Grade -6(CHEMISTRY)
Worksheet
NAME: ___________________
Lesson-7
Roll No: ______
Water
Q.1 What is surface water?
Ans: Any source of water that flows or is stored on the surface of the earth known as surface of water.
Q.2 What is underground water?
Ans: Rain water or the water from water bodies seeps into the ground to collect above the non - porus rocks as
underground water.
Q.3 Write two surface of
Surface water- River , lakes , Streams
Underground water - Well , Springs
Q.4 Why is rain water considered as purest form of drinking water?
Ans: Rain water is purest form of drinking water because it is usually free from impurities.
Q.5 Why is bleaching powder added to water in waterworks?
Ans: When bleaching powder is dissolved in water it releases chlorine which kills germs.
Q.6 Name any two methods at home to make water fit for drinking.
Ans: Boiling , Filteration.
Q.7 List major three causes of water pollution.
Ans: Oil Spillage : Drilling of oil wells and shipping operations cause oil spills which result in water pollution.
Dumping of garbage into water bodies cause water pollution.
Q.8 What is conservation of water?
Ans: Preventing the wastage of water without disturbing day to day life.
Q.9 State the three states of water .How is the inter changeability of three states of water achieved?
Ans: Water is available in solid, liquid , gaseous state in nature.
Interchangeability : On heating ice melts and change to water.
On cooling , water changes into ice.
On heating, water changes into water vapour.On cooling water vapour changes into water.
Q.10 Explain the water cycle with the help of diagram also write the importance of the cycle.
Evaporation :- The sun heats up water in rivers, lakes , seas and oceans into water vapour .Plants aso add some
amount of water vapour through transpiration
Condensation: - Water vapour beings lighter rises up .The cool air higher up in the atmosphere cools the water
vapour and it condenses to form water droplets. These water droplets join together and form clouds.
Precipitation : - When tiny droplets join together to form larger droplets become heavy and fall down on the
earth.
Importance of water cycle:
The water cycle helps in controlling the climatic conditions.
It helps in restoring the water lost from the earth's surface and maintain the balance of water on the earth .
Cultivation of crops mostly depends on rain water.
Q.11 Explain the methods used for removal of (a) suspended impurities. (b) Germs from water
Purification of drinking water
Removal of suspended
impurities
Destruction of germs
Sedimentation
Loading
Chlorination
Filteration
Q.12 State the uses of water.
Ans : Water is good solvent .The nutrients and minerals present in our food get dissolved in water.So
that our body is able to absorb them easily.
Water regulates the body temperature.
It is used in our household works such as cleaning , cooking , bathing etc
Water is also used in industries. It is used in agriculture.
Q.13 List five ways to reduce water pollution.
The chemical waste released from industries should be treated in effluent treatment plants to remove
harmful chemicals present in them.
Sewage should be treated in sewage treatment plants before being released into rivers.
Excessive use of insecticides and pesticides should be reduced. Organic farming should be
encouraged.
Wherever possible waste products from factories should be recycled and used before being released.
The use of detergents should be reduced.
Lesson-8 Rocks and minerals.
Q.14 Name the three type of rocks.
Ans: Sedimentory rocks , Metamorphic rocks , Igneous rocks
Q.15 What are igneous rocks? Give two example .
Ans: Due to volcanic eruption underground molten rocks rises above the earth's surface and cooled
down and form igneous rocks.eg. Granite , Basalt , Pumice , Tuff , Obsidian
Q.16 Why are sedimentary rocks are called secondary rocks?
Ans: Sedimentary rocks are formed by sediments , particles, grains or fragments derived from
previously existing primary rocks . The action of wind and water breaks up the primary rocks into
smaller particles such as clay or sand are carried by running water and settle at the bottom of river ,
seas and lakes layers by layers as sediments. Over a period of time , the sediments thickens as mre
materials is added to them. And under pressure transform into hard rock called sedimentary rocks.
These form from other rocks so called secondary rocks.
Q.17 What are metamorphic rocks? Give two examples.
Ans : Metamorphic rocks are formed when igneous rocks and sedimentary rocks are subjected to
high temperature and pressure.eg. Slate, , Quartzite , marble , gneiss.
Q.18 Why are fossil fuels are called non renewable resources?
Ans: Fossil fuels take millions of years to form inside the earth's crust. Their reserve under the earth's
crust is limited with rapid industrialization and urbanization , the use of fossil fuels are called non
renewable resources.
Q.19 Explain rock cycle.
Magma
Melting
Cooling
Metamorphic rocks
Heat & Pressure
Igneous rocks
Heat & Pressure
Weathering
Sedimentary rocks
Sediments
Q.20 How many types of minerals are there? Explain with examples?
Ans: There are three types of minerals . Metallic minerals , Non- metallic minerals, Organic minerals.
Metallic minerals:
Minerals which contain metallic substances are called metallic minerals. Most of minerals of iron ,copper,
aluminium, lead, zinc and gold are obtained from igneous or metamorphic rocks.
