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Prepared by: learnloophq@gmail.com
Last edited 25 days ago by Learn LoopHQ.

Chapter: 03. Elements And Compounds

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What is the main use of carbon dioxide for plants?
Carbon dioxide is used by plants for the process of photosynthesis, where they make their food.
How many elements have scientists discovered in total?
Scientists have discovered 118 elements.
How do the melting points of diamond and graphite compare to most other non-metals?
Diamond and graphite have very high melting points, which is an exception to the general rule that non-metals have low melting points.
Explain why O_2 and 2O are not the same.
O_2 represents one molecule of oxygen, where two oxygen atoms are chemically bonded, whereas 2O represents two separate, uncombined atoms of oxygen.
What is atomicity?
Atomicity is the number of atoms present in the molecule of an element.
How do impurities affect the boiling and freezing points of a pure substance like water?
When impurities are mixed in a pure substance like water, its boiling point increases and its freezing point decreases.
What is the significance of the Periodic Table?
The Periodic Table is a systematic arrangement of elements in a tabular form that simplifies the study of elements by grouping them based on their properties.
Give one exception to the general rule that metals are solid at room temperature.
Mercury is an exception as it is a liquid metal at room temperature.
Why are metals generally considered good conductors of heat and electricity?
Metals are generally good conductors of heat and electricity due to the presence of free electrons in their structure.
What is the difference in sonorousness between metals and non-metals?
Metals are sonorous, meaning they produce a ringing sound when struck, while non-metals are non-sonorous and do not produce a ringing sound.
What is the chemical formula for common salt?
The chemical formula for common salt (sodium chloride) is NaCl.
What are minerals?
Minerals are the combined forms in which most metals are found on the earth, serving as their main source.
What is the reason behind iron’s use in heavy tools and machines?
Iron is used in heavy tools and machines primarily because of its high mechanical strength.
How is an element defined in chemistry?
An element is a pure substance made up of only one kind of atoms that cannot be split into two or more simpler substances by any physical or chemical method.
What information does the chemical formula H_2O provide?
The chemical formula H_2O indicates that water is composed of hydrogen and oxygen, with two atoms of hydrogen chemically combined with one atom of oxygen in each molecule.
How is a compound formed?
A compound is formed when two or more elements chemically combine in a fixed proportion by mass.
What does it mean for a metal to be malleable?
For a metal to be malleable means it can be hammered into thin sheets or foils without breaking.
Name two non-metals that are gases at room temperature.
Oxygen and nitrogen are two non-metals that are gases at room temperature.
What are metalloids?
Metalloids are elements that exhibit properties intermediate between those of metals and non-metals.
What is the difference between a pure substance and an impure substance?
A pure substance contains only one kind of particles, while an impure substance or mixture contains two or more pure substances physically mixed.
What happens to energy during the formation of a compound?
During the formation of a compound, energy (in the form of heat or light) is either absorbed or released.
How do the properties of a compound compare to its constituent elements?
The physical and chemical properties of a compound are entirely different from the properties of its constituent elements.
Give an example of a noble gas.
Helium is an example of a noble gas.
Provide an example of a diatomic molecule.
Hydrogen (H_2) is an example of a diatomic molecule.
Why are copper and aluminium used in electrical wires?
Copper and aluminium are used in electrical wires because they are excellent conductors of electricity.
Which non-metal is known for being extremely hard?
Diamond, a form of carbon, is an extremely hard non-metal.
What role does iron play in living organisms?
Iron is present in haemoglobin, a respiratory pigment found in the blood of living organisms.
Besides definite chemical composition, what are two other characteristic sensory properties of pure substances?
Pure substances have a characteristic colour, odour, and taste.
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