Classification of Materials

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  • We can categorize objects into sets based on their common characteristics
  • To classify objects, the steps are as follows:
  1. Look for similarities or differences
  2. Place object with similar characteristics in a group
  3. Name the group
  • Advantages of classification
  1. To locate objects more easily
  2. To be more systematic and organised

A) Physical Properties of Materials

  • Physical properties are quantities which can be measured by instruments
  • We can also observe or sense these properties by our five senses

B) Types of Materials

  • Materials are substances that can be used to make or create useful things
  • Materials can exist naturally such as metals or man-made such as plastics
  • The common materials that can be classified into ceramics, plastics, fibres, metals and glass.

C) Application of Materials

  • Materials can be used to make different objects
  • The choice of material used to make objects must be based on their suitable physical properties.

Classification of Materials (Worksheet 1)

1. Which of the following physical properties best explains why a balloon is filled with helium gas instead of air?

    A. Has attractive colour

    B. High compressibility

    C. Take on shape of the balloon

    D. Low density

    2. The diagrams below shows four different materials with a same load placing on it. Which of the following depicts a material with the highest flexibility?

    3. A plate is used to prevent the surface of an object from becoming hot. Which substance is least likely to be the choice of the plate and why?

    4. Which of the following reasons best explains why glass is used for light bulbs?

    A. It has a high melting point

    B. It is transparent

    C. It has high strength

    D. It is a good conductor of electricity

    5. The table below shows the scale of hardness of five different substances.

    The harder the substance, the higher the hardness value. Which statement is not true?

    A. Y is able to scratch three substances

    B. W is unable to scratch all the other substances in the scale

    C. V is able to scratch W but not Z

    D. X is able to scratch Y

    6. Which of the following physical properties is suitable for making volleyballs?

    A. High density

    B. Good conductor of heat

    C. Low compressibility

    D. Malleable

    7. Which of the following substances has the highest melting point?

    A. Margarine

    B. Mercury

    C. Wax

    D. Iron

    8. Which of the following reasons are correct for the classification of materials?

    I. Materials with different physical states cannot be classified together

    II. Materials with similar physical states are group together

    III. The study of materials can be done in a more systematic way.

    A. I, II

    B. I, III

    C. II, III

    D. All of the above

    9. Which reason best explains why alminium is used for making drink cans instead of zinc?

    A. It is a good conductor of electricity

    B. It is malleable

    C. It is light

    D. It is a good thermal conductor

    10. The handle of a cooking pan is made of plastics. Which reason best explains why it is made of plastics?

    A. It has a high melting point

    B. It is a poor conductor of electricity

    C. It is a poor conductor of heat

    D. It is light

    11. The table shows the properties of four different materials.

    Which material is possibly a metal?

    12. Which of the following characteristics is not correct about a flower pot made of ceramics?

    A. It is brittle

    B. It is transparent

    C. It is a poor conductor of electricity

    D. It has a low solubility in water

    13. Which of the following applications does not dxepend on the thermal conductivity for its use?

    A. Bimetallic strip in fire alarm

    B. Thermostat in oven

    C. Mercury-in-glass thermometer

    D. Copper wiring in electrical circuits

    14. Mercury and iron are both classified as metals. At room temperature, mercury is a liquid and iron is a solid. Which of the statements is not correct?

    A. Both are good electrical conductors

    B. Both are good thermal conductors

    C. both have the same melting points

    D. Both have a shiny appearance

    15. Tyres are made of _________ as it is ___________ and can withstand high temperature and friction

    A. plastic; less dense than water

    B. metal; malleable

    C. rubber; elastic

    D. metal; malleable

    16. The scale below shows the hardness value of five substances, P to T.

    Which of the following statements is correct?

    A. The scale shows the ability of a material to withstand heavy load without breaking.

    B. Material Q causes scratches on material P when both accidentally touch each other.

    C. Material T can withstand the highest heavy load placed on it.

    D. Material R can be used to cut through material S.

    17. Which property is the reason why tungsten is a suitable material for a filament in a light bulb?

    A. Flexibility

    B. Hardness

    C. Melting point

    D. Strength

    18. A chair is generally made of plastics instead of glass. Which statement best explains why plastics are chosen over glass for this application?

    A. Plastics are poorer heat conductors then glass so that the person does not feel cold when sitting on it.

    B. Plastics have better flexibility than glass so that it allows bending caused by different weights of users sitting on it.

