Questions: Elements, compounds and mixtures
Nature of Matter: Elements, Compounds, and Mixtures18 min readLesson 5 of 5
Q1. What is a mixture? Explain with two examples and name its components.
Answer (English): A mixture forms when two or more substances are combined and each keeps its own properties. The individual substances in the mixture are called its components, and they do not combine chemically. Poha is a mixture of rice flakes, vegetables and spices, and sugar water is a mixture of sugar and water. In both cases, the components can be identified, and in sugar water they are evenly distributed.
Hinglish: Mixture tab banti hai jab do ya zyada substances milte hain aur har substance apni properties rakhta hai. Mixture ke individual substances ko components kehte hain, aur woh aapas mein chemical reaction nahi karte. Poha mein chawal ke flakes, sabziyan aur masale hain; sugar water mein sugar aur paani. Components ko pehchana ja sakta hai, aur sugar water mein woh evenly distributed hote hain.
Q2. Differentiate between uniform and non-uniform mixtures with two examples of each.
Answer (English): In a uniform mixture the parts are spread evenly and cannot be told apart, even with a microscope. Sugar dissolved in water and air are examples. In a non-uniform mixture the components are visible or can be seen with a magnifying device, so the material does not look the same throughout. Sprout salad and sand mixed with water are examples. The difference is not about how many components there are, but about whether they can be distinguished.
Hinglish: Uniform mixture mein components evenly distributed hote hain aur microscope se bhi alag nahi dikhte, jaise sugar water aur air. Non-uniform mixture mein components dikhte hain ya magnifying glass se dikhte hain, isliye material har jagah same nahi lagta, jaise sprout salad aur sand-water. Farak components ki sankhya ka nahi, unke pehchane jaane ka hai.
Q3. Why is air a mixture? How can the presence of carbon dioxide in air be shown?
Answer (English): Air is a uniform blend of gases: nitrogen, oxygen, argon and carbon dioxide, plus water vapour and traces of other gases. The components are not chemically combined and can be separated, so air is a mixture rather than a compound. To show carbon dioxide, calcium oxide is added to water to make calcium hydroxide, whose clear solution is lime water. When carbon dioxide from the air reacts with this solution, white insoluble particles of calcium carbonate form and the lime water turns milky.
Hinglish: Air uniform mixture hai: nitrogen, oxygen, argon, carbon dioxide, water vapour aur kuch doosri gases ka. Components chemically combined nahi hain aur alag kiye ja sakte hain, isliye air compound nahi mixture hai. Carbon dioxide dikhane ke liye calcium oxide ko paani mein milakar calcium hydroxide banta hai, jiska clear solution lime water hota hai. Hawa ki CO2 se reaction par calcium carbonate ke white particles bante hain aur lime water milky ho jaata hai.
Q4. What does pure mean in science, and how is it different from everyday usage?
Answer (English): In everyday usage, pure means unadulterated, with nothing cheap or of poor quality added. In science, a pure substance contains nothing else: one kind of particle makes up the whole material, and no physical process can split it into different kinds of matter. Everyday products may be called pure but still contain several substances. Milk, for example, contains water, fat, protein and other materials, so in the scientific sense it is a mixture.
Hinglish: Rozmarra mein pure matlab unadulterated, jismein koi sasta ya ghatiya substance nahi milaya gaya. Science mein pure substance mein sirf ek type ke particles hote hain, koi doosra substance nahi, aur ise kisi physical process se alag nahi kiya ja sakta. Kuch products ko pure bola jaata hai par unmein kai substances hote hain. Doodh mein paani, fat, protein wagairah hote hain, isliye science ke hisaab se woh mixture hai.
Q5. What is an element? Explain atoms and molecules with an example.
Answer (English): An element is a pure substance that chemical reactions cannot split into simpler substances. Each element is made of identical particles called atoms, and the atoms of one element are different from those of every other element. Gold, silver, sulfur and carbon are elements. Many atoms do not exist independently: two hydrogen atoms combine to form one hydrogen molecule, and two oxygen atoms form one oxygen molecule.
Hinglish: Element woh pure substance hai jise chemical reaction se simpler substances mein nahi toda ja sakta. Har element identical particles se bana hota hai jinhe atoms kehte hain, aur ek element ke atoms doosre element se alag hote hain. Gold, silver, sulfur aur carbon elements hain. Kai atoms akela nahi rehte: do hydrogen atoms mil kar hydrogen ka ek molecule banate hain, isi tarah do oxygen atoms oxygen molecule.
Q6. What is a compound? Why is water a compound in a fixed ratio?
Answer (English): A compound is a substance formed when different elements combine chemically in a fixed ratio, with properties different from those of the elements that form it. The elements in a compound cannot be separated by physical methods. Water is a compound because hydrogen and oxygen are joined chemically in a fixed ratio of two hydrogen atoms to one oxygen atom. Electrolysis gives hydrogen and oxygen in a volume ratio of about 2:1, matching that fixed composition.
