Samacheer Kalvi 7th Science Term 1 Solutions Chapter 3 Pdf
Tamilnadu Board Samacheer Kalvi 7th Science Term 1 Solutions Chapter 3: Tamilnadu State Board Solution Class 7 Science Term 1 Chapter 3 – Matter Around Us.
Samacheer Kalvi 7th Science Term 1 Solutions Chapter 3: Overview
Board |
Samacheer Kalvi |
Class |
7 |
Subject |
Science |
Chapter |
3 |
Chapter Name |
Matter Around Us |
Samacheer Kalvi 7th Science Term 1 Solutions Chapter 3 Pdf
Matter Around Us
Chapter 3
I.) Choose the appropriate answer.
1.) Which one of the following is an example for a metal?
a.) Iron
b.) Oxygen
c.) Helium
d.) Water
Answer : a) Iron
Solution : Metals are hard and shiny elements.
example: silver, copper, iron, gold, aluminium, etc.
2.) Oxygen, hydrogen, and sulphur are examples for
a.) metals
b.) non-metals
c.) metalloids
d.) inert gases
Answer: b. non-metals
Solution: Non-metals are dull and soft.
example: oxygen, hydrogen and chlorine , etc .
3.) Which of the following is a short and scientific way of representing one molecule of an element or compound?
a.) Mathematical formula
b.) Chemical formula
c.) Mathematical symbol
d.) Chemical symbol
Answer: b. Chemical formula
Solution: Water = H2O, Glucose = C6H12O6
4.) The metal which is liquid at room temperature is
a.) chlorine
b). sulphur
c.) mercury
d.) silver
Answer: c. mercury
Solution : Mercury is the only exceptional metal that is liquid at room temperature
5.) An element which is always lustrous, malleable and ductile is
a.) non-metal
b.) metal
c.) metalloid
d.) gas
Answer: b. metal
Solution: Metal are lustrous, malleable and ductile in nature.
II.) Fill in the blanks.
1.) The smallest particle of matter that can exist by itself is atom
2.) A compound containing one atom of carbon and two atoms of oxygen is carbondioxide
3.) Graphite is the only non-metal which conducts electricity.
4.) Elements are made up of same kinds of atoms.
5.) Sodium and Potassium of some elements are derived from Latin or Greek names of the elements.
6.) There are 118 number of known elements.
7.) Elements are the simplest form of pure substances.
8.) The first letter of an element is always written in Capital letter.
9.) Molecule containing more than three atoms are known as polyatomic molecules
10.) Nitrogen is the most abundant gas in the atmosphere.
III.) Analogy
1.) Mercury : Liquid at room temperature :: Oxygen: Gas at room temperature
2.) Non-metal conducting electricity : Graphite :: Metal conducting electricity : Copper
3.) Elements : Combine to form compounds :: Compounds : Can be split into elements
4.) Atoms : Fundamental particle of an element :: Element : Fundamental particles of a compound.
IV.) State true of false. If false, give the correct statement.
1.) Two different elements may have similar atoms.
Answer: false
Solution: Two different elements may have different atoms.
2.) Compounds and elements are pure substances.
Answer: True
3.) Atoms cannot exist alone. They can only exist as groups called molecules.
Answer: false
Solution: Atoms can exist alone.
4.) NaCl represents one molecule of sodium chloride.
Answer: True
5.) Argon is mono atomic gas.
Answer: True
V.) Answer in brief.
1.) Write the chemical formula and name the elements present in the following compounds.
a.) Sodium chloride
b.) Potassium hydroxide
c.) Carbon dioxide
d.) Calcium oxide
e.) Sulphur dioxide
Answer: a) chemical formula – NaCl
Element : Na – sodium, Cl – chloride
b) chemical formula – KOH
Element: K – potassium, OH – Hydroxide
c) chemical formula – CO2
Element : C – carbon, O – oxygen
d) chemical formula – CaO
Element – Ca – calcium, O – oxygen
e) chemical formula – SO2
Element: S – sulphur, O- oxygen
2.) Classify the following molecules as the molecules of element or compound.
1.) O-O 2.) O-C-O 3.) N-N 4.) Na-Cl
Answer: 1 ) oxygen gas 2) Carbon dioxide 3) Nitrogen gas 4) Sodium chloride
3.) What do you understand by chemical formula of a compound? What is its significance?
Answer: A chemical formula is a symbolic representation of one molecule of an element or a compound. It’s significance is that it provides information about the elements present in the molecule and the number of atoms of each element.
