Choose the correct answer. velocity changes in every two seconds by ms -1

Transcription

1 Acceleration Q I Choose the correct answer 1. If a body moves with uniform velocity its acceleration is -----zero. 2. Acceleration of a body is the rate of change of ----velocity 3. The acceleration of a body is 3 ms -2. This means that the velocity changes in every two seconds by ms The velocity time graph implies that the body A physical quantity having both magnitude and direction is ----acceleration. Q II Fill in the blanks 1. The S.I unit of acceleration is -----ms The negative acceleration is called ---deceleration 3. If a body comes to a stop, its final velocity is ---zero 4. The velocity gained in 5 seconds by a body moving with uniform acceleration of 1 ms -2 is ---5 ms A scalar quantity has only---magnitude Q III Match the following A B 1. Equal change in position uniform motion

2 2. Unequal change in position non- uniform motion 3. Increase in velocity acceleration 4. Decrease in velocity deceleration 5. Equal change in velocity uniform acceleration Q IV Answer the following 1. State the difference between uniform and non-uniform motion Ans If a body changes its position equally at equal intervals of time it is said to be uniform motion. If a body changes its position unequally at equal intervals of time it is said to be non-uniform motion 2. Define acceleration with an example. Ans The rate of change of its velocity is acceleration. Eg. An elevator lift just starts to move from first floor to fifth floor. 3. Distinguish between acceleration and deceleration. Acceleration Change in velocity with reference to time is acceleration Deceleration decrease in velocity over over the time is deceleration 4. What is meant by uniform acceleration? State its units. Ans Uniform acceleration of a body is the change in velocity by equal amounts in equal interval of time. Its unit is ms Explain the term deceleration with an example. Ans Deceleration is the negative acceleration where the velocity of a body decreases over the time interval. Eg. Consider a vehicle race. When race is over it cross the closing line and tend to attain rest.

3 6. Calculate the acceleration of a body if it starts from rest and attain the velocity 20 ms -1 in 10 second. Ans Initial velocity = 0 Finial velocity = 20 ms -1 t= 10 sec Acceleration =? a= v-u t a = = a= 2 ms An object moving at a velocity 24ms -1 is brought to a halt in 8seconds by applying a force in opposite direction to the motion. Calculate the acceleration. A initial velocity = 24m/s Final velocity = 0 Time = t = 8s a= v-u t a = = = - 2.5m/s 2

4 8. If a vehicle is accelerated to 5 ms -2 how much time does it takes to attain a velocity of 27 ms -1 which initially starts with 2ms -1? a= 5ms -2 u= 2 ms -1 v= 27 ms -1 t =? a= t= t= t= = 5 sec 9. What does it imply and why? If a) Acceleration of a body is zero m/s uniform acceleration b) Initial velocity of a body is zero m/s ---- at rest c) Final velocity of a body is zero m/s deceleration V Give reason 1 A car travelling on an uneven mud road is an example of non uniform motion. A Because on uneven mud road there is change in the position unequally in equal interval of time. 2 Acceleration and deceleration have the same units yet

5 they have difference. A Because the negative acceleration is called deceleration. ********************* Acids, Bases and Salts Q I Choose the correct answer 1. The one which is not an organic acid carbonic acid. a lactic acid b. acetic acid c. carbonic acid d. citric acid 2. Hydrochloric acid is used in purifying common salt. a. Purifying precious metals like gold. b refining petrol c. purifying common salt d preparing soft drinks 3. Caustic soda is not used in this industry cement Textile, rayon, soap, cement 4 The chemical used by farmers to neutralize acid content calcium oxide. Calcium oxide, Calcium hydroxide, Calcium carbonate Calcium chloride Q II Fill in the blanks 1. Vitamin C is chemically called ascorbic acid. 2. Mineral acids are also called acarbonic acid. 3. Bases that dissolve in water called alkalies. Q III Write the chemical names for the following

6 1. Common salt Sodium chloride 2. Caustic soda Sodium hydroxide 3. Washing soda sodium carbonate 4. Slaked lime Calcium hydroxide 5. Baking soda Sodium bi-carbonate 6. Epsom salt magnesium sulphate Q IV Match the following A B 1. Iactic acid milk 2. folic acid lettuce leaves 3. tannic acid tea 4. tartaric acid unripe mango 5. malic acid apple Q V Answer the following 1. What are organic acid? Ans. Acids that occur naturally are called organic acids. 2. Make a list of four physical properties of a) acids b) bases Ans Acids 1. Acids are sour to taste. 2 acids turn blue litmus paper red. 3 acid in water makes the solution conductive.

