Q: You are given a cylindrical vessel with a frictionless movable
piston. Water is taken in the vessel and it is heated by putting
weights on the piston.
a) How can you know when the boiling process of water started?
b) If the weights on the piston are increased what happens to the
boiling point of water?
A: a) The weights fall down when the boiling process starts.
b) There is no change in the boiling point of water, when the weights on the
piston are increased. This is because, as the piston is a frictionless
movable one, any increase in pressure in water pushes the piston
upwards.
Q: How much energy is released or absorbed when 1 gm. of water at 0°C
freezes to ice at 0°C?
A: Given: m = 1 gm.
Latent heat of fusion of ice L = 80 Cal/gm (We know)
Formula: Energy released Q = mL Cal.
Substituting the values: Q = 1 × 80 = 80 Cal.
Q: Why is slaked lime used for white washing walls?
A: A solution of slaked lime produced is used for white washing of walls.
Slaked lime (Calcium hydroxide Ca (OH)2) reacts slowly with the Carbon
dioxide in air to form a thin layer of Calcium Carbonate on the walls.
After two to three days of white washing, Calcium Carbonate formed
gives a shiny finish to the walls.
Q: Are the process of evaporation and boiling the same? (1 Mark)
A: Boiling of a liquid differs essentially from evaporation.
Evaporation takes place at any temperature while boiling occurs at a
definite temperature called the boiling point.
Q: Mention the uses of Propane, giving its formula. (1 Mark)
A: Propane is a colourless and odourless gas often used as a heating
and cooking fuel. ★ Its chemical formula is C3H8.
Tenth Class Physical Sciences Important Questions - New Syllabus
Q: You know that Archimedes burned ships using mirrors.
a) What type of mirrors were used?
b) Which energy was put to use for burning?
c) Mention the principle in this process.
d) Draw a ray diagram showing this principle. (4 marks)
A: a) Archimedes used concave mirrors for burning the ships.
b) Solar energy was put to use for burning.
c) Archimedes focused the image of the Sun on the ships by adjusting
the concave mirrors in such a way that their focus lie on the ships.
d) Ray diagram is shown below.
Q: What are your observations about the effects of Oxidation reactions
in daily life. Can you suggest any preventive measures for them? (4
marks)
A: When some metals are exposed to moisture, acids ... etc., they
tarnish due to oxidation. This is called Corrosion.
Tarnishing of silver ware, green coating on copper are some examples for this.
Corrosion causes damage to car bodies, bridges, iron railings, ships
and to all other objects that are made of metals. Corrosion can be
prevented or at least minimised by shielding the metal surface from
oxygen and moisture. It can be prevented by painting, oiling,
greasing, galvanizing, chrome plating or making alloys.
When fats and oils are oxidized they become rancid. Their smell and
taste change. Rancidity is an oxidation reaction. The spoilage of
these food items can be prevented by adding preservatives like Vitamin
C and Vitamin E. Keeping food in air tight containers helps to slow
down oxidation process.
a) What type of mirrors were used?
b) Which energy was put to use for burning?
c) Mention the principle in this process.
d) Draw a ray diagram showing this principle. (4 marks)
A: a) Archimedes used concave mirrors for burning the ships.
b) Solar energy was put to use for burning.
c) Archimedes focused the image of the Sun on the ships by adjusting
the concave mirrors in such a way that their focus lie on the ships.
d) Ray diagram is shown below.
Q: What are your observations about the effects of Oxidation reactions
in daily life. Can you suggest any preventive measures for them? (4
marks)
A: When some metals are exposed to moisture, acids ... etc., they
tarnish due to oxidation. This is called Corrosion.
Tarnishing of silver ware, green coating on copper are some examples for this.
Corrosion causes damage to car bodies, bridges, iron railings, ships
and to all other objects that are made of metals. Corrosion can be
prevented or at least minimised by shielding the metal surface from
oxygen and moisture. It can be prevented by painting, oiling,
greasing, galvanizing, chrome plating or making alloys.
