Summary of Primary Science Knowledge

Theme	Lower Block knowledge	Upper Block knowledge
Diversity	There're living things and non-living things. Living things are classified into plants, animals (birds, fish, insects, mammals), fungi (mushrooms, yeast) and bacteria. Non-living things can be classified into the different materials they're made of. Types of materials include plastics, wood, rubber and metals.
Cycles	Some life cycles have 3 stages. Examples: Seed --> young plant --> adult plant Birds: egg --> chick --> adult Amphibians: egg --> tadpole --> adult Cockroach: egg --> nymph --> adult Some life cycles have 4 stages. Examples: Butterfly: egg --> caterpillar (lava) --> chrysalis (pupa) --> adult Mosquito: egg raft --> wriggler (lava) --> tumbler (pupa) --> adult	Sexual reproduction involves the fusion of male sex cells and female sex cells. We say that the female sex cells are fertilised. In humans, the male reproductive system produces male sex cells called sperms, while the female reproductive system produces female sex cells called eggs or ovules. Fertilization occurs in the oviduct or fallopian tubes in the female reproduction system. The fertilized egg then develops into a fetus in the uterus or womb. Flowers are the reproductive system of flowering plants. Anthers produce pollens, while the ovary produces ovules. Pollination occurs when pollens are transferred from the anthers to the stigmas by wind or by animals. Tubes then extend from the pollens through the style to the ovary. This brings the male gametes to the ovules in the ovary. Fertilization occurs in the ovary. After fertilization, the ovary grows into a fruit and the ovules become seeds. By wind, water or animals, the seeds are dispersed away from the parent plant. When conditions (warmth, air, water) are right, the seeds germinate and seedlings grow out.
	Matter can take different physical states, solid, liquid, gas. Heat can be supplied or removed to change the state of matter. Melting or liquefaction: solid (+ heat) --> liquid Evaporation or boiling: liquid (+ heat) --> gas Condensation: gas (- heat) --> liquid Freezing or solidification: liquid (- heat) --> solid	Water exists in three interchangeable states ice, water and water vapour or steam depending on the temperature. For water, melting (ice --> water) and freezing (water --> ice) occurs at 0 ºC boiling (water --> steam) occurs at 100 ºC. The water cycle is a cycle that occurs in nature. Evaporation of water from seas, lakes and rivers: water --> water vapour Condensation of water vapour on dust particles: water vapour --> fine water droplets Fine water droplets combine together to form heavier water droplets. Heavy water droplets then fall as rain.
Systems	The parts of a plant are the leaves (to make food through photosynthesis), the roots (to absorb water and minerals from the soil) and stem (to conduct materials between the leaves and roots). The air is a mixture of gases such as nitrogen, oxygen, carbon dioxide and water vapour. When there's sunlight, the leaves take in carbon dioxide from the air to photosynthesise and give out oxygen to the air. Like all living things, plants also take in oxygen and give out carbon dioxide all the time.	Living things are made of smallest living units called cells. Plant cells and animal cells are similar in that they contain cell membrane 9to allow some substances to pass through), cytoplasm (where chemical reactions occur) and a nucleus (to contain genetic materials). The plant cell has a cell wall (to provide shape and rigidity) and chloroplasts (to make food through photosynthesis) but the animal cell doesn't. The transport system of the plant consists of two separate sets of tubes. One set of tubes carries water from the roots to other parts of the plant. The other set of tubes carries sugar from the leaves to other parts of the plant.
	The human body consists of a number of body systems working together. The skeletal system provides shape to the body and supports the body. The muscular system enables movement. The respiratory system takes in oxygen from the air and releases carbon dioxide into the air. The circulatory system helps to transport materials around the body. The digestive system breaks down food and absorbs the food. In the digestive system, only the mouth, stomach and small intestine produce different digestive juices to break down food into small pieces which can pass through the small intestine into the blood stream.	In the lungs of the respiratory system, oxygen in the inhaled air passes into the bloodstream, while carbon dioxide in the blood passes into the air. The carbon dioxide-rich air is then exhaled. In the circulatory system, the heart pumps oxygen-rich blood from the lungs to all parts of the body, and oxygen-poor blood from all parts of the body to the lungs. The heart also pumps nutrient-rich blood from the small intestine to all parts of the body.