Non-metallic minerals
Minerals which contain non-metals substances are called non- metallic minerals mica, talc, sand, gypsum.
Organic minerals
Minerals like petroleum and coal are organic minerals. These are found in sedimentary rocks.
Q.21 How is coal formed? Name the different varieties of coal?
Ans: Coal is formed by the decay and decomposition of large plants that were buried under the earth millions
of year ago. Due to high temperature and high pressure inside the earth and in the absence of air , the plants
got converted into coal. Lignite, bituminous, anthracite, peat are the types of coal.
Q.22 Name the main products obtained from crude oil by fractional distillation?
Ans: Petroleum gas, Petrol, Kerosene, fuel oil, lubricating oil, paraffin wax, asphalt etc are product by
fractional distillation of petroleum.
Q.23 Many pumice rocks float in water.
Ans: Pumice has many tiny pores which are formed by gases trapped inside them at the time of formation.
These rocks are so light in weight .so pumice float in water.
Q.24 Sedimentary rocks are formed in layers.
Ans: Sedimentary rocks are formed in layers because these rocks are made up of sediments which layers on
river, seas, lakes beds.
Lesson-6 Air
Q.25 What is atmosphere?
Ans: The blanket of air that envelops the earth is called atmosphere.
Q.26 Name the components of air.
Ans: Nitrogen, oxygen, carbon dioxide, inert gases, water vapour, dust particles , impurities.
Q.27 Is a mixture or a compound?
Ans: Air is a mixture because in air number of gases are present in any proportion (amounts).
Q.28 What is a result when CO2 is passed through lime water?
Ans: Lime water becomes milky.
Q.29 Difference between combustion and respiration.
COMBUSTION
RESPIRATION
1.Oxygen is required.
1. Oxygen is required.
2. It is slow processs.
2. It is quick process.
3. It takes place at room temperature.
3. It takes place at any temperature.
Q.30 Name the products obtained when fuels are burnt.
Ans: CO2 + Water vapour + energy.
Q.31 What are the two main processes that maintain the oxygen- carbondioxide balance in nature?
Ans: Respiration & Photosynthesis
Q.32 Explain galvanization.
Ans: Iron objects are coated with the thin layers of zinc metal is called galvanization.
Q.33 What is rusting of iron? State the condition required for rusting ?
Ans: When an iron object is left in damp air for a long time. It gets covered with a reddish brown flaky
substance is called rust.
Condition necessary for rusting of iron.
Presence of air.
Presence of water.
Lesson-5 Changes around us
Q.34 Examples of physical change.
Ans: 1) Dissolving sugar in water.2) Glowing of an electric bulb. 3) Drying of wet clothes 4) Melting of wax 5)
Mix salt in water.
Q.35 Examples of chemical change.
Ans: Burning of wood, Formation of curd from milk, rusting of iron, photosynthesis, burning of iron crackers.
Q.36 Differences.
Natural
Man-made
1.It occurs naturally.
2. eg. Rain fall, season change etc
1.It is made by man
2. to build house, make chalk etc
Slow change
1.Changes that occur over long period of time are
called slow change.
2.eg. freezing of water, formation of soil.
Fast change
1. changes that occurs with in a very short period of
time is known as fast change.
2. Inflated balloon, bursting of crackers
Periodic change
1. Changes that are repeated at regular intervals are
called periodic change.
2. eg. Change of seasons, change ofday & night
Non periodic change
1. Changes that may occur at any time are called non
periodic change.
2.eg. a dust storm, landslides etc
Reversible change
1. A change that can be reversed.
2. e.g. Dissolving sugar in water, glowing of bulb
Irreversible change
1. A change that can not be reversed.
2. e.g. rusting of iron , curd from milk.
Q.37 Explain why the burning of a candle is an example of both physical as well as chemical change?
Ans: During the burning of candle some wax melts and solidifies back to wax on cooling. This shows that
melting of wax is physical change.
During burning of candle some wax undergoes combustion. It produces new substances.CO2 and water vapour
.so this also shows chemical change.
Q.38 Explain energy change in a chemical change.
Ans: In a chemical change the molecules and atoms rearrange them selves to form new substances. This
rearrangement involves some energy changes. Energy is released in some chemical changes while in others it is
absorbed. Energy in the form of heat and light is released in chemical changes which involves burning of
substances. Energy in the form of sunlight is absorbed in the process of photosynthesis.
Q.39 To show that heat is evolved when water is added to quicklime.
Requirements : A beaker, quicklime, water
Figure:
Energy evolved
Beaker
----------------------------------------------------------------------------------
Water+ quicklime
Procedure: Take a small quantity of quicklime .
Slowly add water to this .
Touch the beaker, How does it feel?
Observation: 1111the beaker is found to become very hot.
Conclusion: Heat is evolved when water is added to quicklime.