    C. Plastics are more transparent than glass so that the appearance of the chair will be more attractive.

    D. Plastics are harder than glass so that it will not be scratched easily.

    19. Which property is not the reason why copper is a suitable material for wiring electrical circuits?

    A. Malleble

    B. Good heat conductivity

    C. High melting point

    D. Good electrical conductivity

    20. The picture below shows a drill, with a diamond on the tip of the drill bit.

    Which of the following physical properties explain why diamonds are used in drill bits.

    A. Flexibility

    B. Strength

    C. Hardness

    D. Density

    21. In mining fields, drills arfe used to remove rocks to search for the valuable metal ores below.

    The intense drilling generates high amount of frictional heat.

    Which physical properties should be considered when we choose a material to make the drills?

    A. Strength, melting point, transparency

    B. Strength, electrical conductivity, thermal conductivity

    C. Hardness, strength, melting point

    D. Hardness, electrical conductivity, boiling point

    Section B: Short Answer Questions

    1. (a) What is meant by the strength of a substance?

    (b) Why is the strength of material important to the structure of a bridge?

    2. The picture shows the physical appearance of a cooking pan

    Refer to the picture, complete the following table.

    3. Which physical property is the most suitable for making following applications? Explain your choice of answer.

    (a) A table.

    (b) Electrical wiring

    (c) Window panes

    (d) Kettles

    (e) Elastic bands for exercise

    4. State the material that you will use to make the following objects.

    Explain your choice of materials based on the physical properties of the material.

    (a) Gloves for working with electrical circuit.

    (b) Cutting blades of a knife.

    5. The figure below shows the Moh’s scale of hardness which is used to compare the hardness of minerals from talc to a diamond.

    (a) The fingernail can easily scratch some of these minerals. State these minerals.

    (b) A mineral will scratch a copper coin but will not scratch an iron nail. State the mineral

    (c) An unknown mineral can scratch all the common objects listed in the chart. The mineral has the hardness of at least ______ on the scale.

    (d) State one use of the mineral listed in (c)

    6. The picture below shows part of a crane. A rope is used in the crane to lift a heavy object.

    The physical properties of a material is very important because they affect how a material is chosen to make certain useful applications.

    (a) Explain what is meant by physical properties.

    (b) Suggest the appropriate materials A and B used in this crane. Give two reasons g to your answer.

    (i) Material A:

    Reasons:

    (ii) Material B:

    Reasons:

    Section C: Short Answer Questions

    1. (a) What is meant by the hardness of a substance?

    (b) Is hardness equivalent to strength in a material? Explain your answer by using one specific example.

    Worksheet 1 – Classification of Materials

    1. D (Helium has lower density than air)
    2. B (Able to bend without breaking)
    3. A (iron is a good conductor of heat)
    4. B
    5. D (X is less hard than Y)
    6. C
    7. D (iron is a metal)
    8. C
    9. C
    10. C
    11. D (low density, good electrical conductivity and shiny)
    12. B
    13. D
    14. C (Mercury has a lower melting point)
    15. C
    16. B
    17. C
    18. B
    19. B (not required for ALL electrical circuits)
    20. C
    21. C

    Section B

    1. Answer

    (a) Strength is the ability of a substance to support a heavy load without breaking.

    (b) The bridge needs to withstand very heavy loads from the weight of many vehicles without breaking.

    2. Answer

    3. Answer

    (a) High strength to withstand the weights of items put on the table.

    (b) High electrical conductivity so that electricity can pass through easily.

    (c) Transparent so that we can see through it.

    (d) Good conductor of heat so as to boil water quickly.

    (e) Elastic and flexible so that it can be stretched.

    4. Answer

    (a) Rubber/cotton/fabric/wool –> It is a poor conductor of electricity

    (b) Metal/Ceramic –> It is hard (and strong)

    5. Answer

    (a) Gypsum and talc

    (b) Fluorite

    (c) 10 or 11

    (d) It can be used as a cutting tool due to its hardness

    6. Answer

    (a) Physical properties are properties which can be measured by instrumental devices (like thermometer, scale or direct measurement) or detected by our five senses.

    (b) Fibre/plastics (ropes). They are light and strong. They do not break easily when a heavy load is added to it.

    (c) Metals. Metals are strong and hard. They can withstand the heavy loads and can withstand the elements.

    Section C

    1. Answer

    (a) Hardness indicates the ability of a substance to withstand wear-and-tear and scratches.

    (b) They are not the same. The hardness of glass is high as it can scratch objects like wood, plastics or even metals. However, it is not strong as a heavy object placed on glass may break the glass. This indicates that glass is hard but does not have the strength to support heavy objects.

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