Prepare Ammonia gas in Laboratory science 8 to 12

18 . To prepare ammonia gas in the laboratory and study its properties.

AIM : To prepare ammonia gas in the laboratory and study its properties

THEORY : On heating a mixture of ammonium chloride and calcium hydroxide, we get ammonium gas.

APPARATUS : Big hard glass tube, delivery tube, hollow glass tube, Bunsen burner, glass rod, two single-holed rubber cork, four to five gas jar with lids, stand and one CaO bottle as shown in the figure.

CHEMICALS : Calcium hydroxide, ammonium chloride, concentrated hydrochloric acid, red and blue litmus papers.
Prepare Ammonia Gas in Laboratory 
Observation
Colour of ammonia gas :
Odour or smell of ammonia gas :
Ammonia gas is collected by downhard displacement of air therefore it is than air.
Use moist red and blue litmus papers and check the effect on ammonia gas.

Conclude :
Wet red litmus :
Wet blue litmus :

Conclusion : What happens when a glass rod is dipped in concentrated HCL is brought near the mouth of gas jar containing ammonia ?

More details see Video.

Prepare Ammonia Gas in Laboratory Science practical animation video

Endothermic reaction fro std 8 to 10 science

To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.
AIM : To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.
THEORY : During the chemical reaction if the temperature increases the reaction is exothermic and if temperature decreases the reaction is endothermic.
APPARATUS : Conical flask, 250 ml. Beaker, Stand, Thermometer, Glass rod, measuring cylinder, stirrer.
MATERIAL : Dilute hydrochloric acid, Zinc metal, Solid ammonium chloride,

Encothermic reaction
Observation
(1) initial temperature of dilute hydrochloric acid 0 C.
(2) Temperature of the mixture when Zinc metal dissolves in hydrochloric acid = 0 C.
(3) Difference of temperature = 0 C.
(4) Give chemical reaction of Zinc metal with hydrochloric acid.

NOTE :

 (1) Similarly heat of neutralization in neutralization reaction between dilute hydrochloric acid and sodium hydroxide can be measured.
(2) The increase in temperature can be noted when dissolution of solid sodium hydroxide in water is carried out.

PRACTICAL USES
The combustion reactions of kerosene, Petrol, LPG are exothermic, therefore these substance are used as fuel.

NOTE : * Similarly when Sodium nitrite is dissolved in water decrease in temperature occurs.

More Video about Endothermic reaction

Endothermic reaction animation video.

Exothermic reaction for std 8 to 10

To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.

AIM : To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.

THEORY : During the chemical reaction if the temperature increases the reaction is exothermic and if temperature decreases the reaction is endothermic.

APPARATUS : Conical flask, 250 ml. Beaker, Stand, Thermometer, Glass rod, measuring cylinder, stirrer.

MATERIAL : Dilute hydrochloric acid, Zinc metal, Solid ammonium chloride,
Exothermic reaction
Observation : 
(1) initial temperature of dilute hydrochloric acid 0 C.
(2) Temperature of the mixture when Zinc metal dissolves in hydrochloric acid = 0 C.
(3) Difference of temperature = 0 C.
(4) Give chemical reaction of Zinc metal with hydrochloric acid.

NOTE :
 (1) Similarly heat of neutralization in neutralization reaction between dilute hydrochloric acid and sodium hydroxide can be measured.
(2) The increase in temperature can be noted when dissolution of solid sodium hydroxide in water is carried out.

PRACTICAL USES
The combustion reactions of kerosene, 
Petrol, 
LPG are exothermic, 
therefore these substance are used as fuel.

more Video presentation:


Exothermic reaction animation video

Focal Length by an Image of far distance object for std 8 to 10

To determine the focal length of a convex lens by obtaining an image of a far distance object. 

AIM : To determine the focal length of a convex lens by obtaining an  image of a far distance object.
PRINCIPLE :  Rays parallel to the axis, after being refracted by a convex lens, are focused on the principal focus. Distance   between the optical centre and the principal focus is known as the focal length.
APPARATUS   :   Convex lens, Stand, Screen, Foot-rule, etc,.
Focal length of a  far distance object
Observation : Distance between the optical center of the lens and the image on the screen = Focal length of the lens  f =   cm...         
Practical uses : Convex lens of proper focal length are used in optical instruments like simple microscope, compound microscope, telescope, etc,. Also the method given here in the simplest way to estimate the focal length of a convex lens.




To determine the focal length of a concave mirror by far away image.