4.) Define the following terms with an example for each.
a.) Element
b.) Compound
c.) Metal
d.) Non-metal
e.) Metalloid
Answer: a) Element- Matter in its simplest form is called an element. Ex-magnesium, sodium, hydrogen, chloride etc.
b) Compound – A compound is a pure substance that is formed when the atoms of two or more elements combine chemically in definite proportions. Ex- common salt ,chalk , sugar etc.
c) Metal – A solid material which is hard, shiny, malleable and ductile, with good electrical and heat conductivity. Ex – iron, gold, silver, copper etc.
d) Non Metal- A material which is soft, dull and do not have good electrical and heat conductivity. Ex – iodine , oxygen, nitrogen etc .
e) Metalloid- Metalloids exhibit the properties of both metals and non metals. Silicon, arsenic, antimony, and boron are some examples of metalloids.
5.) Write the symbols for the following elements and classify them as solid, liquid and gas.
Aluminum, Carbon, Chlorine, Mercury,
Hydrogen and Helium
Answer:
Element | Symbol |
Classification |
Aluminum | Al | Solid |
Carbon | C | Solid |
Chlorine | Cl | Gas |
Mercury | Hg | Liquid |
Hydrogen | H | Gas |
Helium | He | Gas |
6.) Classify the following as metals, non-metals and metalloids.
Sodium, Bismuth, Silver, Nitrogen, Silicon, Carbon, Chlorine, Iron, Copper
Answer: 1.) Sodium – Metal
2.) Bismuth- Metal
3.) Silver- Metal
4.) Nitrogen- Non-metal
5.) Silicon – Metalloid
6.) Carbon – Non-metal
7.) Chlorine- Non-metal
8.) Iron – Metal
9.) Copper – Metal
7.) Classify the following as elements and compounds.
Water, Common salt, Sugar, Carbon dioxide, Iodine and Lithium
Answer: Water- Compounds
Common salt – Compounds
Sugar – Compounds
Carbon dioxide – Compounds
lodine – Elements
Lithium – Elements
8.) Write the chemical formula for the following elements.
a.) Hydrogen b. Nitrogen c. Ozone d. Sulphur
Answer: a) H2
b) N2
c) O3
d) S2
9.) What are elements? What are they made of? Give two examples.
Answer: Matter in its simplest form is called an element. Elements are made up of the same types of atoms .Two examples of elements are carbon atom and hydrogen atom.
10.) Define molecule.
Answer: When an atom combines with another atom (or atoms) and forms a compound, it is called as molecule.
11.) What are compounds? Give two examples.
Answer: A compound is a pure substance that is formed when the atoms of two or more elements combine chemically in definite proportions. Ex- 1)common salt (Sodium chloride) , 2)Chalk (Calcium, Carbon and Oxygen) etc.
12.) Give an example for the elements derived from their Latin names.
Answer: Sodium – Natrium (Na)
Potassium – Kalium (K)
Iron – Ferrum (Fe)
Copper – Cuprum (Cu)
Silver – Argentum (Ag)
13.) What is atomicity of elements?
Answer: Atomicity of elements is defined as the total number of atoms present in a molecule.
14.) Calculate the atomicity of H2SO4.
Answer: Atomicity of H2SO4 is 7.
VI.) Answer in detail
1.) Differentiate metals and non-metals.
Answer:
Metals |
Non-metals |
Metals are very hard and strong. | Solid non-metals are soft and can be easily broken. |
Metals have a shiny lustre. | Non-metals are not shiny and have a dull appearance. |
Metals are sonorous. | Non-metals are not sonorous. |
Metals are malleable and ductile. | Non-metals are neither malleable nor ductile. |
Metals are good conductors of heat and electricity. | Non-metals are poor conductors of heat and electricity. |
2.) Explain the characteristics of compounds
Answer: a) Elements react to form new compound.
b) The composition of each new substance is always fixed.
c) The new substance has totally different properties.
d) The constituents can be separated only by chemical of electrochemical reaction.
3.) Describe the different ways in which we can write the symbols of elements. Give appropriate examples.
Answer: The different ways in which we can write the symbols of elements are
1.) Symbols of elements consist of one or two letters
2.) The symbols of most elements corresponds to the first letter (which is capitalized) of their English name. For example, the symbol for Nitrogen is “N” and that for Carbon is “C”.
3.) We use two letters in symbol of elements when there is more than one element that begins with the same letter.In that two letters the first letter is capitalised while the second letter has a lower case.
For example, the elements hydrogen and helium begin with H. So they represented by the symbol H and He respectively.
Aluminum (Al); Carbon (C); Chlorine (Cl); Mercury (Hg)
4.) Differentiate between elements and compounds.
