Samacheer Class 6 Science - Chemistry in Everyday Life

The first statement is False because low concentrated phenol is used as a disinfectant, not concentrated phenol. Concentrated phenol is corrosive and harmful. The second statement is False because gypsum is largely used in medical and construction industries, not just medical industries. The third statement is True because plaster of Paris is indeed obtained from heating gypsum at controlled temperatures. The fourth statement is False because adhesives are substances that are used to join two or more components together, not to separate them. Adhesives create bonds between materials. The fifth statement is True because NPK, which stands for Nitrogen, Phosphorus, and Potassium, are the three primary macronutrients that are essential for plant growth and development. These nutrients are required in large quantities by plants for various metabolic processes and are commonly found in fertilizers.

The correct procedure for making soap at home is as follows: First, cover your work area with old newspaper to protect it from spills and stains. Take the necessary quantity of water in a jar. Add concentrated sodium hydroxide to the water carefully and allow the mixture to cool, as this reaction generates heat. Once cooled, add coconut oil drop by drop to the mixture and stir it well continuously to ensure proper mixing and saponification. Continue stirring until the mixture thickens and reaches a soap-like consistency. Pour the resulting solution into an empty matchbox or a mold and allow it to dry completely. Once dried, the solid soap can be removed from the matchbox and used. You can test the soap by using it to wash your handkerchief or other cloth items to verify that it has been properly made and is effective for cleaning.

Phenol properties:
It is a weak acid.
It is a volatile, white crystalline powder.
It is a colourless solution but changes into the red in the presence of dust.

Earthworms take organic wastes as food and produce compost castings.
They provide a multitude of services to improve soil health and consequently plant health.
So earthworm is called a farmer’s friend.

The manufacture of detergents involves several carefully controlled steps using specific materials and processes. The raw materials used include acid slurry, soda ash or sodium carbonate, trisodium phosphate (TSP), sodium tripolyphosphate (STPP), carboxymethyl cellulose, Glauber's salt, colour, perfume, and brightening agents. The manufacturing process begins by neutralizing the acid slurry to reduce its acidity. The neutralized acid slurry is then mixed with soda ash and allowed to react for approximately one hour to ensure complete chemical reaction. After this, other ingredients such as TSP, STPP, carboxymethyl cellulose, Glauber's salt, colour, perfume, and brightener are carefully blended into the neutralized acid slurry with continuous mixing to ensure uniform distribution. The resulting mixture is then dried using appropriate drying equipment to remove moisture. The final product is detergent powder that is ready for packaging and use in cleaning applications.

Make a pit of 30 cm or take a wooden box.
Place a thin net on the base of the pit or wooden box.
Fill it with sand for about 1-2 cm.
Spread some plant wastes (like a dry leaf, flower) and biodegradable wastes on it.
Sprinkle some water.
Add some earthworms to these substances and cover them with an old cloth or dried coconut leaf.
We can find that vermicompost is formed after four weeks.
Use this vermicompost as manure for plants and conserve soil fertility.
Advantages of using vermicompost:
Vermicompost is an excellent organic manure for sustainable agro-practices.
Vermicompost is rich in essential plant nutrients.
In improves soil structure texture, aeration, and water holding capacity and prevents soil erosion.
Vermicompost is rich in nutrients and an eco-friendly amendment to the soil for farming and terrace gardening.
It enhances seed germination and ensures good plant growth.
Vermicompost can be prepared easily.

Detergent molecules have a unique structure with two distinct sides, each with different properties. One side of the detergent molecule is water-loving or hydrophilic, while the other side is water-hating or hydrophobic. When detergent is applied to dirty cloth, the water-hating side of the detergent molecules attaches to dirt, oil, and grease present on the fabric, while the water-loving side remains oriented towards the water. When the cloth is agitated during washing, the detergent molecules surround the dirt particles, with many molecules clustering around each dirt particle. This action lifts and separates the dirt from the cloth surface. The dirt particles, now surrounded by detergent molecules, become suspended in the water and float away, making the water appear dirty. Meanwhile, the cloth becomes clean as the dirt is removed from its surface. This process continues until all the dirt is removed and rinsed away with fresh water.

Inorganic fertilizers supply primary nutrients: Nitrogen (N) — promotes leaf and stem growth and protein synthesis; Phosphorus (P) — aids root development, flowering and energy transfer (ATP); Potassium (K) — regulates water balance, enzyme activation and overall hardiness; Secondary nutrients: Calcium — strengthens cell walls; Magnesium — central component of chlorophyll; Sulfur — needed for some amino acids and proteins; Micronutrients: Iron — required for chlorophyll formation; Zinc — enzyme activation and growth regulation; Copper — involved in respiration and lignin synthesis; Boron — cell wall formation and reproductive development; Manganese — enzyme activation in photosynthesis; Molybdenum — important for nitrogen fixation and nitrate reduction.