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Subject:

science-chemistry

Class:

class VII

Key Concepts

acids, bases, indicator, neutralization, salt, basic, acidic, reactions

essential questions

1. How does our understanding of the properties of acids and bases help us in our everyday lives?
2. How can we tell if a solution is an acid or base?
3. What happens when acids and bases react?
4. How do we determine if common household substances are acids, bases or neutral?

Remembering:

  1. Identify the acids present in tamarind a) Tannic acid  b) lactic acid  c) citric acid  d) tartaric acid
  2. Which acid is present in vinegar? a) formic acid  b) acetic acid   c) citric acid  d) malic acid
  3. In which of the following is ascorbic acid present? a) tea and coffee  b) milk  c) ants  d) fruts and vegetables
  4. From which of the following is the natural indicator litmus extracted: a) mycorrhiza  b) lichens  c) mucor  d) mycelia
  5. Which of the following is an antacid? a) Mg (OH)2    b) Na OH   c) H2 SO4  d) H2O
  6.  A substance X is found in milk of magnesia. What is X? a) an acid  b) a base  c) water  d) a salt
  7. Identify the base used in making antacid: a) calcium hydroxide  b) sodium hydroxide  c) magnesium hydroxide  d) barium hydroxide
  8. Chemically identify which of the following is baking soda: a) Ca(OH)2    b) NaHCO3  c) NA2 CO3  d) CaO
  9. The effect of sting of an ant can be neutralized be rubbing with ______ a) calcium carbonate  b) sodium carbonate  c) sodium hydrogen carbonate  d) Calcium chloride
  10. The sting of ant contains____ a) Hydrochloric acid   b) Formic acid  c) sulphuric acid   d) ethanoic acid
  11. Find the natural indicator: a) china rose  b) vinegar  c) Phenolphthalein  d) Methyl orange
  12. The solution which do not change the color of either red or blue litmus is known as: a) acid solution  b) base solution  c) Neutral solution  d) indicator

understanding:

  1. What is injected into the skin when an ant bites? a) acids  b) base  c) salt  d) water
  2. Which of the following chemicals are used to neutralize the basic nature of soil a) quick lime  b) organic matter c) slaked lime  d) baking soda
  3. Which of the following is correct statement: a) Acids turn blue litmus to red.  b) Bases turn red litmus to blue  c) Water changes the color of a litmus  d) Both A and B
  4.  What color  does methyl orange indicator change  in the presence of bases: a) green  b) black  c) red  d) yellow
  5. What color does methyl orange indicator change  in the presence of acids: a) green b) black  c) red  d) yellow
  6. What happens when an acid is slowly added to water? a) it release heat   b) it absorbs heat   c) no heat change  d) undergoes neutralization
  7. What changes does colorless phenolphthalein undergo in acid and neutral solution: a) remains colorless  b) turns pink  c) tunrs red  d) turns green
  8.  How does colorless phenolphthalein undergo changes in the presence of bases: a) remains colorless  b) become pink  c) becomes red  d) green
  9. When CO2 is passed through lime water it turns milky. Identify the cause for the milkiness. a) formation of CaCO3  b) formation of Ca(OH)2  c) Formation of H2O  d)Formation of H2

Application:

  1. What will be the effect when phenolphthalien is added to soap solution: a) turns pink  b) remains colourless  c) turns blue  d) turns red
  2.  An indicator is prepared using haldi and added to a solution X. It changes its color to brick red. What is X? a) acidic in nature  b) basic in nature  c) neutral in nature
  3. A type of salt and water were released when X and Y were added together. What is X and Y? a) acidic and acidic   b) acidic and base  c) base and indicator  d) acid and indicator

Analysis:

Evaluation:

Examine two statements carefully and decide if the Assertion A and Reason R are individually true and if so whether the reason is a correct explanation of the assertion.

  1. Assertion A: Organic manure releases acids which neutralizes the basic nature of soil. Reason R: Organic manure contains plant tissues which are made up of proteins.  a) Both A and R are true and R is the correct explanation of A.  b) Both A and R are true but R is not the correct explanation of A.  c) A is true but R is false  d) A is false but R is true.
  2.  Assertion A: Litmus is a commonly used natural indicator . Reason R:Litmus is extracted from lichens which are parasites and dependent on algae for their nutrition. a) Both A and R are true and R is the correct explanation of A.  b) Both A and R are true but R is not the correct explanation of A.  c) A is true but R is false  d) A is false but R is true.
  3. Assertion A: Ant bite on skin causes burning sensation. Reason R: Human blood is alkaline in nature therefore the liquid injected by ant bite release heat inside the blood. a) Both A and R are true and R is the correct explanation of A.  b) Both A and R are true but R is not the correct explanation of A.  c) A is true but R is false  d) A is false but R is true.
  4. Assertion A: Spinach liquid when brought in contact with litmus test, it turned litmus solution to red. Reason R: Spinach has ascorbic acid in it. a) Both A and R are true and R is the correct explanation of A.  b) Both A and R are true but R is not the correct explanation of A.  c) A is true but R is false  d) A is false but R is true.

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