Chapter: 01. Introduction To Chemistry
Exercise For Revision
A. Tick (✓) the correct options.
The systematic knowledge gained by humans through observations and experimentation is called Which of the following is not a branch of Science? The branch of Science that deals with the study of the composition and the physical and chemical properties of various forms of matter is Who created the Periodic Table (of elements)? Which of the following is not the contribution of Antoine Lavoisier to Chemistry? (d) Discovery of radioactivity B. Assertion-Reason based Question.
Assertion: Mendeleev created the periodic table.
Reason: He named the elements carbon, oxygen and hydrogen.
© A is true but R is false. Exercise For Revision
A. Fill in the blanks.
Chemistry helps to increase the production of food. Urea is an important fertiliser. Sodium bisulphite and Benzoic acid are commonly used food preservatives. Antipyretics are used to reduce body temperature. Nylon and polyester are synthetic fibres. B. Assertion-Reason based Questions.
Assertion: The supply of food depends on agriculture.
Reason: Chemistry has helped farmers in increasing the crop production. (a) Both A and R are true and R is the correct explanation of the assertion. Assertion: Excess acid in stomach can cause indigestion.
Reason: It is good to have some mild bases in case of acidity. (b) Both A and R are true but R is not the correct explanation of the assertion. Complete the flowchart for Revision
Central Box: (study of the composition and the physical and chemical properties of matter) Competency Based Discussion: Chemistry and its Importance
Short Answer Questions:
What was the goal of alchemists? Name any two techniques developed by them. The goal of the alchemists was to find a magical substance called the philosopher’s stone, which they believed could turn metals to gold and extend one’s lifespan. Two techniques developed by them are: processes to extract metals from their ores (like isolating zinc and phosphorus) and mixing different metals to form alloys (like making fine quality bronze). What are pesticides? Why do we use them? Pesticides are chemicals used to kill pests. We use them to protect crops from harm caused by pests, which helps to reduce yield loss and increase agricultural production. What are preservatives? State their importance. Preservatives are chemicals used to treat food to prevent the growth of micro-organisms and spoilage of food. Their importance is that they prevent the wastage of food by extending its shelf life. Long Answer Questions:
Write about the contributions of Dmitri Mendeleev and John Dalton to the field of Chemistry. Dmitri Mendeleev: He created the Periodic Table (of elements), arranging the known elements based on their properties. He also predicted the properties of certain elements that were not discovered at that time, providing a systematic way to organize elements and understand their properties. John Dalton: He stated that matter consists of small indivisible particles called atoms. He proposed the atomic theory, which was later called Dalton’s atomic theory, laying a fundamental groundwork for understanding the structure of matter. Briefly discuss the role of Chemistry in agriculture and clothing. Agriculture: Chemistry has significantly helped farmers increase crop production. It provides fertilisers (e.g., urea, sodium nitrate) to supply nutrients to crops and various chemicals like pesticides (e.g., malathion), insecticides (e.g., heptachlor), and fungicides (e.g., Bordeaux mixture) to protect crops from pests, insects, and fungi, thus ensuring higher yields. Clothing: Chemistry has revolutionized the clothing industry by enabling the creation of synthetic fibres. While earlier only natural fibres like cotton and silk were used, Chemistry led to the development of synthetic fibres such as nylon, terylene, polyester, and rayon. These fibres are strong, wrinkle-resistant, and dry quickly, making them highly versatile for various clothing and textile products. Application/Skill-based Questions:
Aditi has made mango jam. She wants to preserve it. Name two chemicals that can be added as preservatives. Benzoic acid and Sodium bisulphite. Ritu is suffering from body pain and fever. Which type of medicine should she take? Ritu should take an Analgesic for body pain and an Antipyretic for fever. 
Answers to textbook exercises