Q2. Are the melting point of the solid state and the freezing point of the liquid state of a substance different.
(Ans) No, these are the same.
For example, melting pt. of ice = 0oc or 273K
and freezing pt. of water = 0oc or 273K
Q3. A certain substance ‘A’ cannot be compressed but takes up the shape of any container in which it is placed. What is the physical state of 'A'?
(Ans)As the substance'A'has fixed volume but lacks a fixed shape,it is liquid.
Q4. A rubber band changes its shape when stretched. Can it be regarded as solid?
(Ans)Yes, it can be regarded as solid. A rubber band undergoes a change in shape on stretching i.e. on applying pressure. When the pressure is released, it regains its original shape. Such solids are known as elastics.
Q5. What are volatile liquids?
(Ans)Liquids having low boiling points are known as volatile liquids.
Q6. Which scale of measuring the temperature is the best?
(Ans) Kelvin scale is the best scale for measuring temperature as on Kelvin scale, all temperatures have positive values.
Q7. Define diffusion.
(Ans)Particles of one substance occupy the vacant spaces presentbetween the particles of the other substance.This is called diffusion.
Q8. Is matter continuous or particulate?
(Ans)Matter is not continuous, it is particulate in nature i.e. it is made up of particles.
Q9. What are the factors on which evaporation depends?
(Ans) Factors on which evaporation depends are -
C.Wind velocity D. Humidity
Q10. Define humidity.
(Ans)Humidity is the amount of water vapour present in air.
Q11. Define evaporation.
(Ans)The phenomenon of change of liquid into vapours at any temperature below its boiling point is called evaporation.
Q12. Why do the states of matter differ?
(Ans)The difference in various states of matter is due to the difference in the distances between the constituent particles.
Q13. Define melting point.
(Ans)The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
Q14. Write the full form of L.P.G. & C.N.G.
(Ans)L.P.G. - Liquefied petroleum gas.
C.N.G. - Compressed natural gas
Q15. Inspite of being solid, a sponge is compressible. Comment.
(Ans)A sponge has minute holes in which air is trapped. When we press it, the air is expelled out and the sponge gets compressed.
Q16. Define matter.
(Ans)Anything which occupies space and has mass is known as matter.
Q17. What produces more severe burns, boiling water or steam?
(Ans)Steam produces more severe burns than boiling water due to its high latent heat .
Q18. Arrange the following substances in increasing order of force of attraction between the particles - water, sugar and oxygen.
(Ans) The arrangement in the increasing order of intermolecular force is-Oxygen < Water < Sugar.
Q19. Suggest a method to liquify atmospheric gases.
(Ans)Atmospheric gases canbe liquified by lowering its temperature and increasing pressure simultaneously.
What are the factors that determine the state of a substance?
Q 20.What are the factors that determine the state of a substance?
Pressure and temperature determine the state of a substance, whether it will be solid, liquid or gas.
Q 21. Why does our palm feel cold when we put some acetone, petrol or perfume on it?
(Ans) When we put some acetone, petrol or perfume on our palm, the particles of these substances absorb energy from the palm or surroundings andvaporize causing cooling. Hence, our palm feels cold.
Q 22. Liquids generally have lower density as compared to solids. But ice floats on water. Why?
(Ans) In ice, water molecules form hydrogen bonds and form cage like structure. Due to cage like structure air gets entrapped. Due to this, ice has less density than water & floats on water.
Q 23 Why do we sweat on a humid day?
(Ans)During a humid day, the air around us has already high percentage of water vapours. Therefore, the water coming from the skin gets less opportunity to change into vapours and remains sticking to our body, we therefore sweat on a humid day.
Q24. Why do solids generally lack the property of diffusion?
(Ans)In solids, the particles are very closely packed and possess very low kinetic energy. Hence, they lack the property of diffusion.
Q25. How will you demonstrate that air contains water vapours?
(Ans)Take a dry glass beaker and fill it with some crushed ice. After sometime, droplets of water are observed on the outer surface of glass. This is because ofcondensation of water vapours present in air. When water vapourscome in contact with the glass surface where the temperature is very low, they change into water droplets.
(Q.1) Name the force due to which a body performs circular motion.
(Ans)A body performs circular motion due to centripetal force.
(Q.2) What is the nature of gravitational force?
(Ans)Gravitational force is always attractive in nature.
(Q.3) What is the numerical value of gravitational constant?