2. To determine the focal length of a concave mirror by obtaining an image of a far distance object

AIM :- To determine the focal length of a concave mirror by obtaining an image of a far distance object.
APPARATUS  :- A concave  mirror of diameter approximately 10 cm., stand, screen, foot-rule, etc.
PRINCIPLE   :- Rays coming from a far distance object are almost parallel. Such rays, parallel to the principal axis, after being reflected by a concave mirror, are focused at the principal focus of the mirror. Distance between the principal focus and the pole of the mirror is known as the focal length.
NOTE  :  Here screen should be taken small, so that rays coming from the object are    not blocked by the screen itself. Diameter of the screen here can be   approximately 3 – 4 cm.
Focal Length of Concave mirror
Parallal rays of a Image 
Focal length of image on concave mirror
OBSERVATION
Distance between the pole of the mirror and the image on the screen = focal-length =                            CM.
CONCLUSION
PRACTICAL USES
Concave mirrors are used in head lights of vehicles, solar furnace, solar cooker, shaving mrror, etc. For all such applcatons it is necessary to know the focal length of the mirror to used. It can be estimated using the given method.


Video
To determine the focal length of a concave mirror by obtaining an image of a far distance object.
Focal length of concave mirror of a far away image.wmv

Angle of Incidence, Angle of image through Glass Slab experiments for std 8 to 12


To draw the path of a ray passing through a glass slab and, hence, to measure the angle of incidence and the angle of image.
AIM : To draw the path of a ray passing through a glass slab and, hence, to measure the angle of incidence and the angle of image.
PRINCIPLE :     When an oblique ray of light enters from one      transparent medium to another transparent medium,  at the surface separating these two media, the light  ray changes its path. This phenomenon is called  refraction of light. When a ray of light passes through  a glass-slab, it is refracted twice, as a result of which, the emergent ray becomes parallel to the incident ray.
APPARATUS :   Glass –slab, Drawing-board, Drawing paper (White),  Foot-rule, Pencil, Pins, Push pins and Protractor.
Paper fit with pins and set Glass Slab


Ø  Fix a white drawing-paper on the drawing board using push pins.  Now place the glass-slab on it and mark its position PQRS by drawing its out-line using a pencil.
Draw Ray AB not perpendicular to PQ

Ø  Now draw a ray AB such that it is not perpendicular to PQ. Fix two pins upright with separation of 2-3 cm on this ray.
See Image from another side and set P3 P4
Ø    Now try to see the images of P1 and P2 from side RS and fix pins P3  and P4 upright so that images of P1 and P2 and pins P3 and P4 become collinear at their lower ends.
Remove pins and Glass slab
Ø  Now remove the slab and the pins obtain emergent ray CD by drawing a line passing through marks of P3 and P4, which intersects RS at C.
Ø  Join  B and C to complete the path of the ray. Now draw a normal MN to the surface PQ in such a way that it passes through B. Also       draw M’N’, through C to the surface RS.
Measure Angle of Incidence and Angle of Emergence.
Ø  Measure ÐAMB (Angle of Incidence) and ÐOCN’ (Angle of Emergence).
By changing Angle of Incidence repeat the experiment
Ø  Repeat the experiment for various values of angle of incidence AMB and note your observations in the table.


Verify laws of Reflection using Plain Mirror Experiments with video presentation for std 10


1.  TO VERIFY THE LAWS OF REFLECTION USING A PLANE MIRROR
Aim : To verify the laws of reflection using a plane mirror.
Principle : When a ray of light is incident on a reflecting surface, it changes its direction of motion and travels in the original medium following certain laws. This phenomenon is called reflection of light.
Apparatus : Drawing board, a drawing paper (White), a plane mirror, a foot-rule, a pencil, four pins, four push pins, a protactor, a stand for the plane mirror.


Ø First of all fix the white drawing paper on the drawing board using push pins.
Pins up Paper on Wooden board
Ø First of all fix the white drawing paper on the drawing board using push pins. Place the plane mirror along with its stand and fix its position AB.
Verify Laws of Reflection using plain Mirror

Ø Now draw a line PQ which passes through the mid-point ‘P’ of AB and perpendicular to AB.
Ø PQ is called the normal to AB.
Law of Reflection Of Plain Mirror

Ø Draw a ray RP which makes some angle with the normal (PQ).
Ø Draw a ray RP which makes some angle with the normal (PQ). On the ray RP fix two pins P1 and P2 vertically with 2-3 cm separation between them. Ray RP is incident ray.
Reflection using Plain Mirror
Ø Now from the other side of PQ , (in which incident ray is not there) see the images of pins P1 and P2 fix other two pins P3 and P4 vertically so that pins P3, P4 and images P1 and P2 appears collinear at their lower ends.
To Verify Laws of Reflection using Plain Mirror

Ø Now remove the pins and the mirror. Join the marks of P3 andP4 and obtain the reflected ray PS.
Reflection by a Plain Mirror
Ø Repeat  the experiment for different angles of incidence. Measure angle of incidence and angle of reflection. Note your reading in the observations table.
Observation of Reflection of Plain Mirror
Conclusion :
Practical Uses:
We can study the laws of reflection. We can also study the images obtained by the plane mirror. We can come to know how reflection is used in various optical appliances, e.g., periscope, keleidoscope.

Video :
To Verify the Laws of Reflection using Plain Mirror