PAF Chapter Comprehensive Worksheet May 2016 Science Class 7 (Answering Key)

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1 The City School PAF Chapter Comprehensive Worksheet May 2016 Science Class 7 (Answering Key) The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 1 of 7

2 OBJECTIVE [ /50] Q.1 Encircle the best answer from the given options. [ /30] 1.Size of an animal cell is Smaller than plant cell 2.The thread like structure present in the nucleus chromosomes 3.They are made up of proteins called DNA Genes and chromosomes 4.The characteristics of an organism are passed down from one generation to the next by genes 5.Function of nucleus is Both of the above 6.These substances can change from solid to vapours form directly without melting All of the above 7.The particles in a solid can Vibrate on their fixed positions 8.Physical change can bring about the change in The state of a substance 9.Diffusion is the movement of particles from an area of Higher concentration to lower concentration 10. This gas is poisonous and brown in colour Bromine 11. A chemical formula shows The NO. and kinds of atoms in a molecule 12. Which of the following substances consist of two different kinds of atoms chemically combined together? KCl 13. Molecules of an element are made up of atoms of the same element 14. Which of the following instruments can be used to look at atoms? electron microscope 15. These are pure substances elements and compounds 16. Scientific word used for burning is combustion 17. When Magnesium burns in air, it forms a white solid called Magnesium oxide 18. Natural gas, a fossil fuel is made up mostly of the compound called methane 19. A chemical reaction in which a substance breaks down into two or more simple substances is called decomposition 20. Formation of ice from water is due to Freezing The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 2 of 7

3 21. Substances that burn and release energy are called fuels 22. When the air holes of a Bunsen burner are closed it gives out Luminous flame 23. Crude oil extracted from the ground is a sticky black liquid, different substances are separated from it by a process called fractional distillation 24. The 3 R S means Reduce, reuse, recycle 25. To use energy and avoid wasting it is called Conservation of energy 26. In an electrical motor electrical energy is converted into Sound and mechanical energy 27. In an electrical bulb, electrical energy is converted into Heat and light energy 28. when a battery is used up and goes flat what is used up? energy 29. in a parallel circuit when more resistors are added, its resistance decreases 30. in a closed circuit electrical current flows from positive to negative terminal The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 3 of 7

4 Q.2 Fill in the blanks with suitable answers. [ /5] 1. permanent 2. physical 3. Thermal decomposition 4. Hydrogen, carbon dioxide 5. conserved Q.3 State true or false. Write correct statement for a false one. [ /10] 1. False. cell membrane is semi permeable. 2. False. In animal cell, cell division starts from the nucleus towards cytoplasm(from inside to outside of cell),in plant cell, cell division starts from outside that means from cytoplasm towards the nucleus 3. False. John Dalton observed 4. False. Solid particles 5. False. When an atom gains or loses electrons 6. False. The gases which exist in atomic state are called as noble gases or inert gases. 7. False. Biomass is an example of renewable energy resource. 8. False. Crude oil was formed underground when plankton died and got buried underground. 9. False. A switch is used to open or close a circuit. 10. False. The current flowing through each component in a series circuit is same everywhere. Q.4 Give scientific reasons. [ /5] 1. Plant cells can make their own food because they have chloroplasts in them. 2. Solids cannot flow because their particles are tightly packed together. 3. A chlorine atom has 17 electrons in it, while a chloride ion has 18 electrons in it because chloride ion is formed when chlorine atom gains one electron. 4. When we burn fossil fuels they cause air pollution because carbon dioxide gas is produced by burning them. 5. An electrical circuit does not work when the switch is open because then the circuit is broken, connections are not complete. The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 4 of 7

