Description : 11. Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface. [Delhi] -Chemistry-10
Last Answer : Answer. Light from different points on the pencil, immersed in water refracts and appears to come from a point above the original position.
Description : What happens when baking soda is heated? -Chemistry-10
Last Answer : Sodium hydrogen carbonate (also known as sodium bicarbonate or bicarbonate of soda) has the chemical formula NaHCO3. When it is heated above about 80°C it begins to break down, forming sodium carbonate, water and carbon dioxide. This type of reaction is called a thermal decomposition.
Description : Why is plaster of paris stored in a moisture proof container? -Chemistry-10
Last Answer : Plaster of Paris in contact with moisture (water) changes to solid hard mass, gypsum. Therefore, it gets wasted. Hence it should be stored in moisture proof containers.
Description : (i) Substances oxidised is Na as it gains oxygen and oxygen is reduced. (ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen. -Chemistry-10
Last Answer : During this reaction, the sodium is gaining oxygen and is being oxidized. Oxygen is getting reduced. During this reaction, copper oxide is losing oxygen and is being reduced. The hydrogen is gaining oxygen and is being oxidized.
Description : Identify the substances that are oxidised and the substances which are reduced in the following reactions. (i) 4Na(s) + O2(g) → 2Na2O(s) (ii) CuO (s) + H2(g) → Cu (s) + H2O(l) -Chemistry-10
Last Answer : (i) Substances oxidised is Na as it gains oxygen and oxygen is reduced. (ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen.
Description : Give an example of a double displacement reaction other than the one given in Activity 1.10 -Chemistry-10
Last Answer : Sodium hydroxide and hydrochloric acid react to form sodium chloride and water.
Description : An iron nail is dipped in the solution of copper sulphate for about 30 minutes. State the change in colour observed. Give reason for the change. -Chemistry-10
Last Answer : When an iron nail is dipped in copper sulphate solution, the displacement reaction takes place. The colour of copper sulphate solution fades due to the formation of light green solution of iron sulphate.
Description : Why does the colour of copper sulphate solution change when an iron nail is dipped in it ? -Chemistry-10
Description : Why is the amount of gas collected in one of the test tubes in text book Activity 1.7 (i.e., electrolysis of water) double of the amount collected in the other? Name this gas. -Chemistry-10
Last Answer : In Activity 1.7, water is electrolysed to give H2 gas at one electrode and O2 gas at the other electrode. 2H2O(l) → 2H2(g) + O2(g) Thus two molecules of water on electrolysis give two ... oxygen gas or in other words the amount of hydrogen gas collected would be double than that of oxygen gas.
Description : A solution of a substance ‘X’ is used for white washing. (i) Name the substance ‘X’ and write its formula. (ii) Write the reaction of the substance ‘X’ named in (i) above with water. -Chemistry-10
Last Answer : (i) The substance whose solution in water is used for white washing is calcium oxide (or quick lime). Its formula is CaO.
Description : Write a balanced chemical equation with state symbols for the following reactions : -Chemistry-10
Last Answer : (i) BaCl2 (aq) + Na2SO4 (aq) → BaSO4(s) + 2NaCl (aq) (ii) NaOH (aq) + HCl(aq) → NaCl(aq) + H2O(l)
Description : Write the balanced equation for the following chemical reactions. (i) Hydrogen + Chlorine → Hydrogen chloride (ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride (iii) Sodium + Water → Sodium hydroxide + Hydrogen -Chemistry-10
Last Answer : (i) H2 + Cl2 → 2HCl (ii) 3 BaCl2 + Al2(SO4)3 → BaSO4 + 2 AlCl3 (iii) 2Na + 2H2O → 2NaOH + H2↑
Description : Why should a magnesium ribbon be cleaned before burning in air ? -Chemistry-10
Last Answer : Magnesium gets covered with a layer of magnesium oxide when kept in air for a long time. This layer hinders the burning of magnesium. Hence, it is to be cleaned before burning.
Description : 15. An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the conve -Chemistry-10
Last Answer : Since, object-screen distance is double of object-lens separation, the object is at a distance of 2f from the lens and the image should be of the same size of the object.
Description : 14. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the -Chemistry-10
Last Answer : Answer. hope this helps you
Description : 13. A ray of light, incident obliquely on a face of a rectangular glass slab placed in air, emerges from the opposite face parallel to the incident ray. State two factors on which the lateral displacement of the emergent ray depends. [Foreign] -Chemistry-10
Last Answer : Lateral displacement depends on the: angle of incidence, thickness of slab, and refractive index of the material. (any two)
Description : 12. Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed: -Chemistry-10
Description : 10. Which kind of mirrors are used in the headlights of a motor-car and why? [Foreign] -Chemistry-10
Last Answer : Answer. Concave mirror, to get the parallel beam of light.
