not burnt or thrown into drains
b) Rubbish must be wrapped properly in a plastic bag and tied before it is thrown away.
c) Rubbish is collected by garbage trucks to be sent to waste disposal centres.
3. The collected rubbish will be disposed of in two ways.
a) The rubbish is dumped in layers at a large site called a landfill. The rubbish is compressed using a steamroller.
b) The landfill site must be safe from flooding is heavy rain occurs and also far from housing areas.
c) In some places, the rubbish is burned in an incinerator.
4. A lot of rubbish like old newspapers, aluminium cans, glassware and some plastics can be recycled. Before we throw our rubbish away, we should separate it up into different groups.
5. Waste water from factories, homes, schools and offices is usually channeled into the sewage system.
6.The sewage is treated in sewage treatment plants to make it safe before it is discharged into the sea.
7. Factories should be fitted with long chimneys. Filters are fixed on the chimneys to reduce the release of air pollutants.

1. People throw away tons of rubbish every day.
2. If this great amount of waste is not disposed of properly, our land will be polluted. Our surroundings would be dirty and smelly.
3. Some of the improper ways of waste disposal are shown below.

Waste Materials

1. Waste is any material that is no longer useful.
2. In their daily activities, people dispose many types of waste, including used paper, empty packages and food leftovers.
3. Waste materials can be divided into three types.
a) Solid waste such as glass, wood, paper, plastic, metal and food leftovers.
b) Liquid waste such as oil, detergent, chemical waste and sewage.
c) Gaseous waste such as vehicle smoke, cigarette smoke, pesticides and toxic gases.
4. Waste materials come from various sources.

Bahan Buangan

1. Bahan buangan ialah sebarang benda yang tidak berguna lagi.
2. Setiap hari,manusia membuang pelbagai jenis bahan buangan termasuklah kertas, bungkusan kosong dan sisa makanan
3. Bahan buangan boleh dibahagikan kepada 3 jenis
a) Bahan buangan pepejal seperti kaca, kayu, kertas, plastik, logam dan sisa makanann.
b) Bahan buangan cecair seperti minyak, detergen, bahan buangan dan kumbahan.
c) Bahan buangan gas seperti asap kenderaan, asap rokok, racun perosak dan gas toksik.
4. Bahan buangan datangnya daripada pelbagai sumber.

1. Food preservation gives many benefits to us.
a) The food will last longer
i) With preservation processes, perishable products such as fruit and vegetables, meat and fish can be kept for a long time.
ii) Food can be marketed to far places overseas. This can increase income in the agricultural sector.

b) The food is easy to store and distribute
Canned foods are much easier to store and distribute from one place to another compared to raw foods.

c) Food wastage is reduced
i) Excess food can be kept in a refrigerator for the next meal.
ii) Without preservation, perishable foods like vegetables and fruits cannot be eaten a few days after harvesting.

2. Food preservation is very important to fulfill the food supply needs in a country.
3. It ensures that food supply can be distributed to the people at all times.
4. Furthermore, problems like food shortage or famine can be avoided.

1. Food can also be preserved with salt. This process is called salting.
2. Salting can be done in two ways as shown below.
a) Adding a lot of salt to the food.
b) Soaking the food in a salt solution.
3. Bacteria and fungi cannot grow in salty conditions. Hence, salted foods last longer.
4. Examples of food that can be preserved by salting are fish, meat, eggs, vegetables and fruits.
5. Salting will change the taste, colour and destroy food nutrition.

1. Pasteurising is a process in which milk is heated at 63 °C for 30 minutes or heated at 72 °C fo 15 seconds and followed by rapid cooling to below 10 °C.
2. The pasteurised milk can then be refrigerated to last a few days.
3. Friut juice can also be preserved in this way.
4. This method of preservation retains the natural flavour of milk. Nutriens like vitamins are not destroyed.

1. Some foods can be canned and bottled. The canning and bottling of food allows the food to be kept for a very long time.
2. These methods of preservation involve:
a) heating of the food to a very high temperature
- can kill bacteria and fungi
b) keeping foods in airtight cans or bottles
- to prevent the entry of air that may contain bacteria and fungi
3. Therefore, canned or bottled foods can be kept for a long time in months or years.
4. Examples of food that can be perserved by canning or bottling are shown below.

