O Level – Combined Science

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  • #999

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    O Level Physics/Chemistry Tuition Singapore/Tuition Physics/Chemistry O Level/Tutor

    Please post your Physics and Chemistry Combine Science questions here.

    Thank

    #1249

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    Common Mistakes in O-level Physics
    •Wrong substitutions
    •Answers without appropriate working
    •Missing units
    •Significant figures
    •Vague answers
    •Irrelevant answers

    To excel in O-level Physics, you have to avoid common mistakes make in O-level Physics. Our O-level Physics tutors are able to guide you along to ace in Physics.

    #1509

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    O-Level Singapore/O-Level/Pure Physics Tuition/Physics Tutor

    O-Level Singapore/O-Level Physics Tuition/Physics Tutor

    Measurements – Key Concepts

    1) Metre rule range is several centimetres to one metre, precision 1 mm
    2) Tape measure range is several metres, precision 1 mm
    3) Vernier capilers range between 1 cm to 10 cm, precision 0.1 mm
    4) Micrometer screw gauge < 1 cm, precision 0.01mm

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    #1654

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    Kinematics – Key Concepts

    1. Speed is the distance moved per unit time
    2. Velocity is the change of displacement per unit time
    3. Acceleation is the change of velocity per unit time
    4. The gradient of the tangent at a point on the distance-time graph gives the instantaneous speed
    5. The gradient of the tangent at a point on the speed-time graph gives the instantaneous accleration.
    6. The area under the speed-time graph is the total distance travelled.
    7. When air resistance is negilible, all objects fall under gravity with a constant accleration 10 ms-2
    8. When there is air resistance, falling object will experiences deceleration until it reaches a terminal velocity. This happens when the weight of the object is equal to the air resistance

    Chapter 3 – Purification and Separation

    How to determine that a substance is pure?

    If the substance has a fix melting and boiling point, the substance is pure. We can also use chromatography to check for pure substance.

    #1853

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    Elements, Compounds and Mixtures

    An element is a pure substance that cannot be split into two or more simpler substances by physical and chemical processes.
    Example copper and oxygen gas
    Sugar C6H12O6 is not an element

    A compound is a substance which contains two or more elements chemically joined together.
    Example carbon dioxide and water

    A mixture is a combination of two or more substances not chemically joined together.
    Example sand and sodium chloride

    From : O Level Chemistry Tutor

    #2034

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    Mass, Weight and Density – Key Concepts

    1. Mass is a measure of the amount of substances in an object
    2. Inertia is tendency of any object to resist change in its state of rest
    3. Gravitational field is a region in which a mass experiences the gravitational force of attraction.
    4. Weight of the object will change as the gravitational field strength varies in different planets.
    5. W = mg
    6. Density = Mass/Volume

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    #2419

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    Main points of the Kinetics Theory are:

    1. All matter is made up of tiny particles

    2. Particles are in constant, random motion

    3. As the temperature rises, the particles move faster

    4. In solid, the particles are very close and they can only vibrate about fixed positions

    5. In liquid, the particles are closer together, but they have more energy, and they can move about freely

    6. In gas, the particles are far apart, and they move around rapidly in random

    7. All collisions (especially in liquids & gases) are completely elastic. This means that there is no loss of kinetic (movement) energy after each collision

    Cheers!
    O Level Chemistry Tutor

    #2624

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    Energy, Work and Power – Key Concepts

    1 Work done W by a constant force F is given by the product of the force F and the distance s moved in the direction of the force
    ie W = F x s

    2. SI unit for work done is joule – J

    3. No work done when the direction of the applied force and the direction of in which the object moves are perpendicular to one another.

    4. Kinematic energy KE = 1/2 x mass x velocity ^2

    5. Potential energy PE = mass x g x height

    6. Power = work done / time

    From O Level Physics Tutor

    #2654

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    3 Basic steps writing chemical equations

    Step 1 : Write down the chemical formulae of the reactants and products to get the chemical equation.

    Step 2 : Check the number of atoms of each element in the formulae on both sides of the equation are balanced.

    Step 3 : Add the state symbols

    From : O Level Chemistry Tutor

    #2726

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    Temperature – Key Concepts

    1. Temperature is a measure of the degree of ‘hotness’ or ‘coldness’ of a body.

    2. Heat is thermal energy that is being transferred from a region of higher temperature to a region of lower temperature.

    3. A thermometer uses the physical properties of thermometric substances to measure temperature.

    4. A fixed point is a standard degree of hotness or coldness such as the boiling point or melting point of a substance.

    5. Fixed points are used to set up temperature scale.

    From O Level Physics Tutor

    #2780

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    Thermal Properties of Matter – Key Concepts

    1. Internal energy is made up of kinetic energy and potential energy.

    2. An increase in temperature leads to an increase in kinetic energy component of the internal energy.

    3. Heat capacity C is the amount of thermal energy required to raise the temperature of a body by 1 K (or 1 deg C).

    4. Heat capacity depends on the mass and the material of the object.

    5. The specific heat capacity c is defined as the amount of thermal energy required to raise the temperature of 1 kg (unit mass) of a material by 1 K or 1 deg C.

