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Energy (Types of energy (Light energy (Light is needed for us to see…

- - - - Temperature is a measure of how hot something is. It is measured in degree Celsius(°C)
        
        We can measure temperature by using a thermometer.
        
        We read a laboratory thermometer by
        
        1) Holding the thermometer upright in the container of liquid.
        2) Look at the level of the liquid in the thermometer.
        3) Position your eyes at the same level as the liquid in the
        thermometer.
        4) Read the marking nearest to the level of the liquid in the
        thermometer.
        
        Temperature is not heat.
        
        For example, let's say there are two beakers, Beaker Y and Beaker X. Beaker X has more water than Beaker Y. The temperature of the water in both beakers are the same. Beaker X has more heat than Beaker Y as a greater amount of heat is needed to warm a greater amount of water to the same temperature as a smaller amount of water.
    - - Heat loss
        
        Things become colder when they lose heat.
        
        .
        
        Changes in state of matter
        
        If a gas loses heat and is cooled past its boiling point, it changes from a gas to a liquid.
        
        If a liquid loses heat and is cooled past its freezing point, it changes from a liquid to a solid.
        
        .
        
        Contraction
        
        When a solid, liquid or gas is cooled, it contracts and the size of the solid, liquid or gas decreases.
      - Heat gain
        
        Things become hotter when they gain heat .
        
        Heat always travels from a hotter place to a colder place until both places reach the same temperature.
        
        Conductors of heat
        
        Good conductors of heat
        
        Good conductors of heat allow heat to flow through easily.
        
        Poor conductors of heat
        
        Poor conductors of heat do not allow heat to pass through them easily.
        
        Changes in state of matter
        
        If a solid gains heat and is heated past its freezing point, it changes from a solid to a liquid.
        
        If a liquid gains heat and is heated past its boiling point, it changes from a liquid to a gas.
        
        .
        
        Expansion
        
        When a solid, liquid or gas is heated, it expands and the size of the solid, liquid or gas increases.
  - - - Some objects give off light(known as light sources) while others don't.
      - We can see light sources as they give out light. We see other things only if there is light shining on them. The light is reflected from the object and enters our eyes.
      - Different types of materials allow different amounts of light to pass through them.
    - - The shadow of an object usually has the same shape as the object.
        
        A shadow formed using a translucent object has a fainter shadow than that of a shadow formed using an opaque object.
        
        However, the shape of the shadow can change if light is shone at different parts of an object.
      - The size of a shadow changes when
        
        The distance between the object and the light source changes.
        
        The shadow of the object becomes bigger when the light source is moved closer to the object.
        
        The distance between the object and the screen changes.
        
        The shadow of the object becomes bigger when the screen is moved further away to the object.
  - - - Food
        
        We need food because food gives us the energy(chemical potential energy) we need for our daily activities such as breathing, moving and growing. When we are more active, we need more energy.
        
        Plants obtain food by making their own. They make it though a process called photosynthesis which requires light, carbon dioxide and water. Sugar(food) and oxygen are produced during photosynthesis. Plants can photosynthesize because they have a green substance called chlorophyll which traps sunlight.
        
        Carbon dioxide is taken in by the plant through tiny openings(stomata) on the leaves.
        
        Sugar is produced in the leaves and transported to other parts of the plant.
        
        Water is absorbed by the roots and transported to the leaves and other parts of the plant.
        
        Oxygen is also produced during photosynthesis. It is given out through tiny openings(stomata) in the leaf.
        
        Light is trapped by the chlorophyll in leaves.