7 4 acids are corrosive. Bases 1 Bases are bitter in taste. 2 bases turn red litmus paper blue. 3 Bases are soapy to touch. 4 Solutions of bases are good conductor of electricity. 3. What are indicators? Give two examples. Ans Indicators are chemical substances to indicate if substance is acidic, basic or neutral. Eg methyl orange, phenolphthalein etc. 4. What is a neutralization reaction.? Ans The reaction of a base with an acid to form the respective salt and water is called neutralization reaction. 5. Mention two applications of neutralization reaction.? Ans 1 ) Bee stings are acidic. An application of baking powder, a base on sting area helps to neutralize and hence ease the pain and burning sensation on the skin. 2 )Farmers mix calcium oxide to acidic soil to neutralize the soil to make it fit to grow plants. 6. What is P H value? If the P H value of a substance is 13 what does it indicate? Ans A special scale used to measure the acidity or basic strength of substances. The P H value of a substance is 13 indicates that the substance is basic in nature. 7. A solution indicates seven on P H scale, what does this tells you about the solution? Ans A P H value of seven indicates that the given solution is neither an acid nor a base. It is neutral. 8. Write two uses of each of the following.

8 Hydrochloric acid 1. Used to manufacture glue. 2) To purify common salt. Sulphuric acid 1 ) To refine petrol. 2) In the manufacture of fertilizers, detergents, drugs, plastics, paints and chemicals. Caustic soda 1) To refine petroleum. 2) In the manufacture of rayon, medicine and paper. Slaked lime 1) In white wash 2) To remove fur from animal skin. Sodium chloride 1) To taste our food 2) Used in pottery glazing. Baking soda 1) In bakery products like bread and cakes. 2) In fire extinguishers. Washing soda 1) To wash clothes. 2) In the manufacture of caustic soda, borax, detergents, paper and glass. 9. Hydrogen is liberated when acid react with metals. Explain this with the help of an experiment. Ans Aim Hydrogen is liberated when acid react with metals. Apparatus---Test tube, stand, match stick, candle Chemicals Hydrochloric acid, magnesium wire Procedure Take dilute hydrochloric acid in a test tube and put 2or 3 pieces of magnesium wire into it. Bring a burning splinter near the mouth of the test tube. Will observe that splinter off with a pop sound. This shows that hydrogen gas liberated. 10. Explain the experiment the reaction of an acid with calcium carbonate with the help of a diagram. Ans Refer page no 95 figure 8.7 for figure Apparatus Test tube,funnel, stand, delivery tube Chemicals ---Calcium carbonate, hydrochloric acid,calcium hydroxide

9 Procedure - Take calcium hydroxide in a test tube Arrange the apparatus as shown in the figure. Pour dilute hydrochloric acid into the test tube through the funnel. A brisk effervescence is observed. This evolved gas passes into the lime water. The lime water turns milky. The gas evolved is carbon dioxide 11 Write an experiment to show the neutralization of a base with an acid. Ans Aim- To show the neutralization of a base with an acid. Apparatus : Burette, conical flask, stand, white tile Chemicals : Sulphuric acid, sodium hydroxide, Phenolpthalein Procedure: Take about 10 ml of sodium hydroxide in a conical flask. Using dropper add a few drops of Phenolpthalein and stair. It becomes pink in colour. Now add a few drops of dilute sulphuric acid using a burette and shake the flask. The pink colour of the solution fades. Add more drops of dilute sulphuric acidthe pink colour disappears. The resulting solution is called neutralized solution. For figure refer page no 102 Fig Make a list of four difference between the properties of acids and bases. Ans Acids Bases 1 Sour to taste Bitter to taste 2 Feel irritates/ burns soapy to touch skin 3 Turns blue litmus red Turns red litmus blue 4 corrosive some are corrosive 13 What is the importance of p H value in daily life.

10 Ans 1) The p H range within which the human body functions is 7 to 7.8.The human stomach produces hydrochloric acid to help digestion. An increase in this acid can be managed by taking antacid to neutralize the excess of acid. 2) If the p H value in the mouth falls below 6.5 the acidity increases causing tooth decay. This could be prevented by cleaning the teeth with tooth paste which is basic. VI What happens when : 1. a blue litmus paper is dipped in lime juice. Ans When a blue litmus paper is dipped in lime juice it turns to red. 2. Potassium reacts with sulphuric acid. Ans When Potassium reacts with sulphuric acid forms salt and liberate hydrogen. 3. Calcium reacts with sulphuric acid. Ans when Calcium reacts with sulphuric acid forms respective salt and liberate hydrogen. 4. Magnesium carbonate react with sulphuric acid. Ans When magnesium carbonate react with sulphuric acid forms salt. Magnesium carbonate + sulphuric acid > Magnesium sulphate +water +carbondioxide ( 5. A base reacts with an acid. Ans A base react with an acid to form salt and water. VII Give reason for the following 1. A person bitten by red ants experiences a burning sensation on the skin. Because insect inject an acid into the human body when they bite. 2. A drop of concentrated sulphuric acid on a piece of cloth creates a hole in it.

11 Ans Because acids are corrosive in nature. 3. Acids are not stored in metal containers. Ans Acids are not stored in metal containers. Because acids corrode metals like iron and aluminium. So they are safe to store in glass container. 4. All alkalies are bases but all bases are not alkalies. Ans Because bases that dissolve in water are alkalies, but all bases do not dissolve in water. So all alkalies are bases but all bases are not alkalies. ***************************