Answer:
Elements |
Compound |
1.An element represents only one type of atoms e.g. sulphur atoms | A compound represents only one type of molecules e.g. chlorine molecules |
2. An element is made up of one type of atoms. | A compound may be made of same or different atoms e.g. oxygen molecule, carbon dioxide molecule. |
3. An element cannot be broken into anything simpler than it | The constituting elements in a compound can be separated by either physical or chemical method by suitable chemical reactions. |
4. Elements own have certain characteristic properties of their . | Constituting elements in a compound loss their own characteristics. |
5.) Write any five characteristics of compounds.
Answer: Characteristics of a compound
1.) Compounds are homogeneous.
2.) It is obtained by the chemical combination of two or more elements in a definite proportion by mass.
3.) A compound has definite physical and chemical properties.
4.) A compound has a fixed melting and boiling point.
5.) Properties of a compound are entirely different from its constituents.
E.g: water H₂O , Sodium chloride NaCl , etc
6.) Compare the properties of metals and non-metals. Give three examples for each.
Answer: 1.) Metals are very hard and strong whereas Solid non-metals are soft and can be easily broken. Example- Metal – Iron ; Non Metal –
2.) Metals have a shiny lustre whereas Non-metals are not shiny and have a dull appearance. Example – Metal – Gold ; Non Metal- carbon
3.) Metals are sonorous whereas Non-metals are not sonorous. Example- Metal – Tin ; Non Metal- sulphur
7.) Write down the properties of metalloids.
Answer: 1.) Metalloids exhibit the properties of both metals and non metals. Silicon, arsenic, antimony, and boron are some examples of metalloids.
2.) Metalloids have metallic appearance.
3.) They are brittle.
4.) They combine with metals and result in the formation of alloys.
5.) They are positioned in the periodic table on either side of the metals and non-metals.
VII.) Rewrite the given sentence in correct form.
1.) Elements contain two or more kind of atoms and compounds contain only one kind of atom.
Answer: Elements contain only one kind of atoms and compounds contain two or more kind of atom.
VIII.) Higher Order Thinking Skills.
1.) List out the metals, non-metals and metalloids which you use in your house, schools. Compare their properties.
Answer: METAL
1.) Copper is used cooking utensils.
2.) Zinc is mainly used as a protective coat for iron is our house gates.
3.) Sodium is used as a table salt and for flavouring, preserving food.
4.) Coins are made up of nickel.
NON-METAL
1.) Graphite is used in pencil leads.
2.) Carbon is used as a fuel.
METALLOIDS
1.) Silicon is used in glass items. Boron is used in washing powders.
2.) Germanium is used to make transistors.
2.) What changes take place in the movement and arrangement of particles during heating process?
Answer: When an object is heated the motion of the particles increases as the particles become more energetic. If it is cooled the motion of the particles decreases as they lose energy. The change in kinetic energy take place in the movement of particles.
3.) In the diagram given below, the circle, square and triangle represent the atoms of different elements.
Identify all combinations that represent
a.) molecule of a compound
b.) molecule of an element consisting of two atoms
c.) molecule of an element consisting of three atoms
4.) Aakash noticed that the metal latch on gate was difficult to open during hot sunny days. However, it was not difficult to open the same latch at night. Aakash observed that the latch and the gate are exposed to the sun during day time.
a.) Formulate a hypothesis based on the information provided.
b.) Briefly state how you would test the hypothesis.
Answer: a.) Solids get expand when they get on heating and contract on cooling. This phenomena causes change in the volume of matter due to heating it’s volume increases but the mass of matter does not change.
b.) As we have seen during sunny day iron latch get heated due to which the distance between the particles of the iron latch change. In an iron latch the distance between the particles increases and when they gain enough heat . They expand the volume and it come difficult to open the latch on the gate was during hot days . At night, because of cooling the distance between the particles decreases. So at night it was not difficult to open the latch on the gate.
IX.) Consider the following statements and choose the correct option.
1.) Assertion: Oxygen is a compound.
Reason: Oxygen cannot be broken down into anything simpler.
Answer: Assertion is false but reason is true.
2.) Assertion: Hydrogen is an element.
Reason: Hydrogen cannot be broken down into anything simpler.
Answer: b. Both assertion and reason are true, but reason is not the correct
explanation of assertion.
3.) Assertion: Air is a compound.
Reason: Air consists of carbon dioxide.
Answer: d. Assertion is false but reason is true.
4.) Assertion: Air is a mixture of elements only.
Reason: Only nitrogen, oxygen and neon gases exist in air.
Answer: Both statement is false.
5.) Assertion: Mercury is solid in room temperature.
Reason: Mercury is a non-metal.
Answer: Both statement is false.