• fish
• meat
• beans
• corn
• mushroom
• chicken
• pineapple
• condensed milk
• jam
• soft drink
• soy sauce
• syrup
• tomato sauce
• fruit juice
  

1. Food can be preserved by soaking it in an acidic solution (vinegar) or saturated sugar solution. This process is known as pickling.
2. Bacteria and fungi cannot grow in acidic conditions or in saturated sugar solutions.
3. Therefore, pickled foods last longer and cannot be spoilt easily.
4. However, its taste will be different and it becomes less nutritions.
5. Examples of food that can be preserved by pickling are fruits such as mango, papaya and guava.
6. Mango pickling can be done as follows.
a) Cut some green mangoes.
b) Wash and drain the mango slices.
c) Mix the mango slices with salt and leave them overnight.
d) Wash and drain the mango slices again.
e) Soak the mango slices in sugar solution for several days.
f) Add a little bit of vinegar an seal the bottle tightly.

1. Cooling ia a process in which foods are kept at low temperature (0°C - 5 °C).
2. Examples of food preserved by cooling are vegetables, friuts, eggs, margarine, cheese and milk.
3. Freezing is a process in which food is cooled at a very low temperature (below 0°C) until it freezes.
4. Examples of food preserved by freezing are fish, meat, chicken, prwans, cuttlefish, meat balls and ice-cream.
5. Cooling and freezing can be done by keeping the foods in a refrigerator at home.
6. In the case of cooling, the idea is to slow bacterial action so that it takes food much longer (perhaps a week or two) to spoil.
7. In the case of freezing, the idea is to stop bacterial action altogether. Frozen bacteria are completely inactive.
8. Bacteria and fungi becomes active again when the food is taken out from the refrigerator.
9. Therefore, after taking out food from the refrigerator, it must be cooked or eated quickly before spoils.
10. The advantages of preserving food by cooling and freezing are :
a) the freshness a food is preserved.
b) nutrition content in the food is not destroyed

1. Boiled foods may last longer than unboiled foods.
2. When food is boiled, all bacteria and fungi will be killed.

1. We can dry food to remove water from the food.

2. Without water in food, bacteria and fungi cannot grow. This can make the food last longer.

3. Drying foods can be done as follows.

a) Drying the food under hot sun

b) Heating food to a high temperature

4. The disadvantage of this method is that the food becomes less nutritious because some nutrition may be lost during the process.

1. Food preservation is a process that makes food last longer.
2. Food preservation can prevent or slow down the action of bacteria or fungi on the food.
3. There are many methods to preserve food.

• Drying
• Boiling
• Cooling
• Vaccum packing
• Pickling
• Freezing
• Bottling & Canning
• Salting
• Smoking
• Pasteurising
• Waxing

Food Spoilage

1. Food can spoil after a certain period of time.
2. Spoilt food will change in texture and taste.
3. One can get food poisoning by eating spoilt food.
a) Food poisoning can lead to stomach upset, diarrhea and vomiting.
b) Serious food poisoning may cause death.
4. Foods which are spoilt can be identified by observing, touching, smelling and tasting.
5. Spoilt food has one or more of the following characteristics.
a) Unpleasant smell
b) Unpleasant taste
c) Changed colour
d) Changed texture
e) Mouldy

Calculation of Speed
1. The speed of an object can be calculated using the following formula.

Relationship between Speed and Time
1. To determine which object is faster, we can compare the time taken by the moving objects to travel in given distance.
2. The object which moves faster takes a shorter time to travel a given distance.

Hubungan antara Kelajuan dan Masa
1. Untuk menentukan objek mana yang bergerak lebih laju, kita boleh bandingkan masa yang diambil oleh objek untuk bergerak dalam jarak yang ditetapkan.
2.Objek yang lebih laju mengambil masa yang lebih pendek untuk melalui jarak yang ditetapkan.

Relationship between Speed and Distance
1. To determine which object moves faster, we can compare the distances travelled in a given time by two moving objects.
2. The object which moves faster travels a longer distance in a given time.