Description : 7. Redraw the given diagram and show the path of the refracted ray: [All India(C)] -Chemistry-10
Description : 6. “The refractive index of diamond is 2.42”. What is the meaning of this statement in relation to speed of light? [Delhi] -Chemistry-10
Description : 5. The refractive indices of four media A, B, C and D are given in the following table: -Chemistry-10
Last Answer : (i) Minimum change is seen as light moves between 1.50 and 1.52, i.e. B and C. (ii) Maximum change when light moves between 1.33 and 2.40, i.e. A and D.
Description : 4. If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. [Delhi (C)] -Chemistry-10
Last Answer : Answer. Ray NQ, as it has to be parallel to ray OS.
Description : 3. Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed: -Chemistry-10
Last Answer : Answer. Nature of image: Real, inverted and same size image is formed at the centre of curvature. Nature of image: Virtual, enlarged and erect image is formed behind the mirror. Nature of image: ... image: Virtual, erect and diminished image is formed between O and F on the same side of object.
Description : 2. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India] -Chemistry-10
Last Answer : this is the answer for the respected question
Description : 1. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. [Delhi] -Chemistry-10
Last Answer : Answer. hope this helps youu
Description : Giving a suitable example for each, explain the following : (i) Crystal field splitting (ii) Linkage isomerism (iii) Ambidentate ligand -Chemistry
Last Answer : i) Crystal field splitting: It is the splitting of the degenerate energy levels due to the presence of ligands. When ligand approaches a transition metal ion, the degenerate d-orbitals split into two ... the nitrogen atom or one of the oxygen atoms. Example : - SCN thiocyanate, - NCS isothiocyanate
Description : 6.What are metalloids? -Science
Last Answer : v Metalloids can be defined as chemical elements whose physical and chemical properties fall in between the metal and the non metal categories. Boron, germanium, silicon ... following elements are also known to be classified as metalloids in some circumstances:CarbonAluminiumSeleniumPoloniumAstatin
Description : How many of the following mimerals are oxides of metals// metalloids .
Last Answer : How many of the following mimerals are oxides of metals// metalloids .
Description : Elements that show the properties of both metals and non-metals are called (a) Allotropes (b) Metalloids (c) Alloys (d) Colloids
Last Answer : Ans:(b)
Description : Which is not a type of elements? (1) Metals (2) Non Metals (3) Metalloids (4) Gases
Last Answer : (3) Metalloids Explanation: Element is a chemical substance consisting of atoms having the same number of protons in their atomic nuclei. There are 118 elements that have been identified. The elements classified as metalloids are boron, silicon, germanium, arsenic, antimony, tellurium and polonium.
Description : Name all metalloids.
Last Answer : Ans: Si, Ge, As, Sb, Te, Po, At
Description : What do you mean by Metalloids? In which block metalloids are found?
Last Answer : Ans: elements showing some properties of metals and non metals both are called mettaloids .it are found in P block elements in BW 13 and 18 groups.
Description : What are metalloids? Give example.
Last Answer : Elements which are not distinctively metals and possess some physical properties of non- metals are called metalloids.
Description : What is Metalloids ?
Last Answer : Metalloids: Metalloids are the elements which possess both the properties of metal as well as non-metals. E.g. Silicon, Germanium, Antimony, etc.
Description : Metalloids (A) Are good conductor of heat & electricity (B) Act as electron donors with metals & as electron acceptor with non metals (C) Are not necessarily solids at room temperature ... & non-metallic properties to some extent and are exemplified by elements like germanium, silicon & boron
Last Answer : D) Are compounds that exhibit both metallic & non-metallic properties to some extent and are exemplified by elements like germanium, silicon & boron
Description : Define Metals , Non Metals & Metalloids.
Last Answer : Metals : 1. They are electropositive elements. 2. Their oxides are basic. 3. They tend to lose electrons & form positive ions. 4. They are lustrous , malleable & ductile except Hg which is the ... acidic ) in nature. 3. They are concentrated between the metals & the nonmetals in the periodic table.