(Ans) The numerical value of gravitational constant is 6.7 X 10–11 N m2 kg–2
(Q.4) Define thurst.
(Ans) Force perpendicular toany surface is called thrust.
(Q.5) Name the force experienced by the body when it is immersed in a liquid.
(Ans)Buoyant force is experienced by the body when it is immersed in a liquid.
(Q.6) What do you mean by the weight of the body?
(Ans)The weight of the body is the force with which the earth attracts it in downward direction
(Q.7) What is the acceleration of free fall?
(Ans)If a body falls freely then it will fall with an acceleration which is equal to acceleration due to gravity. Its value is 9.8m/sec2
(Q.8) What is the weight of an object on moon?
(Ans)The weight of an object on moon is 1/6 times its weight on earth.
(Q.9) Why the cutting edge of a knife should be as sharp as possible?
(Ans)The cutting edge of a knife should as sharp as possible so as to have greater pressure even for a very small applied force for quick action.
(Q.10) Iron nails sinks in water.Why?
(Ans)The density of an iron nail is more than the density of water. This means that the upthrust of water on iron nails is less than the weight of the nail. So it sinks.
(Q.11) Explain, why the value of ‘g’ is greater at poles than at equator.
(Ans)The earth is not a perfect sphere. As the radius of the earth increases from the poles to the equator, the value of ‘g’ becomes greater at the poles.
(Q.12) Why does a truck or motor-bus has much wider tyres?
(Ans)A truck or motor bus has wider tyres so that the pressure acting on the road due to weight of the truck may be small.
(Q.13) What do you mean by force of buoyancy?
(Ans)When a body is completely or partially immersed in a fluid, then the upward thrust acting on the body is called force of buoyancy.
(Q.14) State Archimedes’ principle.
(Ans)Archimedes’ principle states that when a body is immersed partially or fully in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.
(Q.15) The density of gold is 19.3X103kg/m3.Find its relative density.
(Q.16) Explain why moon moves around earth.
(Ans)The moon moves around the earth due to the centripetal force. The centripetal force is provided by the earth`s gravitational force of attraction.
(Q.17) A stone is dropped from the top of a building of height 45 m. Calculate its velocity , when it srtikes the ground.(Take g=10 m/s2)
(Ans) Given ,height(h) of the building is 45 m and g=10 m/s2 When the stone is dropped, initial velocity ,u=0. let final velocity be v. Applying equation, v2 = u2 +2gh or,v2 = 0+2x10x45 or, v =900 m/s=30 m/s.
Why do we fall ill
(Q.1) Write the name of the organism that causes kala-azar.
(Q.2) What is a disease?
(Ans) Disease means being uncomfortable.
(Q.3) Write one example of both infectious and non-infectious disease?
(Ans) Cholera and blood pressure
(Q.4) Which type of disease is more dangerous for the health?
(Ans) Chronic disease
(Q.5) What happens if the body is suffering from disease?
(Ans) If body is suffering from disease, one or more organs of the body will not work and cause the worst condition.
(Q.6) Which organism is responsible for causing malaria?
(Q.7) What are vectors?
(Ans) The organisms, which carry infectious agents from one person to the other person,are called vectors.
(Q.8) Define health.
(Ans) ‘Health’ is a state of complete well being (Physical mental and social ) and not merely freedom from diseases.
(Q.9) Name four diseases for which vaccines are available.
(Ans) (i) Tetanus
(iii) Whooping cough
(Q.10) What is the difference between acute and chronic diseases?
(Ans) Such type of diseases, which last for only very short period of time are called acute diseases, e.g., common cold but when the diseasespersist for a longer period, it is called chronic diseases, e. g., elephantiasis.
(Q.11) How does community health depend on personal health?
(Ans)Social equality and harmony in the community are important to maintain individual’s health and vice-versa, the health of the whole community depends on the personal habits of various individuals who constitute the community.
(Q.12) How does AIDS virus spread?
(Ans)The HIV virus can spread through:
- Sex with HIV infected person.
- Blood transfusion
- Shared needles
- HIV positive mother to her child.
(Q.13) Why the making of antiviral medicines is harder than antibacterial?
(Ans)The viruses have few biochemical processes of their own. They enter our cells and use machinery for their life processes. This means that there are few viruses where specific targets to aim needs to be done.
(Q.14) Why penicillin affects only bacteria not human cells?
