if you are looking for Tamil Nadu Board Class 7 Science Chapter 3 Matter Around Us then you are at the right place. Here we are providing solutions as well as additional QA / Important Notes.
Choose the appropriate answer.
Which one of the following is an example for a metal?
a. Iron b. Oxygen c. Helium d. Water
Oxygen, hydrogen, and sulphur are examples for
- metals
- metalloids
- non-metals
- inert gases
Which of the following is a short and scientific way of representing one molecule of an element or compound?
- Mathematical formula
- Chemical formula
- Mathematical symbol
- Chemical symbol
The metal which is liquid at room temperature is
- chlorine
- sulphur
- mercury
- silver
An element which is always lustrous, malleable and ductile is
a. non-metal b. metal c. metalloid d. gas
Fill in the blanks.
- The smallest particle of matter that can exist by itself is……….[ATOM]
- A compound containing one atom of carbon and two atoms of oxygen is………..[Carbon Dioxide CO2]
- ……….. is the only non-metal which conducts electricity.[Graphite]
- Elements are made up of………….kinds of atoms.[One]
- ………of some elements are derived from Latin or Greek names of the elements.[Symbols]
- There are ……….known elements.[118]
- Elements are the……….for of pure substances.[simplest]
- The first letter of an element is always written in ……….letter.[capital]
- Molecule containing more than three atoms are known as………[polyatomic molecules]
- ……….is the most abundant gas in the atmosphere.[Nitrogen]
Analogy.
- Mercury Liquid at room temperature :: Oxygen:……………[Gas at room temperature]
- Non-metal conducting electricity:[GRAPHITE]:: Metal conductingelectricity: Copper
- Elements: Combine to form compounds :: Compounds:…[COMBINE TO FORM MIXTURES]
- Atoms: Fundamental particle of an element::[MOLECULES]: Fundamental particles of a compound.
State true of false. If false, give the correct statement.
- Two different elements may have similar atoms. [False]
- Compounds and elements are pure substances. [True]
- Atoms cannot exist alone. They can only exist as groups called molecules.[False]
- NaCl represents one molecule of sodium chloride.[True]
- Argon is mono atomic gas. [True]
Answer in brief.
Write the chemical formula and name the elements present in the following compounds.
Sodium chloride
Chemical formula: NaCl
Elements present: Sodium (Na) and Chlorine (Cl)
Potassium hydroxide
Chemical formula: KOH
Elements present: Potassium (K), Oxygen (O), and Hydrogen (H)
Carbon dioxide
Chemical formula: CO2
Elements present: Carbon (C) and Oxygen (O)
Calcium oxide
Chemical formula: CaO
Elements present: Calcium (Ca) and Oxygen (O)
Sulphur dioxide
Chemical formula: SO2
Elements present: Sulphur (S) and Oxygen (O)
What do you understand by chemical formula of a compound? What is its significance?
A chemical formula is a symbolic representation of a compound that indicates the types and numbers of atoms present in a single molecule of that compound. It uses element symbols from the periodic table and numerical subscripts to convey this information.
Significance of Chemical Formulas:
- A chemical formula reveals the exact number of atoms of each element in a molecule.
- It uniquely identifies a chemical substance. Different compounds have different chemical formulas
- Chemical formulas are essential in writing and balancing chemical equations
- Knowing the chemical formula can help predict the properties of a compound
Define the following terms with an example for each.
Element
Definition: An element is a pure substance made up of only one type of atom. It cannot be broken down into simpler substances by chemical means.
Example: Hydrogen (H) is an element. It consists of hydrogen atoms only.
Compound
Definition: A compound is a pure substance formed when two or more different elements chemically combine in a fixed ratio. Compounds have properties that are different from those of their constituent elements.
Example: Water (Hâ‚‚O) is a compound composed of two hydrogen atoms and one oxygen atom.
Metal
Definition: Metals are elements that are typically hard, shiny, malleable, ductile, and good conductors of heat and electricity.
Example: Iron (Fe) is a metal. It is hard, shiny, and a good conductor of electricity.
Non-metal
Definition: Non-metals are elements that are generally not shiny, not malleable, not ductile, and poor conductors of heat and electricity.
Example: Sulfur (S) is a non-metal. It is not shiny and is a poor conductor of electricity.
Metalloid
Definition: Metalloids are elements that have properties intermediate between metals and non-metals. They can exhibit characteristics of both classes.
Example: Silicon (Si) is a metalloid. It has a shiny appearance like a metal but is brittle and a semiconductor, which is typical of metalloids.
Write the symbols for the following elements and classify them as solid, liquid and gas. Aluminum, Carbon, Chlorine, Mercury, Hydrogen and Helium
Aluminum (Al)
Symbol: Al
State: Solid
Carbon (C)
Symbol: C
State: Solid
Chlorine (Cl)
Symbol: Cl
State: Gas
Mercury (Hg)