		A simple electrical system may consist of the battery (to supply electrical energy), connecting wires, a switch and a lamp (to convert electrical energy to light). An electric current can only flow in a closed circuit. Materials can be electrical conductors (e.g. Metals) and electrical insulators (e.g. Plastic, ceramic, rubber, wood). We can use a simple circuit tester to help test for electrical conductors. An electric circuit can be in series, in parallel or both. In a series circuit, when one lamps blows, the circuit becomes open and the other lamps don't light up. In a parallel circuit, when one lamp blows, current can still flow in the other branches and the other lamps still shine. The greater the current through a lamp, the brighter it shines. We can increase the brightness by using more batteries in series or lesser number of lamps in series.
Interactions	Forces between magnets are attractive if unlike poles face each other, or are repulsive if like poles face each other. Magnets can also attract some magnetic materials such as iron, cobalt and nickel.	Forces are interactions between objects that have the following effects: A force can move a stationary object A force can speed up or slow down a moving object A force can make a moving object change direction A force can stop a moving object A force can change the shape and size of an object (e.g The spring stretches when it is pulled by a force.) Types of forces: Frictional forces occur between surfaces that rub against one another. Friction can be reduced by lubricants. The weight of an object is the force of gravity between the object and the Earth. Weights cause all objects on the Earth to fall towards the centre of the Earth. Elastic spring stretches when it is pulled by a force. The spring also exerts an elastic spring force when it stretches. The longer its extension, the greater the elastic spring force.
		The Sun's energy enters the ecosystem via plants (producers). This energy is then passed on to the consumers (preys, predators) through food relationships called food chains or food webs. Different habitats (e.g. Garden, grass field, pond, seashore, tree) support different kinds of organisms. The survival of an organism depends on temperature, amount of light, availability of food, types of other organisms (e.g. Predators, parasites). Different organisms have their own structural or behavioral adaptations to cope with physical factors (e.g. Cold climate), obtain food, escape predators, and reproduce by finding and attracting mates or dispersing seeds. Man's activities have positive and negative impacts on the environment. Deforestation and pollution (air, water, land) leads to a loss of habitats by plants and animals. This, together with other activities such as over-hunting, leads to the extinction of some species and we have lesser biodiversity. Global warming occurs when there is an overall increase in temperature in the Earth's atmosphere. This is caused by an increased amount of greenhouse gases (e.g. Carbon dioxide, methane) in the atmosphere. Deforestation and motor vehicles contribute to the increased carbon dioxide level in the atmosphere.
Energy	Light and heat are two forms of energy. Light from luminous objects (e.g. Candle flame, fluorescent lamp, the Sun) is energy that enables us to see non-luminous objects (e.g. Books, the Moon). Temperature (measured in ºC) is a measure of how hot or how cold an object is. When two objects of different temperature are in contact with each other, heat flows from the hotter object to the colder object. The temperature of the hotter object decreases because it loses heat. The temperature of the colder object increases because it gains heat. Good conductors of heat (e.g. Metals) are materials that allow heat to pass through easily. Metals are cold to the touch because they conduct heat away from your skin. Poor conductors of heat (e.g. Air, plastics, wood, rubber) are materials that do not allow heat to pass through. When matter is heated, it expands. When matter is cooled, it contracts. Gases expand more than liquids which expand more than solids for the same temperature rise. Matter also changes in state when it gains or loses heat.	Energy (measured in J) is the capacity to do work. Most of our energy is traced back from the Sun. Our food provides us with the energy to do work and for our body to carry out life processes. The energy stored in our foods comes from plants and animals. The energy is then traced backward through the food chain and eventually to the Sun. Different forms of energy: Kinetic energy is the energy of movement. The greater the speed of a moving object, the greater is its kinetic energy. Gravitational potential energy is the energy possessed by an object that is positioned above the ground. The greater the height above the ground, the more gravitational potential energy the object stores. Light energy Electrical energy Sound energy Heat energy Energy can be converted from one form to another. Examples: Torch: chemical energy (in batteries) --> electrical energy (in wires) --> heat + light (from light bulb) Catapult: elastic potential energy (as catapult is stretched) --> kinetic energy (of flying stone) --> sound (when hitting an object) Diver jumping from a diving board: gravitational potential energy (due to her position above water) --> kinetic energy (as she speeds up during the fall) --> sound (of splashing) Fuel power station: chemical energy (in fuel) --> heat (from burning) --> kinetic energy (moving steam which turns turbines) --> electrical energy (from generators)