Hubungan antara Kelajuan dan Jarak
1. Untuk menentukan objek mana yang bergerak lebih laju, kita boleh bandingkan jarak yang dilalui dalam tempoh tertentu oleh kedua-dua objek.
2. Objek yang bergerak lebih laju melalui jarak yang lebih panjang dalam tempoh yang ditetapkan.

What is speed?
1. Speed is the distance travelled by an object per unit time.
2. Speed shows how fast an object moves.
3. Every moving object has speed. Only stationary objects have no speed.
4. The speed of a moving object can change. For example, a car can move fast or slow at different times.
5. Different objects have different speeds.

Apakah kelajuan?
1. Kelajuan ialah jarak yang dilalui oleh suatu objek dalam satu unit masa.
2. Kelajuan menunjukkan kepantasan objek bergerak.
3. Setiap objek yang bergerak mempunyai kelajuan. Hanya objek yang pegun tidak mempunyai tidak mempunyai kelajuan.
4. Kelajuan objek yang bergerak boleh berubah. Contohnya kereta boleh bergerak dengan laju atau perlahan pada masa yang berbeza.
5. Objek yang berbeza mempunyai kelajuan yang berbeza.

1. Friction cannot be eliminated.
2. Otherwise, friction can be reduced by using certian material as follows.
(a) Rollers
(b) Talcum powder
(c) Oil, wax, grease
(d) Air cushion
3. Rollers are found in many objects such as roller blades, trolleys, chairs and skateboards. They reduce friction by reducing contact between moving surfaces.
4. Oil, wax, grease and talcum powder are used as lubricants to reduce friction, so moving surfaces slide smoothly over one another. For example, oil is used to reduce friction between door hinges.
5. An air cushion (layer of air) under a hovercraft enables a hovercraft to glide easily above water.
6. Aircraf and traina are designed to have aerodynamic shapes to reduce friction friction so that air flows smoothly. Smooth air flow means that less fuel is needed for higher speeds.

1. Frictional force brings many advantages and disadvantages in our lives.
2. The advantages of friction are as follows.

Underline the correct words.

1. If the spring is (pulled, pushed) it becomes extended.

2. Rubber bands become (shorter, longer) when pulled.

3. A can becomes (pieces, dented) when it is hammered.

4. Plasticine becomes (flat,thick) when it is pressed.

5. A glass (breaks, dented) into pieces when it is dropped onto the floor.

A. Write True or False

1. A force can change the speed of a moving object. _____________

2. A force applied in the same direction of a moving object will cause the object to stop. _________

3. A force can change the direction of a moving object. ___________

4. A force makes a stationary object move. ___________

5. A force equally applied to a moving object makes the object move faster.__________

1. A force can
a) move a stantionary object
b) change the motion of an object
c) change the shape of an object
2. During a football game, we can clearly observe the effects of a force to the motion of an object.

A Force Can Move a Stationary Object

1. A stationary ball will move when it is kicked.
2. A force is applied to the ball when it is kicked. This force causes the ball to start moving.
3. The ball moves in the same direction as the applied force.
4. The ball will move faster or roll further it we kick harder.

A Force Can Changes the Motion of an Object
1. The direction of the force applied to an object will determine its motion.
2. A moving ball will move faster if a force is applied in the same direction of its motion.
3. On the other hand, a moving ball will move slower if a force is applied in the opposite direction of its motion.
4. Also, a moving ball will change its direction when a force is applied from another direction when a force is applied from another direction of its motion.
5. A force can cause a moving object to stop.
a) For example, when a goalkeeper catches a moving ball with his hands, the ball will stop.
b) The goalkeeper exerts an opposing force on the moving ball by catching it.

A Force Can Change the Shape of an Object
1. A force can cause the shape of an object to change.
2. The changes of the objects when a force is applied may be temporary or permanent depending on the physical characteristic of the object.
3. Elastic objects such as the spring and rubber band only change shape when force is applied to them.
4. When the force is removed, the object returns to its original shape.
5. When force is exerted on a fragile object, the object will be broken apart. The change of shape is permanent.

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