Hinglish: Compound tab banta hai jab different elements fixed ratio mein chemically judte hain aur naye substance ki properties bante hain. Compound ke elements ko physical methods se alag nahi kar sakte. Paani compound hai kyunki hydrogen aur oxygen do hydrogen atoms aur ek oxygen atom ke fixed ratio mein chemically jude hote hain. Electrolysis mein hydrogen aur oxygen kareeb 2:1 volume ratio mein milte hain, jo isi composition se match karta hai.
Q7. Compare the iron-and-sulfur mixture with iron sulfide.
Answer (English): The iron-and-sulfur mixture is non-uniform, with black iron particles and yellow sulfur particles visible. A magnet attracts the iron and can separate it, and dilute hydrochloric acid gives colourless odourless hydrogen that burns with a pop. Heated strongly, the same elements form iron sulfide, a black compound with a uniform texture. A magnet has no effect on iron sulfide, and acid gives hydrogen sulfide, which has a rotten-egg odour. The elements in iron sulfide are joined chemically and cannot be separated by physical means.
Hinglish: Iron aur sulfur ka mixture non-uniform hota hai: black iron aur yellow sulfur particles dikhte hain. Magnet se iron alag ho jaata hai, aur dilute HCl se colourless, odourless hydrogen nikalta hai jo pop sound ke saath jalta hai. Zyada garam karne par wahi elements iron sulfide compound banate hain, jo black aur uniform hota hai. Magnet ka iron sulfide par koi asar nahi, aur acid se rotten-egg smell wali hydrogen sulfide gas nikalta hai. Elements chemically jude hain, physical tarike se alag nahi ho sakte.
Q8. Differentiate between a mixture and a compound.
Answer (English): In a mixture, two or more substances are combined without a chemical reaction, each keeps its own properties, and the components can be separated by physical means. The components may be present in any proportion. In a compound, different elements combine chemically in a fixed ratio, the compound has new properties, and it cannot be separated into its elements by physical means. A magnet can separate iron from a mixture of iron and sulfur, but it cannot separate the iron and sulfur in the compound iron sulfide.
Hinglish: Mixture mein substances bina chemical reaction ke milte hain, har component apni properties rakhta hai, aur unhe physical tarike se alag kiya ja sakta hai; proportion koi bhi ho sakta hai. Compound mein elements fixed ratio mein chemically judte hain, naye properties aate hain, aur compound ko physical methods se elements mein nahi toda ja sakta. Iron-sulfur mixture se magnet iron alag kar sakta hai, par iron sulfide compound se iron aur sulfur alag nahi kar sakta.
Q9. What are minerals and native minerals?
Answer (English): Most rocks are mixtures of minerals, which are natural solids with a fixed chemical composition, found in the Earth. Most minerals are compounds of more than one element, such as quartz, calcite, mica, pyroxene and olivine. Native minerals are pure elements found in nature, such as gold, silver and copper, or non-metals like sulfur and carbon. Useful materials come from minerals: cement comes from calcite, quartz, alumina and iron oxide, and talcum powder from talc.
Hinglish: Zyadatar rocks minerals ka mixture hote hain. Minerals zameen par milne wale natural solid substances hain jinki chemical composition fixed hoti hai. Zyadatar minerals do ya zyada elements ke compounds hote hain, jaise quartz, calcite, mica, pyroxene aur olivine. Native minerals pure elements hote hain jo nature mein milte hain, jaise gold, silver, copper, ya sulfur aur carbon. Cement calcite, quartz, alumina aur iron oxide se banta hai, aur talcum powder talc se.
Q10. How are elements, compounds and mixtures used in daily life? Give three examples.
Answer (English): Elements such as iron and aluminium are used to build bridges, buildings and vehicles, and air, a mixture of gases, is what we breathe. Water, a compound of hydrogen and oxygen, is essential for life, and compounds made by chemists are used in medicines, vaccines and fertilisers. Engineers use mixtures including stainless steel, wood and concrete to build stronger and more durable structures, and the Dhokra art of Bihar and Odisha uses molten brass or bronze to make figures.
Hinglish: Elements jaise iron aur aluminium bridges, buildings aur vehicles mein use hote hain, aur air gases ka mixture hai jo hum saans lete hain. Paani hydrogen aur oxygen ka compound hai aur life ke liye zaroori hai; chemists ke banaye compounds dawaai, vaccine aur fertilisers mein use hote hain. Engineers stainless steel, wood aur concrete jaise mixtures se mazboot structures banate hain, aur Bihar-Odisha ki Dhokra art mein molten brass/bronze se figures banaye jaate hain.
The quick check below has five multiple choice questions on mixtures, elements, compounds and minerals. Each one comes with a short explanation, so take the quiz and see which topics need another read.