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Year 6 - Sc Note

Transcript of Investigating materials


2. FOOD SPOILAGEAll food turns bad or spoilt after a certain period of time.Characteristics of spoilt food:1. Unpleasant smell2. Unpleasant taste3. Change colour4. Change texture5. Mouldy 3. FOOD SPOILAGEFOODCHARACTERISTICBread and cakes Turns mouldy with black, green or white dots orhairy patchesHas unpleasant smell and tasteBecome slimyVegetablesTurn yellowishBecome soft and witheredBecome slimy and wateryFruitsBecome bruisedTurns mouldyHas unpleasant smell and taste 4. FOOD SPOILAGEFOODCHARCTERISTICFish and meat Has unpleasant smellFlesh becomes sunken when pressedHas pale gills and sunken eyes in fishMilkSmells and taste sourBecomes curdled and foamyIts has swells (bulges)Canned food Tin can swells (bulges)Food in it smells bad 5. FOOD SPOILAGEFood become rotten or decayed foodWhy? Due to the microorganism mainly bacteria and fungiMicroorganism live and feed on the food. It breaks the food down into simpler substances. This process called decaying.When the food is decaying, it will smell and taste unpleasant and cause food poisoning when we eat.Microorganism need air, water, nutrients (food), moderate temperature and suitable acidity to grow. 6. FOOD PRESERVATION 7. FOOD PRESERVATIONInvolves treating food so it can be stored without spoiling for along time.Prevents or slow down the growth of microorganism on food.Killing the microorganism or making the condition unsuitable for them to growth and survival. 8. WASTE 9. TYPES OF WASTESome waste can be decayed and some cannot be decayedThe waste can be decayed by the microorganism is called biodegradable waste.The waste cannot be decayed by he microorganism is called non biodegradable wasteMostly biodegradable waste originated from living thing. For examples:1. Discarded food, sewage, animal waste, paper and wood2. Certain types of plastics known as biodegradable plastics and detergents known as biodegradable detergent.3. Effluent from factory that produce food or processes agricultural product such as palm oil and rubber 10. Biodegradable WasteDecaying and decomposition is a process of breaking a material down into simpler substances by microorganism.The biodegradable waste changes like the following:1. Change in appearance : It may change colour, become softer, become liquid or gas.2. Reduction in size and volume : For example, a huge heap of dried leaves will be come small heapIt can also be useful. The biodegradable waste can be used to make compost, nutrient-rich substance used as fertilisers. 11. Advantages and disadvantages ofwaste decayAdvantagesAllows nutrient in waste to be returned to the soil and bereused.Helps to reduce the volume of waste.DisadvantagesContribute to global warmingMethane is produced by the global warming. Methane is aflammable gas. It will cause the landfill catch the fire easilyespecially during the hot and dry season.Rubbish and sewage treatment plants give out the bad smell. 12. Non Biodegradable WasteNon biodegradable waste remain in the environment for a very long time.It cannot be decayed easily.For example : The plastic bag takes about 10 to 20 years to decay.We should reduce the waste by reused and recycle them.