    6 For the same amount of thermal energy supplied, materials of lower specific heat capacity will heat up to a higher temperature than materials with a higher specific heat capacity.

    From O Level Physics Tutor

    #2831

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    Lights – Key Concepts

    Laws of Reflection:
    1st Law of Reflection
    The incident ray, the reflected ray and the normal to the reflecting surface all lie in the same plane.

    2nd Law of Reflection
    The angle of incidence is equal to the angle of reflection

    Characteristics of the image formed by a plane mirror

    The image is of the same size as the object.
    It undergoes lateral inversion.
    It is upright.
    *It is virtual
    *The distance of the image from the mirror is equal to the distance of the object from the mirror.

    Constructing Ray Diagrams

    1. Ray diagrams are used to locate the position of a mirror image.
    2. Some applications of mirrors include the periscope, for observing blind corners and avoiding parallax error on instrument scales.

    Refraction at Plane Surfaces

    Refraction occurs because the speed of light changes when travelling through different optical media.
    The two Laws of Refraction are:
    The incident ray, the normal and the refracted ray all lie in the same plane.
    For two particular media,

    Sin i/ Sin r = Constant

    where i is the angle of incidence in air.
    where r is the angle of refraction in the medium.

    Total Internal Reflection

    Total internal reflection takes place only when light travels from optical denser to a less dense medium.
    The critical angle c is the angle of incidence in the optically denser medium at which the angle of refraction in the less dense medium is 90°.
    The critical angle c is given by Sin c = 1/n

    Converging Lens

    Lenses are used to converge and diverge a beam of light.
    The main features of a thin converging lens are:
    Optical centre C
    Focal point F
    Focal length f
    Principal axis

    From O Level Physics Tutor

    #2904

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    Waves – Key Concepts

    1. Periodic motion is motion that repeats at regular intervals.

    2. One complete periodic motion – from one extreme position to the other extreme position and back – is known as an oscillation or a vibration

    3. Waves transfer energy from one point to another without any part of the medium being transferred.

    4. There are two types of wave motion: transverse and longitudinal
    When the direction of vibrations is perpendicular to the direction in which the wave moves, the wave is a transverse wave. For example: water waves, light waves.

    5. When the direction of vibrations is parallel to the direction in which the wave moves, the wave is longitudinal. For example: sound waves, pushing and pulling of a Slinky®

    6. Crests and troughs: These are the high points and low points that characterise transverse waves only. For longitudinal waves, the terms compressions and rarefactions are used.

    7. Amplitude (A): The amplitude of one oscillation is the amplitude of the wave. It is half the vertical distance between a wave crest and a wave trough. Its SI unit is the metre (m).

    8. Wavelength (λ): This is the shortest distance between any two points (such as two successive crests or troughs) on a wave that are in phase. Its SI unit is the metre (m).

    9. Period (T): the period of one oscillation is the period of one wave. It is the time taken for a wave crest to move through a distance equal to its wavelength.

    10. Frequency (ƒ): This is the number of complete waves produced per second. Its SI unit is the Hertz (Hz). Frequency and period is related by the equation: ƒ=1∕T

    11. Wave speed (v): This is the distance travelled by a wave in one second. Its SI unit is metres per second (m s-1). The speed of a wave can be computed by the equation: v = ƒλ

    12.Wavefront: A wavefront is an imaginary line on a wave that joins all points which are in the same phase of vibration.

    From O Level Physics Tutor

    #2958

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    Electromagnetic Waves

    Some useful applications of electromagnetic waves include:

    (a) Gamma-rays in radiation therapy (or cancer treatment)
    (b) X-rays in medical (X-ray images) and everyday applications (X-ray scanners)
    (c) Ultraviolet radiation in sunbeds and sterilisation of medical equipment
    (d) Visible light in optical fibres for medical uses and telecommunications
    (e) Infrared radiation in remote controllers and intruder alarms
    (f) Microwaves in microwave ovens and satellite television
    (g) Radio waves in radio and television communications

    From O Level Physics Tutor

    #2971

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    Electromagnetic Waves – Key Concepts

    1. Some useful applications of electromagnetic waves include:

    (a) Gramma-rays in radiation therapy (or cancer treatment)
    (b) X-rays in medical (X-ray images) and everyday applications (X-ray scanners)
    (c) Ultraviolet radiation in sunbeds and sterilisation of medical equipment
    (d) Visible light in optical fibres for medical uses and telecommunications
    (e) Infrared radiation in remote controllers and intruder alarms
    (f) Microwaves in microwave ovens and satellite television
    (g) Radio waves in radio and television communications

    2. Some effects of absorption of electromagnetic waves by humans include:

    (a) Infrared heating
    (b) Damage to different tissues and organs of the human body due to ionising radiation

    From O level Physics Tutor

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