CBSE Class 6 Science
Chapter 4: Sorting Materials into Groups
Chapter Summary
- Objects Around Us: Everything around us, like chairs, books, clothes, and food, are called objects.
- Variety of Materials: These objects are made of different materials. For example, a chair can be made of wood, plastic, metal, or a combination.
- Single or Multiple Materials: An object can be made of a single type of material (e.g., a glass tumbler) or from many materials (e.g., a pen made of plastic and metal).
- One Material, Many Objects: The same material can be used to make many different objects. For instance, wood can be used to make chairs, tables, doors, beds, etc.
- Grouping Materials: We group materials based on their similarities and differences in properties. This helps us to study their properties easily and for convenience in everyday life.
- Properties of Materials: Materials have various properties that help us to sort them. Some key properties are:
- Appearance: Materials can look different from each other. Some materials have a shiny appearance, called lustre (e.g., metals like iron, copper, gold). Other materials, like wood or plastic, do not shine. Freshly cut surfaces of metals usually show lustre.
- Hardness: Some materials are hard (difficult to compress) while others are soft (can be easily compressed or scratched). For example, a stone is hard, while cotton is soft.
- Solubility:
- Soluble: Materials that completely disappear or dissolve in water are called soluble substances (e.g., sugar, salt).
- Insoluble: Materials that do not mix with water and remain visible are called insoluble substances (e.g., sand, chalk powder).
- Some liquids mix well with water (e.g., vinegar, lemon juice), while others do not and form separate layers (e.g., oil, kerosene).
- Some gases are soluble in water (e.g., oxygen), while others are not.
- Float or Sink: Some objects float on water (e.g., wood, dry leaves, plastic), while others sink to the bottom (e.g., stone, coin, iron nail). This property depends on their density.
- Transparency: This property describes whether light can pass through a material.
- Transparent: Materials through which objects can be seen clearly are called transparent (e.g., glass, clear water, air).
- Translucent: Materials through which objects are visible, but not clearly, are called translucent (e.g., frosted glass, butter paper).
- Opaque: Materials through which you cannot see at all are called opaque (e.g., wood, cardboard, metal, stone).
- Reasons for Grouping: We group materials for convenience and to study their properties. Knowing the properties helps us choose the right material for a particular purpose (e.g., we don't make tumblers out of cloth because it can't hold liquid).
Questions and Answers
1. Name five objects which can be made from wood.
Answer: Five objects which can be made from wood are:
- Chair
- Table
- Door
- Bed
- Boat
2. Select those objects from the following which shine: Glass bowl, plastic toy, steel spoon, cotton shirt.
Answer: The objects that shine are:
- Glass bowl
- Steel spoon
3. Match the objects given below with the materials from which they could be made. Remember, an object could be made from more than one material and a given material could be used for making many objects.
| Objects | Materials |
|---|---|
| Book | Paper |
| Tumbler | Glass, Plastic, Metal |
| Chair | Wood, Plastic, Metal |
| Toy | Plastic, Wood, Metal |
| Shoes | Leather, Plastic, Cotton, Rubber |
4. State whether the statements given below are ‘True’ or ‘False’.
- (a) Stone is transparent, while glass is opaque.
- (b) A notebook has lustre while eraser does not.
- (c) Chalk dissolves in water.
- (d) A piece of wood floats on water.
- (e) Sugar does not dissolve in water.
- (f) Oil mixes with water.
- (g) Sand settles down in water.
- (h) Vinegar dissolves in water.
Answer:
- (a) Stone is transparent, while glass is opaque. - False (Stone is opaque, glass is transparent).
- (b) A notebook has lustre while eraser does not. - False (Neither notebook nor eraser usually has lustre).
- (c) Chalk dissolves in water. - False (Chalk is insoluble in water; it forms a suspension).
- (d) A piece of wood floats on water. - True
- (e) Sugar does not dissolve in water. - False (Sugar is soluble in water).
- (f) Oil mixes with water. - False (Oil does not mix with water; it forms a separate layer).
- (g) Sand settles down in water. - True
- (h) Vinegar dissolves in water. - True
5. Given below are the names of some objects and materials: Water, Basketball, Orange, Sugar, Globe, Apple, Earthen pitcher. Group them as:
- (a) Round shaped and other shapes
- (b) Eatables and non-eatables
Answer:
(a) Round shaped and other shapes:
- Round shaped: Basketball, Orange, Globe, Apple, Earthen pitcher (often round)
- Other shapes: Water, Sugar (crystalline/granular, not a defined shape for a single grain)
(b) Eatables and non-eatables:
- Eatables: Water, Orange, Sugar, Apple
- Non-eatables: Basketball, Globe, Earthen pitcher
6. List all items known to you that float on water. Check and see if they will float on oil or kerosene.
Answer: Items that float on water (examples):
- Wood piece
- Dry leaves
- Plastic bottle
- Thermocol
- Paper
- Feather
7. Find the odd one out from the following:
- (a) Chair, Bed, Table, Baby, Cupboard
- (b) Rose, Jasmine, Boat, Marigold, Lotus
- (c) Aluminium, Iron, Copper, Silver, Sand
- (d) Sugar, Salt, Sand, Copper sulphate
Answer:
- (a) Chair, Bed, Table, Baby, Cupboard - Baby (All others are furniture items; Baby is a living being).
- (b) Rose, Jasmine, Boat, Marigold, Lotus - Boat (All others are flowers; Boat is a means of transport/object).
- (c) Aluminium, Iron, Copper, Silver, Sand - Sand (All others are metals; Sand is a non-metal/material composed of mineral grains).
- (d) Sugar, Salt, Sand, Copper sulphate - Sand (All others are soluble in water; Sand is insoluble in water).
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