Class 10
Revision questions

1.      A substance “X” Which is an oxide of a group 2 element is used for white washing. On treatment with        water it forms “Y” .The solution of “Y” turns red litmus blue.

(a)    Identify  “X” and “Y”

(b)   Write the chemical equation

(c)    Explain reason why red litmus changes to blue.                                                                                                                                                                                                         (1+1+1)                                                                                                

2.      Based on the reactions given below, arrange the metals involved in these reactions in decreasing                

              order of reactivity. Give suitable explanation.

(i)Zn+CuSO₄ → ZnSO₄+ Cu, 

(ii) Cu+2AgNO_3→Cu(NO₃)₂   ,

(iii)Zn+FeSO₄→ ZnSO₄ + Fe

               (iv)  Fe+ CuSO₄→FeSO₄+Cu.

      (b).What is the nature of the reactions?                                                                                                                                                                                                                             (2+1)

3.      (a) How does baking soda help in extinguishing fire?                                                                                                                                                                                             (1+1+1)   

(b) What is a difference between the two: CaSO₄.2H₂O and 2 CaSO_4. H₂O

            (c) When a drop of grape juice solution is placed on a strip of pH paper .

                 What will be The possible colour of the paper: Deep red or Orange .? Why?        

4.                  4  (a) Electrolysis of strong solution of NaCl is also called Chlor-alkali process   Why?                                                                                                                                                                   (1+1+1)

             (b) What effect does the concentration of H⁺(aq) ions have on the nature of the solution?

             (c) What would you observe on adding dilute HCl to baking soda

.           5. a) The reaction of metal X with ferric oxide solution is highly exothermic in nature and                        used to join  ailway tracks. Identify the X and write the equation with ferric oxide.

               (b) Show the formation CaO by the transfer of electron.

             (c) You are provided with two metals: Sodium and Magnesium .Using only water as the                         reactant,  how will you identify them?

  (d) To convert Zinc sulphide to Zinc oxide is calcination is a best option or not?. Give reason

              (e)Explain why are ionic compounds usually hard?     

            6 An athlete won a bronze medal in a race competition. After some days, he found that the                     medal    had lost its lustre due to the formation of greenish layer on it. Name the metal                         present in the medal. What is the reason for appearance of greenish layer on its                                       surface? 

                7 A reaction is carried out in which a clear aqueous solution of lead (II) nitrate is mixed                       with a solution   of potassium iodide.  A thick yellow precipitate forms in the test                                tube.                                                   (1+1)

a)      Write the name and formula of the two products in this reaction.

b)      What type of reaction is this?

          8. A student dipped strip of pH paper in distilled water taken in atube. As expected the colour               of pH paper remain same. He then dissolved a pinch of common salt in the same test tube.                       What will   be the expected change in colour?

           9 Shweta take two test tubes marked as A and B provided with rubber cork. In the test tube                     marked A   she pour some boiled distilled water along with some oil and in second test tube                   she pour some water.She puts iron nail to both the test tube . What she observe with the                     passage of time?                                                                                                                                                                    

 class 7 CBSE WORKSHEET -TIME AND MOTION

Q1. Define speed. State its S. I. unit.

Q2. Differentiate between uniform and non-uniform motion.

Q3. Describe a simple pendulum. Draw a diagram. What kind of motion does it show? How can the time period of pendulum can be increased or decreased?

Q4. For a simple pendulum; define:-

        a) One oscillation

        b) Time period

        c) Frequency

Q5. A truck travels a distance of 540 km in 4.5 hours. Calculate its speed.

Q6. The distance between two stations is 1995 km. How much time it will take to cover this distance at an average speed of 19 km/h?

Q7. A car takes 20 minutes to cover a distance of 15 km. Calculate its speed in km/h.

Q8.Convert 45m/s into Km/h.

Science CLASS VII

ELECTRIC CURRENT AND ITS EFFECTS

Q1.Fill in the blanks :

1. A combination of two or more cells is called a _____________ .

2. The working of a an electric bulb, electric iron and the fuse is based on the __________________ effect of current.

3. The filament of an electric bulb is made up of ____________ 

4. Instead of electric bulbs, it is advisable to use __________________ , in order to reduce wastage.

5. __________ is a safety device which prevents fires and damage to electrical Appliances.

6. A current carrying coil wrapped around a piece of iron is called an __________.

7. Electric fuse has ________ melting point.

8. _________________ and _____________ are devices which have electromagnets in them.

9. Amount of heat produced in a wire depends on the length,materal and _________ of the wire.

10. In a fan energy gets converted into ___________ energy

11.Two devices where heating effect of electric current is used are ___________ and _____________

12.Heating effect is more in  long wire and ______________ in a short wire. wire .

13. When a magnetic compass is brought near a circuit carrying current it shows ________________

14.___________ is a device which is wound around  a hollow metallic core and used as an elecromagnet.

15. Draw diagram of a closed electric circuit using symbols which consists of

-two cells (battery),-a switch,-bulb and wire.Also show the direction of electric current

What will happen if we bring a magnetic compass near it.

 Answers-Battery ,heating effect ,tungsten, CFL,  fuse ,electromagnet, low, electric bell and loud speakers ,thickness, mechanical, electric toaster and electric iron, less, deflection, solenoid

mechanical, electric toaster and electric iron, less, deflection,solenoid