When fats and oils are oxidized they become rancid. Their smell and
taste change. Rancidity is an oxidation reaction. The spoilage of
these food items can be prevented by adding preservatives like Vitamin
C and Vitamin E. Keeping food in air tight containers helps to slow
down oxidation process.
10th Biology New Syllabus - Experiment Questions on Photosynthesis
When an experiment is given as a question, draw the diagram first and
then label it. Then, write the format of the experiment. Explain your
observations and the inference you obtained at the end. When an
experiment is given as a question, other logical questions will also
be given. You should draw the diagram, write the experiment, and then
answer the additional questions too.For example..
Q. How do you prove that carbon dioxide is necessary for photosynthesis.
a. Why is this experiment called Mohl's half leaf experiment?
b. How do you de-starch a plant?
A: De starching a plant: to de-starch a plant, we need to keep the
plant in dark for about a week.
Aim: To prove that Carbon dioxide is necessary for Photosynthesis
Apparatus required wide mouthed transparent bottle, destarched plant,
potassium hydroxide pellets / potassium hydroxide solution, split
cork.
Procedure: Arrange the apparatus as shown in the figure. Take the wide
mouthed transparent bottle. Put potassium hydroxide pellets /
potassium hydroxide solution
in the bottle. (Potassium hydroxide absorbs carbon dioxide) ★ Insert
split cork in the mouth of the bottle.
Insert one of the leaves of de starched plant (through a split cork)
into transparent bottle containing potassium hydroxide dioxide
pellets/potassium hydroxide
solution. Leave the plant in sunlight. After a few hours, test this
leaf and any other leaf of this plant for starch.
Observation: The leaf that was exposed to the atmospheric air becomes
bluish black, and the one inside the flask containing potassium
hydroxide that absorbs carbon dioxide in the bottle does not become
blue-black.
Inference: This shows that carbon dioxide is necessary for photosynthesis.
a. Name of the experiment is taken from its inventor name. It is
called as Moll's half leaf experiment because Moll has divided the
leaf into two half portions one inside the bottle and other outside.
b. To de-starch a plant, we should keep the plant in dark for about a week.
then label it. Then, write the format of the experiment. Explain your
observations and the inference you obtained at the end. When an
experiment is given as a question, other logical questions will also
be given. You should draw the diagram, write the experiment, and then
answer the additional questions too.For example..
Q. How do you prove that carbon dioxide is necessary for photosynthesis.
a. Why is this experiment called Mohl's half leaf experiment?
b. How do you de-starch a plant?
A: De starching a plant: to de-starch a plant, we need to keep the
plant in dark for about a week.
Aim: To prove that Carbon dioxide is necessary for Photosynthesis
Apparatus required wide mouthed transparent bottle, destarched plant,
potassium hydroxide pellets / potassium hydroxide solution, split
cork.
Procedure: Arrange the apparatus as shown in the figure. Take the wide
mouthed transparent bottle. Put potassium hydroxide pellets /
potassium hydroxide solution
in the bottle. (Potassium hydroxide absorbs carbon dioxide) ★ Insert
split cork in the mouth of the bottle.
Insert one of the leaves of de starched plant (through a split cork)
into transparent bottle containing potassium hydroxide dioxide
pellets/potassium hydroxide
solution. Leave the plant in sunlight. After a few hours, test this
leaf and any other leaf of this plant for starch.
Observation: The leaf that was exposed to the atmospheric air becomes
bluish black, and the one inside the flask containing potassium
hydroxide that absorbs carbon dioxide in the bottle does not become
blue-black.
Inference: This shows that carbon dioxide is necessary for photosynthesis.
a. Name of the experiment is taken from its inventor name. It is
called as Moll's half leaf experiment because Moll has divided the
leaf into two half portions one inside the bottle and other outside.
b. To de-starch a plant, we should keep the plant in dark for about a week.
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