Science Class X

Carbon has four electrons in its valence shell. Which type of compounds can be formed by carbon atom and why ? Give any one example of such compounds.

An object is kept 40 cm in front of a concave mirror of focal length 20 cm. Find the position and nature of the image. Draw a ray diagram to show the formation of image in this case.

In the reaction:

MnO2 + 4HCl → MnCl2 + 2H2O + Cl2

  1. Name the compound (i) oxidised, (ii) reduced.
  2. Define oxidation and reduction on its basis.

(a) For the preparation of cakes, baking powder is used. If at home your mother uses baking soda instead of baking powder, how will it affect the taste of the cake and why?

(b) How is baking soda be converted into baking powder?

(c) What makes the cake soft and spongy?

In the electrolysis of water,

  1. Name the gas collected at anode and cathode?
  2. Why is the volume of gas collected at one electrode double than the other?
  3. What would happen if dil H2SO4 is not added to water?

"pH has a great importance in our daily life". Explain by giving three examples.

A compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water. Identify the compound and write its chemical formula. Write the chemical equation for its preparation. Mention any one use of the compound.

1 g of solid sodium chloride is taken in a clean and dry test tube and 2 mL of conc. sulphuric acid is added to it. If the gas evolved is tested first with dry and then with wet blue litmus paper, in which case will the litmus paper change colour? Give reason for your answer. What inference can be drawn about the nature of the evolved gas ? Support your answer with chemical equation for the reaction.

Draw the structural formulae of all the possible isomers of the compound with the molecular formula C3H6O and also give their electron dot structures.

What happens when hydrogen is added to a vegetable oil in the presence of nickel? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in this reaction. Write the role of nickel in this reaction.

An object of height 1.2 m is placed before a concave mirror of focal length 20 cm so that a real image is formed at a distance of 60 cm from it. Find the position of an object. What will be the height of the image formed?

Rohit focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and lens as under:
Position of candle = 26.0 cm
Position of convex lens = 50.0 cm
Position of screen = 74.0 cm
i) What is the focal length of the convex lens?
ii) Where will the image be formed if he shifts the candle towards the lens at a position of 38 cm?
iii) Draw a ray diagram to show the formation of the image in case (ii) as said above?

How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?

With the help of one example for each, distinguish between the acquired traits and the inherited traits. Why are the traits / experiences acquired during the entire lifetime of an individual not inherited in the next generation? Explain the reason of this fact with an example.

What are acquired traits? Why are these traits generally not inherited over generations? Explain.

We wish to obtain an equal sized inverted image of a candle flame on a screen kept at distance of 4 m from the candle flame.

  1. Name the type of lens that should be used.
  2. What should be the focal length of the lens and at what distance from the candle flame the lens be placed.
  3. Draw a labelled diagram to show the image formation in this case.

A 5 cm tall object is placed at a distance of 30 cm from a convex mirror of focal length 15 cm. Find the position, size and nature of the image formed.

What is electrical resistivity? Derive its SI unit. In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 100 mA. If the length of the wire is doubled, how will the current in the circuit change? Justify your answer.

Consider the following circuit:

 

What would be the readings of the ammeter and the voltmeter when key is closed? Give reason to justify your answers.

Draw a circuit diagram of an electric circuit containing a cell, a key, an ammeter, a resistor of 4Ω in series with a combination of two resistors (8Ω each) in parallel and a voltmeter across parallel combination. Each of them dissipate maximum energy and can withstand a maximum power of 16W without melting. Find the maximum current that can flow through the three resistors.

Calculate the total cost of running the following electrical devices in the month of September, if the rate of 1 unit of electricity is Rs 6.00.

  1. Electric heater of 1000 W for 5 hours daily.
  2. Electric refrigerator of 400 W for 10 hours daily.

"Improvements in our lifestyle have resulted in greater amounts of waste generation." Give two examples to support the given statement. Suggest one change that we can incorporate in our lifestyle in order to reduce non biodegradable waste.

What do you understand by "Watershed Management"? List any two advantages of watershed management.

What is “Sustainable Management of Natural Resources”? Why is it necessary? Which one out of reuse and recycle, would you practise in your daily life and why?

What is reactivity series? How does the reactivity series of metals help in predicting the relative activities of various metals?

Suggest different chemical processes used for obtaining a metal from its oxides for metals in the middle of the reactivity series and metals towards the top of the reactivity series. Support your answer with one example each.

List in tabular form any three chemical properties on the basis of which metals and non-metals are differentiated.

(a) What was the basis of Mandelẽev’s classification of elements?

(b) List two achievements of Mandelẽev’s periodic tables.

(c) List any two observations which posed a challenge to Mandelẽev’s periodic law.

Write the number of periods and groups in the Modern Periodic Table. How does the metallic character of elements vary on moving (i) from left to right in a period, and (ii) down a group? Give reason to justify your answer.

Na, Mg and Al are the elements of the 3rd period of the Modern Periodic Table having group number 1, 2 and 13 respectively. Which one of these elements has the (a) highest valency, (b) largest atomic radius, and (c) maximum chemical reactivity? Justify your answer stating the reason for each.

An element "X" has mass number 35 and the number of neutrons is 18. Identify the group number and period of "X".

Differentiate between the arrangement of elements in Mendeleev’s periodic table and Modern periodic table.

Explain giving justification the trends in the following properties of elements, on moving from left to right in a period, in the Modern periodic Table.

  1. Variation of valency.
  2. Change of atomic radius.
  3. Metallic to non-metallic character.
  4. Electronegative character.
  5. Nature of oxides.

Name the balloon likes structures present in lungs. List its two functions.

(a) Name the process and explain the type of nutrition found in green plants. List the raw materials required for this process. Give chemical equation for the mentioned process.

(b) Write three events that occur during this process.

Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes.

List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males? How does the use of these techniques have a direct impact on the health and prosperity of a family?

What is vegetative propagation? State two advantages and two disadvantages of this method.

What is variation? How is variation created in a population? How does the creation of variation in a species promote survival?

Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an astronaut on the Moon? Give reason to justify your answer.

Noopur needs a lens of power -4.5D for correction of her vision.

  1. What kind of defect in vision is she suffering from?
  2. What is the focal length and nature of the corrective lens?
  3. Draw ray diagrams showing the (a) defected eye and (b) correction for this defect.
  4. What are the causes of this defect?

Draw a path of light ray passing through a prism. Label angle of incidence and angle of deviation in the ray diagram.

State the cause of dispersion of white light by a glass prism. How did Newton, using two identical glass prisms, show that white light is made of seven colours? Draw a ray diagram to show the path of a narrow beam of white light, through a combination of two identical prisms arranged together in inverted position with respect to each other, when it is allowed to fall obliquely on one of the faces of the first prism of the combination.