Class 7 Science Chapter 5 Important Questions
Class 7 Science Chapter 5 Important Questions and Keywords of Acids, Bases and Salts updated for new academic session 2020-21. These important questions class 7 science chapter 5 extra question answers based on notes and exercises.All the question answers are helpful in the preparation of school tests and exams.
Class 7 Science Chapter 5 Important Questions 2020-2021
|Chapter: 5||Acids, Bases and Salts|
|Contents:||Important Extra Questions with Answers|
Class 7 Science Chapter 5 Important Questions Set – 1
What are acids? Write the names of acids which is used by us in our daily life.
Substances which are sour in taste are called acids.
We use in our daily life a large number of acids such as curd, lemon, juice, orange juice, vinegar, tamarind etc. These substances taste sour because they contain acids.
What are bases? Write the names of bases which is used by us in our daily life.
Substance which are bitter in taste and soapy to touch are called bases.
We use in our daily life a large number of bases such as baking soda, washing soda, milk of magnesia, lime water etc. These substances taste bitter because they contain bases.
What is the effect of indicators on acidic, basic and neutral solution?
Methyl orange and phenolphthalein used as indicator. In acidic solution, methyl orange gives red colour but in basic solution it gives yellow colour. In acidic solution, phenolphthalein is colourless but in basic it gives pink colour.
What do you mean by neutral solution?
The solutions which do not change the colour of either red or blue litmus are known as neutral solutions. These substances are neither acidic nor basic.
What do you mean by indicators? Name two naturally occurring indicators.
A special type of substances are used to test whether a substance is acidic or basic. These substances are known as indicators. The indicators change their colour when added to a solution containing an acidic or a basic substance.
Turmeric, litmus, china rose petals (Gudhal), etc., are some of the naturally occurring indicators.
Class 7 Science Chapter 5 Important Questions Set – 2
What is litmus? How is it prepared?
The most commonly used natural indicator is litmus. It is extracted from lichens. It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. It is available in the form of a solution, or in the form of strips of paper, known as litmus paper.
Generally, it is available as red and blue litmus paper.
Give an idea about acid rain.
We get water from rain. It is the pure form of water but the rain containing excess of acids is called acid rain. The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen
dioxide (which are released into the air as pollutants) dissolve in rain drops to form carbonic acid, sulphuric acid and nitric acid respectively. Pollutants present in the atmosphere mix with the rain to make it acidic and it can cause damage to buildings, historical monuments, plants and animals.
What do you mean by indigestion?
Our stomach contains hydrochloric acid. It helps us to digest food. But too much of acid in the stomach causes indigestion. Sometimes indigestion is painful. To relieve indigestion, we take an antacid such as milk of magnesia, which contains magnesium hydroxide. It neutralises the effect of excessive acid.
What is the effect of ant bite? Explain its cure.
When an ant bites, it injects the acidic liquid (formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate.
What do you mean by neutralization reaction? Explain with examples.
When an acidic solution is mixed with a basic solution, both the solutions neutralise the effect of each other. When an acid solution and a base solution are mixed in suitable amounts, both the acidic nature of the acid and the basic nature of the base are destroyed. The resulting solution is neither acidic nor basic. In neutralisation reaction, heat is always produced, or evolved. The evolved heat raises the temperature of the reaction mixture.
In neutralisation reaction a new substance is formed. This is called salt. Salt may be acidic, basic or neutral in nature. The reaction between an acid and a base is known as neutralisation. Salt and water are produced in this process with the evolution of heat. Thus, neutralisation can be defined as follows:
Acid+Base → Salt+Water (Heat is evolved)
The following reaction is an example:
Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) -> Sodium chloride (NaCl) + Water (H2O)
Class 7 Science Chapter 5 Important Questions Set – 3
What do you mean by soil treatment?
When a farmer uses excessive use of chemical fertilisers makes the soil acidic. Plants do not grow well when the soil is either too acidic or too basic. When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide). If the soil is basic, organic matter is added to it. Organic matter releases acids which neutralises the basic nature of the soil.
How can you neutralize the factory waste?
The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances.
Which acid is called “King of chemicals”?
Sulphuric acid is called king of chemicals.
How do you prepare turmeric paper?
Take some turmeric and mix it in some water to make a paste. Deposit it on blotting paper or filter paper and dry it. Cut thin strips of the yellow paper so obtained. These thin strips are turmeric paper.
What do you mean by organic acids and mineral acids? Give examples.