(Ans)The antibiotic penicillin blocks the bacterial processes that build the cell wall. As a result, the growing bacteria become unable to make cell walls, and die easily. Human cells don’t make a cell wall anyway, so penicillin cannot have such an effect on us.
(Q.15) What is the general way to prevent infections?
(Ans)The general way of preventing infections mostly relate to preventing exposure. (i) For air-borne infection, overcrowded conditions are to be avoided. (ii) For preventing water-borne infections, one should use the safe drinking water only. (iii) For vector-borne infections, breeding of the vectors should be prevented by keeping the environment clean.
(Q.16) Give some symptoms of Hepatitis?
(Ans)Hepatitis produces an initial “acute phase. If there are symptoms, they tend to mimic "flu-like" symptoms such as: - mild fever - muscle or joint aches - nausea - vomiting - loss of appetite - slight abdominal pain - diarrhea - fatigue
(Q.17) Define the basis of principle of immunization.
(Ans)When the immune system first sees an infectious microbe, it responds against it and then remembers it specifically. So the next time that particular microbe, or its close relatives enter the body, the immune system responds with even greater vigour. This eliminates the infection even more quickly than the first time around. This is the basis of the principle of immunization.
(Q.18) Explain how HIV-AIDS virus affects and damages our body?
(Ans)In HIV infection, the virus goes to the immune system and damages its function by attacking cells of the immune system (T-cells). Gradual decrease in their number weakens our immune system. Our body is then no longer able to fight against various diseases and becomes susceptible to them
(Q.19) Name the causal organisms of Diarrhoea. Write its symptoms and preventive measures.
(Ans)E. coli, Shigella sp., protozoa, viruses and nematodes. Symptoms – Frequent loose motions, vomiting leading to dehydration, weight loss, weak pulse, deep breathing and fever. Preventive measures – eatables should be covered fruits and vegetables should be washed properly, personal hygiene and community hygiene are important
(Q.20) What is immunization? Who discovered it? Name the disease against which it was discovered.
(Ans)Immunization, or immunisation, is the process by which an individual is exposed to an agent that is designed to fortify his or her immune system against that agent. Edward Jenner discovered it. He discovered it against smallpox.
(Q.21) How does malaria spread? What is the mode to treat disease?
(Ans)It is caused by protozoan parasite Plasmodium. This disease spreads through the bite of an insect vector- the female Anopheles mosquito, which feeds on human blood. A drug, quinine is used to treat a person suffering from malaria.
(Q.22) What are the causes, symptoms and the methods of the prevention of tuberculosis?
(Ans) Tuberculosis or TB, is a contagious disease of the lungs that can spread to other parts of the body and may be fatal. TB is caused by a microorganism known as the tubercle bacillus, or Mycobacterium tuberculosis. A person with tuberculosis disease may have some of the following symptoms: - A cough that will not go away - Feeling tired all the time - Weight loss - Loss of appetite - Fever - Coughing up blood - Night sweats Preventive measures include strict standards for ventilation, air filtration, and isolation methods in hospitals, medical and dental offices, nursing homes, and prisons. If someone is believed to have been in contact with another person who has TB, preventive antibiotic treatment may have to be given. Infected persons need to be identified as soon as possible so that they can be isolated from others and treated.
(Q.23) Do all microbes go to the same organ or tissue or they go to the different organs? If they go to different organs how do they damage it?
(Ans)Microbes do not affect the same organs but different organs. Microbes have various pathways to affect the human body as mouth, nose, blood, etc. If they enter from the air via nose, they are likely to go to the lungs, e.g., tuberculosis. If microbes enter through the mouth, they can stay in gut lining, e.g., typhoid. But when the infection takes place like AIDS, it will spread all over the body. Malaria causing microbes entering through a mosquito bite, will go to the liver and then to the red blood cells. The virus causing encephalitis or brain fever, will similarly enter through a mosquito bite, but it goes on to infect brain.
(Q.24) What is immunity and immune system? Give the factors, which cause reduction in immunity of the body?
(Ans)The body’s ability to resist and overcome infection is called immunity. The immune response varies from person to person and so some persons are more sensitive to infection than others. An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects a wide variety of pathogens, such as viruses and parasitic worms and distinguishes them from the organism’s normal cells and tissues. Detection is complicate as pathogens adapt and evolve new ways to successfully infect the host organism. Factors, which affect the immune system are: - Becoming exposed to the highly infectious organisms. - Unavailability of proper and sufficient food.