Sunday, May 28, 2017
Tuesday, May 23, 2017
Monday, May 22, 2017
Changes around us
GENERAL SCIENCE
STD: 6 Le – 6, CHANGES
AROUND US
Learning Objectives:
·
To differentiate reversible and irreversible changes
·
To analyze the factors that brings about changes in different substances
·
To classify the changes into physical and chemical changes
Answer The Following:
1. Differentiate between reversible
and irreversible changes with examples.
The changes that be reversed easily to obtain a substance in
its original form is called a reversible change.
Eg:- When we heat ice, it melts to form water. If we cool
this water, it again changes into ice. So, the changing of ice into water has
been reversed by cooling. Thus melting of ice is a reversible change.
The change that cannot be reversed to obtain a substance back
in its original form is called an irreversible change.
Eg: Burning of paper, cooking of food.
2. What happens to a material’s size
when it is (a) heated (b) cooled?
Many materials increase in size or expand on heating and
decrease in size or contract on cooling.
For example, metals like iron and aluminium expand on heating
and contract on cooling.
3. How heating and cooling of water
brings changes in the state of matter?
When we boil water, it changes into steam. If we cool steam,
it again changes into water. So, the changing of water into steam has been
reversed by cooling. Thus, the boiling of water is a reversible change.
4. Explain how a metal rim is fixed
around the wooden wheel of cart.
In bullock carts wooden wheels are fitted with iron rims to
make them last longer. The iron rim is made slightly smaller in size than the
wooden wheel. The ironsmith heats this iron rim uniformly over a dry dung-cake
fire. On heating the iron rim expands and becomes somewhat bigger in size. This
is now easily put around the wooden wheel. Water is then poured over the hot
iron rim to cool it. On cooling the hot iron rim contracts and fits tightly
around the wooden wheel.
5. What are the kinds of changes
caused by pressure?
Pressure can cause many kinds of changes. Some important ones
are:
(1) Change in shape and size: If we press fluffy solids like a cushion or a ball of wool
their shape changes. When the pressure is released, they get back to their
original shape. A gas balloon changes its shape and size when filled with gas.
When the balloon deflates, the shape and size again changes.
(2) Breaking objects: When pressure is applied on brittle substances like
glass or biscuits, they break into pieces. It is an irreversible change.
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Saturday, May 13, 2017
Sources of Food, Components of Food, Fibre to Fabric
LESSON – 2
COMPONENTS OF FOOD
Learning Objectives:
v Able to classify foods according to food components.
v To analyze the tests for starch, proteins and fats.
v Able to create a balanced diet.
v To identify different deficiency diseases and the
cause of those diseases.
Answer the
following:
1.
Define the following terms:
(a) Nutrients
Ans: Nutrients
are the substances that an organism needs for growth, repair and maintenance of
its body. The nutrients needed by the human body are carbohydrates, fats,
proteins, vitamins and minerals.
(b) Balanced diet
Ans: The diet that contains adequate
amount of all essential nutrients, roughage and water for the proper growth and
development of the body is called a balanced diet.
(c)
Deficiency Diseases
Ans: Diseases that are caused due to the lack of
carbohydrates, fats, proteins, minerals or vitamins in our diet are called
deficiency diseases.
2.
How will you test the
presence of starch in a given food sample?
Ans: Take a small piece of the food
material and add a few drops of diluted iodine solution using a dropper. If the
food sample contains starch, it will turn blue-black.
3.
What is roughage? Why
is it important to include roughage in our diet?
Ans:
The fibrous undigestable material present in our food is called as
roughage. Roughage helps our body to get rid of undigested food and thereby
prevents constipation. Also it can absorb a great amount of water and helps to
retain water in the body.
4.
Give two cooking
practices that lead to the loss of nutrients in food materials.
Ans:
(1) If
cooking is done in excess of water and the water is thrown away after cooking,
many water-soluble vitamins and minerals are lost.
(2) If cooking is done at a high temperature, many
proteins and vitamins are destroyed.
5.
Name three deficiency
diseases and also write their causes and symptoms.
|
Deficiency diseases
|
Causes
|
Symptoms
|
|
1.
Night blindness
|
Due to lack of vitamin A
|
Poor vision and loss of vision in darkness.
|
|
2.
Beriberi
|
Due to lack of vitamin B
|
Feels extremely weak, Swelling of legs, Loss of
appetite and weight.
|
|
3.
Scurvy
|
Due to lack of vitamin C
|
Spongy and bleeding gums.
|
6.
What is obesity? What are its causes?
Ans: The overeating of fat
rich foods will lead to an overweight condition called obesity. An obese person
suffers from heart-related problems. Many people especially children, eat a lot
of junk food such as burgers, chips and soft drinks. All these food items
contain large amounts of fats and sugars. Due to lack of physical activity,
fats get accumulated in the body and cause obesity.
Activities:
1. Collect pictures of children suffering from the
following deficiency diseases and write its causes, symptoms and prevention of
those diseases.
(a)
Kwashiorkor (b) Marasmus (c) Nightblindness (d) Scurvy (d) Rickets
2.
Make a list of any
three junk foods, write their ingredients and the harmful effects of their
excessive intake.
New Terms:
1.
Nutrients
2.
Carbohydrates
3.
Roughage
4.
Deficiency diseases
5.
Kwashiorkor
6.
Marasmus
7.
Obesity
8.
Goitre
9.
Anaemia
10. Balanced diet
Lesson- 3 FIBRE TO FABRIC
Learning Objectives:
Ø To identify
different types of fibres and their uses.
Ø
To analyze the ways by which fabrics are made from
fibres.
Answer the following:
1.
What is meant by yarn?
The loose thread in a
fabric is called yarn.
2.
Differentiate between
natural fibres and synthetic fibres.
The fibres obtained from
plants and animals are called natural fibres. Eg: Cotton, silk
Fibres that are made by
man from different chemicals in the industries are called man-made or synthetic
fibres. Eg: Nylon, Polyester
3.
Write any two uses of
jute fabrics.
1 .
Jute yarn is used for making gunny bags or sacks and
for wrapping packages.
2 .
High quality jute fibres are woven into curtains,
carpets, chair coverings and packing for linoleum.
4.
List the steps involved
in the preparation of fabrics.
The following steps are
involved in the preparation of fabrics:
(i)
Obtaining fibre.
(ii)
Preparation of yarn from fibres by spinning.
(iii)
When two sets of yarn are involved, yarns are woven on
looms to make a fabric. When a single yarn is used, the fabric is prepared by
knitting.
5.
What is meant by
ginning?
The process of separating
seeds from the cotton fibres is called ginning of cotton. It is done by hand or
machine.
6.
How is weaving
different from knitting?
The process of arranging
two sets of yarns together to make a fabric is called weaving.
Knitting is a process of
making fabric in which only a single yarn is used.
7.
Explain the method of
making yarn from fibre.
The process of making
yarn from fibre is called spinning. In this process, fibre from a mass of
cotton are drawn and twisted. This brings the fibres together to form a yarn.
The simple devices used for spinning are hand spindle and charkha. On a large
scale, spinning is done with the help of spinning machines.
-----------------------------
Activity:
1.
With the help of pictures explain the process of
making cotton fabric from cotton fibre.
2.
Do weaving process using colour papers and place it in
your activity file.
New terms:
|
1.
Fabric
2.
Synthetic fibres
3.
Knitting
4.
Spinning
5.
Weaving
|
6.
Ginning
7.
Powerlooms
8.
Roller gin
9.
Polyester
10.
Terrysilk
|
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