The Class 10 is an important year in a student’s life and Maharashtra State Board Science 1 is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 10 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 10 Science 1 Book syllabus.
1. What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Answer: Redox Reaction is the reaction when both oxidation and reduction occur simultaneously. Now, take the example given here:
Pass hydrogen gas over black copper oxide and get a reddish coloured layer of copper.In this action, when the positive charge of an atom or an ion increases or the negative charge is decreased, then it is called oxidation. Likewise, when the positive charge is decreased or the negative is increased, then it is reduction. Take the equation, Cu0 + H2 → Cu + H2 0
In this reaction, when an oxygen atom is removed from CuO (copper oxide), then reduction of copper oxide takes place, whereas the hydrogen molecule takes up oxygen atom forming water (H2 O). Here, oxidation of hydrogen takes place. In this reaction, oxidation and reduction takes place simultaneously. Here, the reductant is oxidized by the oxidant, while the reductant reduces the oxidant. Because of the characteristics of the reduction and oxidation reactions, the single term ‘redox’ is used as an alternative to two terms. Thus, Redox Reaction= Reduction + Oxidation.
2. Explain endothermic reaction. Give an example.
Answer: When the heat from outside is absorbed during some physical changes such as melting of ice or dissolution of potassium nitrate in water, it is called ‘Endothermic processes.’ During the process of endothermic chemical reactions heat is either absorbed from the surroundings or has to be supplied continuously from outside.
CaCO3 (s) + heat → CaO (s) + CO2 (g) (Endothermic Reaction)
3. What is a catalyst?
Answer: Catalyst is the substance in whose presence the rate of a chemical reaction changes, without causing any chemical change to it. The decomposition of hydrogen peroxide into water and oxygen normally takes place slowly at room temperature. However, when we add manganese dioxide (MnO2) Powder in it, the same reaction increases speed. No chemical change takes place in MnO2 in this reaction. Hence, manganese dioxide (MnO2) Powder is the catalyst here.
4. Explain the term balanced equation.
Answer: In any reaction, as per the law of conservation of mass, the total mass of each of the elements in the reactants is equal to the total mass of each of the respective elements in the products. If the number of atoms of the elements in the reactants of the equation and the number of atoms of those elements in the products is the same, then it is a ‘balanced equation’. If the number of atoms of each element is not the same on the two sides of an equation, it is an ‘unbalanced equation’.
A chemical equation is balanced step by step.
This is the way in which a balanced equation is obtained from an unbalanced equation adapting proper factors to the appropriate reactant/product in order to balance the number of each element in steps.
5. When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky. Give scientific reason.
Answer: The gas formed on heating calcium oxide is carbon dioxide, which, when passed through freshly prepared lime water generates insoluble calcium carbonate and water in this reaction. The calcium carbonate turns the lime water milky.
Ca (CH)2 + CO2 ➡CaCO3 +H2 O
6. What is a displacement reaction?
Answer: During displacement reaction, the place of the ion of a less reactive element in a compound is taken by another more reactive element by formation of its own ions.
7. What are the factors affecting the rate of a chemical reaction?
Answer: The same reaction takes place at a different rate under altering the conditions. Given below are the factors that decide the rate of a chemical reaction:
(a) Nature of a reactant –the nature of the metal influences the rate of reaction. For example, Aluminium is more reactive than zinc.
(b) Size of the particles of the reactants- the rate of a reaction is dependent upon the size of the particles of the reactants participating in the reaction. That is, if the reactant particles are of smaller size, then the rate of the reaction will be higher.
(c) Concentration of the reactants- rate of reaction is proportional to the concentration of reactants. That is concentrated acid reacts faster than dilute acid.
(d) The temperature of the reaction- rate of the reaction increases with increase in temperature
(e) Catalyst- some reactions require a catalyst to speed up the reaction
8. What is a chemical reaction?
Answer: A process in which some substances undergo bond breaking and are transformed into new substances by formation of new bonds is called chemical reaction. The substances that undergo chemical reaction are called reactants, whereas the substances produced as a result of a chemical reaction by formation of new bonds are called products. A chemical reaction is represented by writing a chemical equation.
9. What is a double displacement reaction?
Answer: During a double displacement reaction, the ions in the reactants are exchanged to form a precipitate.
10. What is the physical change and chemical change?
Answer: Modifications that are prominent, resulting from the change in parameters such as temperature, pressure and so on. These changes are known as physical change and it is reversible. Meanwhile, the composition of water remains constant in the physical change. Take the example of ice transformed into water on heating and water is transformed into ice on cooling. If the composition of matter changes during a process, then it is called a chemical change.
11. Take a small amount of hydrochloric acid in a test tube. Heat the test tube. Dip a glass rod in the ammonia solution and hold on the top of the test tube. You will observe a white smoke emanating from the tip of the glass rod. Why?
Answer : On heating, HCL vapours emanate from the test tube and NH3 gas is generated from the solution on the glass rod. The ammonia gas and hydrogen chloride gas react together to form the salt ammonium chloride in gaseous state first. However, immediately because of the condensation process at room temperature, it is converted into a solid state, thus causing the white smoke. The chemical equation for this is as follows.
NH3 (g)+ HCl(g) ➡NH4 Cl(s)
Ammonia + Hydrogen chloride ➡Ammonium chloride
12. What is a combination reaction? What is decomposition reaction?
Answer: In a combination reaction, two or more reactants combine in a reaction to form a single product. Meanwhile, decomposition reaction is the reaction in which there is only one reactant giving rise to two or more products.