5 SUBJECTIVE [ /50] Q.1 (a) - Differentiate between an animal cell and a plant cell. [ /4] Part of cell Animal cell Plant cell Size of cell Smaller than plant cell Bigger than animal cell cytoplasm Filled in the entire animal cell Just like a thin layer, due to a large vacuole in the centre of cell vacuole Small, numerous, scattered in the cell Single, large, central vacuole Shape of cell Irregular in shape, somewhat like a tiny bag Regular in shape due to cell wall, some what like a tiny box (b) Complete the table. [ /4] Part of a microscope Its function stage Specimen slide is kept here mirror reflects light to make the specimen visible Stage clips Hold the slide in place Objective lens Magnifies the object / specimen Q.2 (a) Define the following terms. [ /5] Diffusion: movement of particles from higher to lower concentration area Brownian motion: haphazard(random), constant motion of particles Sublimation: change of state from solid to gas and from gas to solid, directly Density: mass per unit volume a substance The particle model of matter: atom is a tiny, discrete particle, matter is made up of particles (b) Choose the name of the scientist from the box given below and write with his work. [ /5] Scientist Robert Brown John Dalton Albert Einstein Democritus Aristotle His work in the development of Particle Model of Matter. Observed some pollen grains suspended in water were constantly moving about randomly in all directions Suggested that matter is made up of small discrete particles which are like little solid balls Explained that the dead pollen grains were moving because they were being bombarded by the moving water particles Hypothesized that matter is made up of tiny discrete particles called atoms which are too small to be seen Hypothesized that matter has a continuous composition that can be broken down into smaller and smaller pieces The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 5 of 7

6 Q.3 (a) Name the fossil fuels. Why are they called as non- renewable resources of energy? [ /3] Crude oil, natural gas and coal. Because once they are used they are finished, formed after millions of years. (b) Why is the Sun, the main source of almost all the energy resources on the earth? [ /3] Because plants make their food by using sun s energy, some animals eat plants to get their energy, some animals eat other animals to get their energy, when plants and animals died and got buried underground they changed into fossil fuels after millions of years, so the Sun is the main source of almost all the energy resources on the earth. (c) Describe Geo thermal energy. [ /2] Earth is hot from inside (its core), at certain points this heat is closer to the surface of the earth, it heats up the water under the earth s surface. When that hot water comes out in form of hot fountains/springs,, this steam of hot water can be used to turn turbines to generate electricity. Q.4 (a) Differentiate between: [ /4] Atom Smallest, discrete particle of matter Molecule of element It is made up of two or more atoms, all of the same kind, joined together Ion It is formed when an atom gains or loses an electron Molecule of compound It is made up of two or more atoms, all of different kind, combined chemically together (b) For the following elements, write down the symbols of their atoms and ions. [ 4] Name of the element symbol of its atom symbol of its ion Sodium Na Na+ Aluminium Al Al3+ Chlorine Cl Cl- calcium Ca Ca2+ Q.5 (a) Differentiate and give examples. [ /4] Physical change Change of state only No new substance formed No chemical reaction happens Can get previous substances back Chemical change Change of nature of substance new substance formed chemical reaction happens Cannot get previous substances back (b) Chemical reactions are of different types. Write one word equation for each of the following types of chemical reaction. [ /3] (1) Combination reaction: Sodium+ Chlorine Decomposition reaction: Sugar Combustion reaction; Sodiumchloride carbon+ water(vapour) The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 6 of 7

7 Magnesium+ oxygen Magnesium Oxide (c) Which gas is given off when Methane burns in air? [ /1] Carbon dioxide gas Q.6 (a) Sarah went out in darkness, she tried to switch on her torch but it did not work. Write the possible faults in her torch, which stopped it from working. [ /4] 1. Switch connections could be broken 2. Batteries might be wrong way or might be flat( finished) 3. Bulb could be fused(broken/not working) 4. Wires in the torch could be broken (b) Draw a series circuit and a parallel circuit using symbols. [ /4] Series circuit Use components and draw a series circuit of your own choice( single path for current flow) Parallel circuit Use components and draw a parallel circuit of your own choice ( more than one path for current flow) The City School/ PAF Chapter/ Comprehensive Worksheet/ May 2016/ Science/ Class 7 /Ans Key Page 7 of 7