Nature of Matter: Elements, Compounds, and Mixtures
Short Questions
1. What is a mixture?
Answer:- A mixture is when two or more substances are mixed but keep their own properties.
2.Name two examples of non-uniform mixtures.
Answer:- Sprout salad and muddy water.
3.What is a uniform mixture?
Answer:- A mixture where components are evenly mixed and cannot be seen separately.
4.Give an example of a uniform mixture.
Answer:- Sugar dissolved in water.
5.What is an alloy?
Answer:- An alloy is a uniform mixture of two or more metals, like brass or bronze.
6.Is air a mixture or a pure substance?
Answer:- Air is a mixture.
7.What gas in air turns lime water milky?
Answer:- Carbon dioxide.
8.What is a pure substance?
Answer:- A substance with only one type of particle.
9.Name two pure substances.
Answer:- Sugar and oxygen.
10.What is an element?
Answer:- An element is a pure substance that cannot be broken down into simpler substances.
11.Give two examples of elements.
Answer:- Iron and oxygen.
12.What is a compound?
Answer:- A compound is a pure substance made of two or more elements chemically combined.
13.Name a compound formed from hydrogen and oxygen.
Answer:- Water.
14.What happens when iron filings and sulfur powder are heated?
Answer:- They form a compound called iron sulfide.
15.What is a mineral?
Answer:- A mineral is a natural, solid substance with a fixed chemical composition.
Long Questions
1. What is the difference between a mixture and a compound?
Answer:- A mixture is made by physically mixing substances that keep their properties. A compound is formed by chemically combining elements, creating a new substance with different properties.
2.Why is stainless steel considered an alloy?
Answer:- Stainless steel is a uniform mixture of iron, nickel, chromium, and carbon. It appears the same throughout and has properties different from its individual metals.
3.How can you prove that air contains carbon dioxide?
Answer:- When lime water is exposed to air, it turns milky due to carbon dioxide reacting with calcium hydroxide. This forms calcium carbonate, confirming carbon dioxide’s presence.
4.What happens when water is broken down by electricity?
Answer:- Water breaks down into hydrogen and oxygen gases through a chemical change. These gases can be identified by a pop sound for hydrogen and a brighter flame for oxygen.
5.Why can’t the components of a compound be separated by physical methods?
Answer:- In a compound, elements are chemically bonded in a fixed ratio. Physical methods like filtration or evaporation cannot break these chemical bonds.
6.How do you know if a mixture is uniform or non-uniform?
Answer:- Uniform mixtures, like sugar in water, have components evenly distributed and invisible separately. Non-uniform mixtures, like sprout salad, have visible, unevenly mixed components.
7. What is the difference between an element and a compound?
Answer:- An element is a pure substance made of one type of atom, like oxygen. A compound is made of two or more elements chemically combined, like water.
8.How does the magnet test help distinguish between a mixture and a compound of iron and sulfur?
Answer:- In a mixture of iron and sulfur, a magnet attracts iron filings, separating them. In the compound iron sulfide, the magnet has no effect because the substances are chemically combined.
9. Why is water considered a compound and not a mixture?
Answer:- Water is made of hydrogen and oxygen chemically bonded in a fixed ratio. Its properties are different from hydrogen and oxygen, unlike a mixture where properties are retained.
10.What are minerals, and how are they used in everyday life?
Answer:- Minerals are natural solids with a fixed composition, like quartz or calcite. They are used in products like cement, talcum powder, and metals for construction or art.
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