Acids, bases, and salts are chemical substances with distinct properties. Acids taste sour, while bases taste bitter and feel soapy. Natural indicators like litmus, turmeric, and China rose help identify acidic or basic solutions. Neutralization occurs when acids and bases react, forming salt, water, and heat. This process has practical uses, such as treating indigestion, ant bites, and soil acidity. Acid rain and factory wastes can harm the environment, but neutralization methods help reduce their impact. Get Notes and mind map of this chapter for free.
ACIDS
- Acids taste sour and contain natural acids.
- Examples include lemon juice, orange juice, and vinegar.
- Acids turn blue litmus paper red.
- Acid rain has extra acids from pollutants in rainwater.
- Acid rain can harm buildings, monuments, plants, and animals.
- Laboratory acids can be corrosive, irritating, and harmful to skin.
BASES
- Bases taste bitter and feel soapy.
- Baking soda is an example of a base.
- Bases turn red litmus paper blue.
- Laboratory bases can be corrosive, irritating, and harmful to skin.
INDICATORS OVERVIEW
GENERAL INDICATORS
- Indicators change color to show if something is acidic or basic.
- Examples include litmus, turmeric, and China rose petals.
- Neutral substances do not change red or blue litmus paper.
NEUTRALIZATION BASICS
- Neutralization happens when an acid and a base mix.
- It forms salt and water.
- Heat is produced during neutralization.
NATURAL INDICATORS
LITMUS
- Litmus is a natural dye from lichens.
- In distilled water, litmus is mauve (purple).
- Litmus turns red in acidic solutions and blue in basic solutions.
- Litmus comes as a solution or red and blue litmus paper.
TURMERIC AND CHINA ROSE
- Turmeric is a natural indicator.
- Soap solution turns turmeric stains red because soap is basic.
- China rose petals turn acidic solutions dark pink (magenta) and basic solutions green.
PHENOLPHTHALEIN
- Phenolphthalein is an indicator.
- It turns pink in basic solutions.
- It stays colorless in acidic solutions.
NEUTRALIZATION PROCESS
REACTION DETAILS
- Neutralization occurs when an acid and base mix in the right amounts.
- Heat is always produced, raising the mixture’s temperature.
- A new substance called salt is formed.
- Salts can be acidic, basic, or neutral.
EQUATION AND EXAMPLE
- The general equation is: Acid + Base → Salt + Water + Heat.
- Example: Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H2O).
NEUTRALIZATION IN DAILY LIFE
INDIGESTION AND ANT BITES
- Too much stomach acid (hydrochloric acid) causes indigestion.
- Antacids like milk of magnesia (magnesium hydroxide) neutralize it.
- Ant bites inject formic acid, causing irritation.
- Baking soda or calamine solution neutralizes ant bite acid.
SOIL TREATMENT
- Soil can become acidic from chemical fertilizers.
- Acidic soil is treated with bases like quick lime or slaked lime.
- Basic soil is treated with organic matter (compost).
FACTORY WASTES AND INDICATORS
- Factory wastes with acids are neutralized with bases before release.
- This protects aquatic life in water bodies.
- Phenolphthalein turns pink in basic solutions and colorless in acidic ones.
EVERYDAY APPLICATIONS
HEALTH APPLICATIONS
- Excess stomach acid is neutralized by antacids like milk of magnesia.
- Ant bite acid is neutralized by baking soda or calamine solution.
ENVIRONMENTAL APPLICATIONS
- Acidic soil is balanced with bases like quick lime or slaked lime.
- Basic soil is balanced with organic matter.
- Acidic factory wastes are neutralized to protect water bodies.
NCERT FAQ
- Question: Suppose you are given the choice in winter of using either one thick blanket or two thin blankets joined together. What would you choose and why?
- Answer: Remember that there would be a layer of air in between the blankets. Woollen clothes keep us warm in winter because wool is a poor conductor of heat, and air is trapped in between the wool fibres, preventing heat flow from our body to the cold surroundings.
- Question: Why are you advised to use an umbrella when you go out in the sun?
- Answer: All hot bodies radiate heat. When this heat falls on some object, a part of it is reflected, a part is absorbed and a part may be transmitted. The temperature of the object increases due to the absorbed part of the heat.
- Question: Why is it more comfortable to wear white or light-colored clothes in the summer and dark-colored clothes in the winter?
- Answer: Dark surfaces absorb more heat and, therefore, we feel comfortable with dark colored clothes in the winter. Light coloured clothes reflect most of the heat that falls on them and, therefore, we feel more comfortable wearing them in the summer.
- Question: In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
- Answer: Light colored clothes reflect most of the heat that falls on them and, therefore, we feel more comfortable wearing them in the summer.
- Question: Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
- Answer: Woollen clothes keep us warm in winter In the winter, we use woollen clothes. Wool is a poor conductor of heat. Moreover, there is air trapped in between the wool fibres. This air prevents the flow of heat from our body to the cold surroundings. So, we feel warm.
- Question: One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be…?
- (d) between 30°C and 50°C
- Question: An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will…?
- (b) not flow from iron ball to water or from water to iron ball
- Question: A wooden spoon is dipped in a cup of ice cream. Its other end…?
- (d) does not become cold
- Question: Stainless steel pans are usually provided with copper bottoms. The reason for this could be that…?
- (c) copper is a better conductor of heat than the stainless steel
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