Organic acids are the naturally occurring acids they are found in various types of plants and animals. Some of the important organic acids which occur in nature are acetic acid, formic acid, citric acid, tartaric acid etc.
The acids prepared from the minerals of the earth are called mineral acids. Mineral acids are the man-made acids. Mineral acids are also known as laboratory acids because they are used in the science laboratory to perform experiments. Such as hydrochloric acid, sulphuric acid and nitric acid.
Class 7 Science Chapter 5 Important Questions Set – 4
Write down some strong acids and weak acids name and its uses.
Hydrochloric acid, sulfuric acid and nitric acid are strong acids. On the other hand, acetic acid, formic acid, citric acid, tartaric acid and carbonic acid are some of the weak acids. Hydrochloric acid is used in cleaning kitchen sinks and bathroom sanitaryware. Sulphuric acid is used in making storage batteries for cars, buses, trucks and inverters. Nitric acid is used by goldsmith for cleaning gold and silver ornament.
Being weak organic acids like acetic acid, citric acid and tartaric acid are used as food ingredients. Many foods like pickle and tomato ketchup contains acetic acid in the form of vinegar. Baking powder used in making cakes and biscuits contain tartaric acid. Carbonic acid is used in fizzy soft drinks and soda water. It gives them a pleasant taste.
How acids are different from bases?
A substance which reacts with a base to form a salt and water is called an acid. Acids have sour taste. Acids turn blue litmus to red. Some of the examples, of acids are acetic acid, citric acid, hydrochloric acid, sulphuric acid, nitric acid etc.
A substance which can neutralize an acid to form a salt and water is called a base. Base have bitter taste. Bases turn red litmus to blue. Bases are the chemical opposites of acids. Some of the examples, of bases are sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide. A base which is soluble in water is called an “alkali”.
How can we prevent tooth decay? Discuss.
We know that some of the sugary food eaten by us is converted into acid by the bacteria present in our mouth. And this acid causes tooth decay. The toothpaste which we use for brushing and cleaning our teeth is basic in nature. Since toothpaste is basic, it neutralizes the acid in our mouth and hence prevents tooth decay.
“China rose” and “Turmeric” indicator give which type of colour when it reacts with acids and bases?
Although both are natural indicator. “Acids” turn china rose indicator to magenta (deep pink) and “Bases” turn china rose indicator to green.
In the other hand turmeric paper is yellow in “Acid solution”. “Bases” turn the yellow turmeric paper to red.
Write down the damages occurred by the acid rain?
The rain which contains a higher level of acid than normal is called acid rain.
- Acid rain makes the water of lakes, ponds and rivers too acidic due to which fish and other aquatic animals get killed.
- Acid rain eats up the leaves of the tree gradually. By using leaves, the trees die.
- Acid rain also damages crop plant in the fields.
- Acid rain damages the metal structures like steel bridges etc. when it falls on them.
- Acid rain damages the surface of building and monuments made of stone.
Class 7 Science Chapter 5 Important Questions Set – 5
Is the distilled water acidic/basic/neutral, how would you verify it?
Distilled water is neutral by nature. We can verify it by litmus test. As water does not change the colour of either red or blue litmus.
Boojho has a few bottles of soft drink in his restaurant. But unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Boojho decide which drink is to be served to whom?
Boojho can use litmus test on this drink. Just drop few drops of drink on litmus paper and take the decision according to the following:
If it turns blue drink is basic, if it turns red drink is acidic and if it turns green drink is neutral.
While playing in a park, a child was stung by a wasp. Some elders suggested applying paste of baking soda and others lemon juice as the remedy. Which remedy do you think is appropriate and why?
Wasp stink inject a liquid in the skin which is acidic in nature. Hence, baking soda is the appropriate remedy as it is basic in nature and neutralizes the acid.
Why calamine solution is applied on the skin when an ant bite?
The sting of an ant contains formic acid which causes irritation on the skin. Calamine solution contains, zinc carbonate which is a base. Calamine solution neutralize the acid effect of the ant bite when applied on the skin.
Explain two neutralization reaction related to daily life situations.
Ant bite, when an ant bite injects the acidic liquid (formic acid) into the skin, the effect to the acid can be neutralized by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate.
Indigestion, our stomach contains hydrochloric acid. It helps us to digest food but too much of acid in the stomach causes indigestion. Sometimes, indigestion is painful. To relieve in digestion, we take an antacid such as milk of magnesia which contains magnesium hydroxide. It neutralizes the effect of excessive acid.