Description : In known elements, the maximum number is of [CPMT 1985] (A) Metals (B) Non-metals (C) Metalloids (D) None of these
Last Answer : (A) Metals
Description : Metalloids
Last Answer : Metalloids or semi-metals have mostly non-metallic properties. One of their distinguishing characteristics is that their conductivity increases as their temperature increases. This is the opposite of what ... as computers. The metalloids include elements such as silicon (Si) and germanium (Ge).
Description : Metals, Metalloids and Non-metals
Last Answer : The elements in the periodic table can also be divided according to whether they are metals, metalloids or non-metals. The zigzag line separates all the elements that are metals from those that ... more metals then non-metals. Metals, metalloids and non-metals all have their own specific properties.
Description : 12.Few iron filings and a pinch of sulphur powder are taken in a china dish and mixed properly. Justify the change, giving two points as physical/chemical change. -Chemistry
Last Answer : It is a physical change as if we will bring the magnet near it all the iron fillings will attract towards it. Hence it shows the properties of it constituents are present so, no new substance is formed. Therefore, it is a physical change .
Description : Giving an example list two information which make a chemical equation more useful (informative). -Chemistry
Last Answer : (i) Physical state of reactants must be mentioned, e.g. 2H2 (g) + O2 (g)--- > 2H20 (l) (ii) Condition in which reaction takes place are written on the arrow head, e.g. ... BaCl2--> BaSO4 + 2NaCl (White ppt) The reaction is precipitation reaction. It is also called double displacement reaction.
Description : What is an ion? Explain the types of ion with examples. -Chemistry 9th
Last Answer : HI friend ... Atoms or Groups of atoms bearing charges are known as " ions ". The number of protons would not be equal to the no: of electrons , in an ion. There are two types of ... negatively charged. These ions take electrons from other elements to make itself stable. Examples : Cl⁻ , S²⁻
Description : Question 3: Explain the need for consumer consciousness by giving two examples. -Economics 10th
Last Answer : Two examples are Reji’s suffering and Amritha’s waiting. In case of Reji, a hospital, due to negligence of the doctors and staff in giving anaesthesia, crippled him for life. ... for appointment. Thus, there is a need for consumer consciousness to protect their interests successfully.
Description : “Power may also be shared among different social groups”. Explain by giving examples. -SST 10th
Last Answer : (i) Power may also be shared among different social groups such as the religious and linguistic groups. Community government' in Belgium is a good example of this arrangement. (ii) In some countries ... the' government. (iii) This method is used to give minority communities a fair share in power.
Description : ‘India is a federal country.’ Explain by giving examples. -SST 10th
Last Answer : (i) Division of powers : The Constitution demarcates the powers of the central and the state governments into different lists of subjects.There are three lists : (i) Union List. (ii) State ... central government, whereas land revenue, stamp duty, building tax, etc., come under the state government.
Description : “Federations are contrasted with unitary governments”. Explain by giving examples from Sri Lanka and Belgium. -SST 10th
Last Answer : Under the unitary system, either there is only one level of government or the sub-units are subordinate to the Central government. The Central government can pass on orders to the ... s not answerable to the Central government. Both these governments are separately answerable to the people.
Description : How is the Indian federal system different from that of Sri Lanka ? Explain by giving three examples. -SST 10th
Last Answer : (i) Sri Lanka believes in majoritarianism whereas in India equal rights are given to minorities. (ii) In Sri Lanka, Sinhala is the only official language, whereas in India though Hindi is the ... (iii) In Sri Lanka, the government protects and fosters Buddhism, whereas India is a secular country.
Description : The medal ceremony of 1968 Mexico Olympic became a historical landmark. Explain by giving examples. -SST 10th
Last Answer : (i) The incident provided a boost to the Civil Rights Movement in the United States. (ii) (a) The athletes tried to draw international attention to racial discrimination in the United ... ) Their action succeeded in gaining international attention for the Civil Rights Movement in the United States.
Description : “The focus on caste in politics can sometimes give an impression that elections are all about caste and nothing else. That is far from true.” Explain by giving examples. -SST 10th
Last Answer : (i) Constituencies are a mixture of people belonging to different castes : No parliamentary constituency in the country has a clear majority of one single caste. So, every candidate and party ... and communalism play a major role in politics, but elections are not about caste and communalism.
Description : ‘Industrialisation was a mixed blessing.’ Explain by giving examples. -SST 10th
Last Answer : (i) Cheap goods : The machine made goods were cheap and fine. So people of colonies could purchase cheap, fine and a variety of goods. (ii) New entrepreneurs : The process of industrialisation ... to compete with them. So along with the world market, they started losing the home market also.