Classification of materials

1. Matter is anything which occupies space and has mass.
2. Matter includes both living and non-living things.
3. It is with our five senses that we recognise matter and most of its properties. Colour, size, shape are some of the common physical properties where our sense of sight is used.
4. Materials have both similarities and differences amongst them. Choice of a material for various purposes depends on the properties of the material.

Reflections on Term 3 Science

My science results for term 3 was 80/100 and I personally felt that this could be improved for my end-of-year despite a massive improvement of 20 marks as compared to term 3. I studied hard for science and hoped to be able to achieve better for my end-of-year

Hydroponics farm visit

On 26th May 2011, the Science Department organised a learning journey for the secondary 2 I-Spark students.About 20 students went to Oh Chin Huat Hydroponics Farm located at Yishun.

We were assigned to a guide who explained very clearly the various stages of growing crops using the hydroponic method. While explaining, the guide also showed us how crops such as onions, butterhead lettuce and other crops are grown in the greenhouse.

We also had an exciting and interesting quiz session towards the end of the tour. Those who got right answers to the questions brought home a small potted plant each. Before we boarded the bus back to school, all teachers and students were each given a packet of butterhead lettuce.

Nutrient cycles in the ecosystem

1. The cycles in nature maintain a balance in the ecosystem, which ensure that all living things are able to live and grow.
2. Recycling is important because natural resources are limited.
3. Organisms that feed on dead plants and animals are called decomposers. Decomposers play a major role in recycling.
4. Circulation of carbon through and ecosystem is called the carbon cycle.
5. The only process, which removes carbon from the atmosphere, is photosynthesis. Carbon is added to the atmosphere during respiration by living things and due to decomposition of dead and decayed matter.
6. The continuous cycle through which nitrogen in the form of nitrogenous compounds is removed from the soil and returned to it is called the nitrogen cycle.
7. Nitrogen is removed from the soil due to absorption of nitrogenous compounds by the roots of the plants and by the action of denitrifying bacteria.
8. Nitrogen is returned to the soil by the process of nitrogen fixation by root nodules of leguminous plants, by the action of certain free living bacteria and by the decomposition of plant./animal wastes by certain bacteria.
9. Addition of fertilizers increase the nitrogen content of the soil.
10. Carbon and nitrogen cycles are important because, carbon forms a part of carbohydrates, proteins and fats; while nitrogen forms a part of proteins, which are used to build tissues in living things.

Energy transfer in ecosystem

1. The prime source of energy in living things is the sun. Energy from the sun enters the ecosystem through the plants (photosynthesis) and the flow of energy within an ecosystem can be shown by food chains and food webs.
2. The food chain shows the feeding relationship between living things. Each organism in the food chain is called a link.
3. A food chain starts with green plants which are the producers. Animals that eat only plants are the primary consumers and animals that eat other animals are called the secondary consumers.
4. Interconnected food chains constitute a food web.
5. As energy passes along a food chain, the amount of energy transferred gradually decreases due to energy lost to the environment at each link. Only about 10% of the energy available at one link in a food chain is passed on to the next link.
6. The number of organisms decrease from one link to another along the food chain. This gives a pyramid of numbers for living things.
7. The balance between the number of plants and animals in and ecosystem is called the balance of nature.

Ecology: Living things in and ecosystem

1. A place where plants and animals live is called habitat (eg) ponds, rocks, trees etc.
2. The environment of an organism is affected by physical factors such as sunlight, temperature, wind, pH and biotic factors such as all the living things.
3. Plants and animals have special body features or ways of behaving which help them to survive. There are called adaptions.
4. Owls are adapted to see in the night, polar bears are adapted to hibernate in the winter and so on.
5. Cactus plant is adapted to grow in deserts. They have thick and juicy stems to store water and their leaves are modified into spines.
6. Aquatic animals are adapted to live in water with less oxygen. They come to the surface to take in air.
7. pH value of water and soil also affect the organisms living in a habitat.
8. In any habitat there is usually more than one kind of organism, which depend on each other for food, shelter and protection and constitute to biotic factor.
9. Different plant and animal population living together in a habitat constitute a community. The habitat, together with the community of organisms living in it, forms an ecosystem.
10. Various physical factors and biotic factors affect life in and ecosystem. Organisms interact with each other in an environment and are adapted to live in an environment.
11. Human activities such as deforestation and over hunting damage our ecosystem. It is important to conserve the world's ecosystem and to use them wisely. 

Transmission of heat energy

1. Heat or thermal energy is one of the vital energy source on earth. This heat energy needs to be transferable if life processes on earth are to continue. Heat is a form of energy that flows from a region of   higher temperature to another of lower temperature.
2. The three main types of heat transfers are
   (i) conduction,     (ii) convection and    (iii) radiation
   
   (i) Conduction:
        - The process of heat transfer, where there is no physical visibility of matter moving from their
          position, but pass heat in the form of kinetic energy is called as conduction.
        - Those substances which are capable of conducting heat are called as conductors and those
          substances through which heat cannot pass through are called as insulators.
        - Usually metals are good conductors of heat, while wood, thermacoal, plastics, ceramic are
          examples of insulators. Vacumm is considered to be the best insulator.
   (ii) Convection:     - Fluids, (liquids and gases) are usually bad conductors of heat. In fluids heat travels by the
          process called convection. Here the molecules themselves move, carrying the heat energy with
          them in the form of kinetic energy.
        - The upward movement of the hot fluid and the downward movement of the cold fluid causes the
          movement in the fluid called the convection current.
        - Land and sea breeze are caused by convection current.
   (iii) Radiation:     - The transfer of heat energy from the sun through vacuum in the form of electromagnetic waves
           is called radiation.
        - The sun gives off heat energy in the form of rays or radiant energy. When these rays fall on an
           object, they are absorbed and the object gets heated up.
        - All hot bodies give off radiant heat even if they are not glowing. White, silvery or highly polished
           surfaces are good reflectors of radiant heat. Black or dark bodies are good absorbers of heat.
           Good absorbers of heat are also good radiators.
3. Heat absorbed or given out due to radiant energy depends on
   (i) Colour of the object     (ii) Texture of the object     (iii) Surface area     (iv) Temperature
   Black and rough surfaces absorb and radiate more heat energy than light and smooth surfaces. Objects with more surface area and at high temperature absorb and radiate more heat energy than the objects with low temperature and less surface area.
4. Applications of conduction, convection and radiation
   Conduction: Pans used for cooking are made of metals, while the handles are made of insulators.
   Convection: Boiling of water in an electric kettle, land and sea breeze.
   Radiation: Black umbrellas, rough black surfaces behind refrigerators.
5. Thermos flaskVacuum flasks also called commonly as Thermos flask maintains the hot or cold temperature of the contents inside. It reduces the heat transfer from inside which could occur by the three modes viz conduction, convection and radiation. The flask is made in such a way that heat is not lost or gained by conduction, convection and radiation. Thus, the temperature inside a thermos flask is maintained.