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Chemistry · Chapter 1: Introduction to Chemistry
What is Chemistry?
Chemistry is the study of the composition, structure and properties of matter and the changes it undergoes. Definition, chemistry in daily life and why it is the central science.
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01Concept
Chemistry is the branch of science that deals with the composition, structure and properties of matter, and the changes that matter goes through, including the energy given out or taken in during those changes.
In simple words, chemistry asks three questions about any substance:
- What is it made of? Water is made of hydrogen and oxygen.
- How are its particles arranged and joined? In water, each oxygen atom is joined to two hydrogen atoms.
- How does it change? Water boils into steam; iron rusts in damp air.
Chemistry is all around you
| In daily life | The chemistry behind it |
|---|---|
| Cooking roti and making chai | Heat causes chemical changes in flour; sugar dissolves in tea. |
| Washing clothes | Soap and detergent molecules lift oil and dirt into the water. |
| Medicines such as paracetamol | Chemists make and test the medicine so each tablet has the right amount. |
| Urea fertiliser for wheat and cotton | Made from natural gas, air and water in fertiliser factories. |
| Petrol, CNG and LPG | Fuels that release energy when they burn in oxygen. |
| Cement for houses | Made by heating limestone and clay in a kiln. |
Why chemistry is called the central science
Chemistry sits between physics and biology, so other sciences depend on it. Biologists need chemistry to understand digestion and DNA, doctors need it for medicines, geologists for rocks and minerals, and environmental scientists for pollution.
How chemists work
Chemistry is an experimental science. Chemists observe, measure, test ideas with experiments and record results carefully, the same scientific method used in physics and biology.
02Real World Examples
Clean drinking water
Water treatment plants add chlorine to kill germs. Too little is unsafe and too much tastes bad, so chemists measure it carefully.
Rust on iron gates
Near the sea in Karachi, iron gates rust quickly because salty, damp air speeds up the reaction between iron, oxygen and water. Paint stops this.
Mobile phone batteries
A lithium-ion battery stores energy as chemical energy and releases it as electricity.
Fireworks at weddings
The colours come from metal salts: copper compounds give blue-green and strontium compounds give red.
03Practice Questions
Try to answer in your own words first, then open the model answer.
Short questions
Q1.Define chemistry.Show answer
Answer
Chemistry is the branch of science that deals with the composition, structure and properties of matter, and the changes it undergoes, including the energy changes involved.
Q2.Where does the word "chemistry" come from?Show answer
Answer
It comes from alchemy, which comes from the Arabic word al-kimiya.
Q3.Why is chemistry called the central science?Show answer
Answer
Because many other sciences depend on it. Biology uses chemistry to explain digestion and DNA, medicine uses it to make drugs, and geology uses it to study rocks and minerals.
Q4.Give four examples of chemistry in daily life.Show answer
Answer
- Cooking food: chemical changes in flour and meat.
- Soap and detergents for washing.
- Medicines such as paracetamol.
- Fertilisers such as urea for crops.
Long questions
Q5.What is chemistry? Explain its importance in our daily life with examples.Show answer
Answer
Chemistry is the branch of science that deals with the composition, structure and properties of matter, and the changes it undergoes.
- Food: cooking, preserving and adding nutrients to food all use chemistry.
- Health: medicines, vaccines and disinfectants are made and tested by chemists.
- Agriculture: fertilisers such as urea and pesticides help farmers grow more wheat and cotton.
- Cleaning: soaps and detergents remove grease and dirt.
- Energy: petrol, gas and batteries store chemical energy.
- Buildings: cement, glass, steel and paint are products of chemistry.