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Subject:

science-physics

Class:

class VII

Key Concepts

Chemical changes, Physical change, chemical and physical reaction, rusting, galvanization , crystallization

essential questions

1.What are the characteristics of physical and chemical changes?
2. What evidence do each of these changes show to indicate that they have occurred?
3. How does water and air bring in physical and chemical changes in various substances?

Remembering:

  1. A change in which a substance undergoes changes in its physical properties is called: a) Chemical change b) Physical change c) No Change  d) Biological change
  2. Ozone layer protects us from harmful: a) Ultraviolet radiation b) Infrared Rays c) Visible radiation d) heat radiation
  3. The process of depositing a layer of one metal over another metal surface to protect it from rusting is called: a) galvanization b) crystallization c) amalgamating d) neutralization
  4. Metal that is made by mixing iron with carbon, nickel and manganese is called: a) stainless steel b) German Silver c) Nichrome d) Eureka
  5. The process of obtaining Salt by evaporation of sea water is called: a) Crystallization b) Neutralization c) Galvanization d) Amalgamation
  6. When Magnesium ribbon is burnt in candle flame it burns with: a) brilliant red light b) brilliant yellow light c) brilliant white light  d) brilliant green light
  7. Which change can be easily be reversed? a) Chemical Change b) Physical Change c) Both a physical and chemical change d) Neither a physical or chemical change
  8. When a new substance is formed with different properties than the original substance it is called : a) Chemical change b) Physical change c) Freezing d) Boiling point
  9. Which is an example of a physical change? a) Metal rusting b) Silver tarnishing c) Water boiling d) Paper burning
  10. What characteristic best describes what happen during a physical change? a) Composition changes b) Composition stays the same c) Form stays the same d) Mass is lost
  11. Which is an example of chemical change? a) Water freezes b) Wood is cut c) Bread is baked d) Wire is bent
  12. Which is not a clue that could indicate a chemical change? a) Change in color b) Change in shape c) Change in energy d) Change in odor
  13. What property stays the same during physical and chemical changes? a. Density b. Shape c. Mass d. Arrangement of particle
  14. A physical change occurs when… : a) both the appearance of a substance and its identity change. b) the appearance of a substance changes but its identity does not. c) the identity of a substance changes but its appearance does not. d) Neither the appearance of a substance nor its identity changes.

 

understanding:

  1. When carbon di oxide is passed through lime water, then lime water becomes: a) milky b) shiny c) silvery d) golden yellow
  2. When Magnesium ribbon is brunt in oxygen, the product obtained is: a) magnesium chloride b) Magnesium sulphate c) Magnesium oxide  d) Iron chloride
  3. Magnesium hydroxide, obtained when magnesium oxide is dissolved in water is: a) a base b) an acid c) an Indicator d) a dissolving agent
  4. Least intermolecular forces are found in: a) solids b) liquids c) gases d) fluids
  5.  Reactions of ‘exothermic’ are: a) condensation reactions b) endothermic reactions c) reversible reactions d) substitution reactions
  6. Which of the following is an example of physical change? a) Mixing baking soda and vinegar together, and this causes bubbles and foam b) A glass cup falls from the counter and shatters on the ground c)Lighting a piece of paper on fire and the paper burns up and leaves ashes  d) Baking a birthday cake for your mother.
  7. Which of the following is an example of chemical change? a) Filling up a balloon with hot air b)Taking a glass of water and freezing it by placing it in the freezer  c) A plant collecting sunlight and turning it into food d) Your dog ripping up your homework
  8. If the chemical properties of a substance remain unchanged and the appearance or shape of an substance changes it is called : a) Chemical change b) Physical change c) Both a physical and chemical change d) Neither a physical or chemical change
  9. Two solutions are added together and the new solution becomes hot. This tells you that a) a gas is being produced. b) Solutions are not soluble. c) Physical properties are the same. d) chemical change is taking place.
  10. Write 5 differences between chemical and Physical changes.
  11. Write the difference between endothermic and exothermic reactions.

Application:

  1. Brown color of the apple after cutting is: a) physical change b) chemical change c) no change d) biological change
  2. For protecting iron pipes for corrosion, they are coated with: a) zinc b) copper c) aluminium  d) silver
  3. Blue colour of the copper sulphate solution changes to green colour when an iron nail is dropped into it due to the formation: a) iron sulphate b) copper chloride c) copper iron sulphate d) iron chloride
  4. When liquids are heated, they: a) expand more than gases but less than solids b) expand more than solids but less than gases  c) do not expand  d) none of above

Analysis:

  1. A solid brown metal is added to a clear acidic solution. A white powder appears and the acid solution becomes cloudy. Which type(s) of change have/has occurred? a) both chemical and physical b) only physical c) neither chemical nor physical d) only chemical
  2. Which of the following causes a sugar cube to only change physically, not chemically? a) burning the sugar cube with a match b) crushing the sugar cube and dissolving it in water c) dehydrating the sugar cube with sulfuric acid d) chewing the sugar cube and digesting it
  3. Is melting and freezing process a physical or chemical change, can you give reasons to explain your answer?
  4. Is it correct to say burning candle is a chemical and physical change happening simultaneously? Explain in detail.

Evaluation:

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