1. At present about 118 elements are known.
2. Elements can be divided into two main groups: metals and non-metals.
3. Elements which form positive ions by losing electrons are called metals. Thus, metals are the elements which have the tendency to lose electrons.
In this video and subsequent videos, we will focus on Acids and its properties. We'll learn about
- What are Acids?
- What is the role of acid in our life?
- How acids are classified?
Q1: What is the atomic number of a carbon atom?
Answer: 6
Q2: How many valence electrons are present in a carbon atom?
Answer: 4 (electronic configuration is K:2 L:4)
Q3: What are allotropes?
Answer: The property due to which one element exists in more than one form, which differs in physical properties but has similar chemical properties. These forms of an element are called allotropes.
Q1: All metals are solids except:
(a) Sodium
(b) Calcium
(c) Mercury
(d) Copper
Q2: Which of the following metal does not react with dilute Hydrochloric acid?
(a) Iron
(b) Sodium
(c) Magnesium
(d) Copper
Fill in the blanks with suitable words
1. An acid is a compound which when dissolved in water gives _________ ions as the only _________ ions.
2. Higher the pH value of a solution, the more __________ it is.
3. pH value of lemon juice is _________ than 7.
Salts/Compounds Colour
1. Potassium dichromate, K₂Cr₂O₇ Orange
2. Potassium permanganate, KMnO₄ Violet
3. Ferric tetra-oxide, Fe₃O₄ Black
4. Ferrous sulphate, FeSO₄.7H₂O Green
5. Ferric sulphate, Fe₂(SO₄)₃ Yellow
6. Ferric hydroxide, Fe(OH)₂ Green
Assertion and Reasoning based questions are a bit tricky. You should be able to distinguish whether the assertion is well connected to the reason or these are just random facts. Read both statements carefully, and check if both statements are factually or logically correct or not. If both are correct, then try to check if both are well connected to each other or not.
The questions below consist of statements of an Assertion and a Reason. Use the following key to choose an appropriate answer:
Based on chemical properties, all compounds can be classified as acids, bases and salts. To identify acids and bases, indicators are used. This video talks about types of indicators i.e. natural, synthetic and olfactory. Examples of indicators and related questions are also covered.
The first chapter of Chemistry talks about chemical reactions and equations. In a chemical reaction, reactants are transformed into products. In this series, the part-4 video discusses:
- corrosion
- examples of corrosion (good vs bad)
- methods to prevent corrosion
- rancidity
- methods to prevent rancidity
Learning is a continual process. To improve scores, the best way is to learn and practice. Solving question papers help students to evaluate their knowledge and familarise with different types of question patterns being asked in the examination.
Eduvictors provides CBSE Previous Year Papers and Sample Question Papers for Class 10 Maths, Science, Social, English, Hindi and Sanskrit with/without solutions to help students in their board exam preparation.
1. Buy CBSE All In One Science Class 10 for 2021 Exam
Here attached the Chemistry Sample Question Paper (2020-2021) for your self-evaluation.
1. Why does not a wall immediately acquire a white colour when a coating of slaked lime is applied on it ?
2. Define displacement reaction with one example.
3. Identify the most reactive and least reactive metal : Al, K, Ca, Au.
4. Which of the following is a combination reaction and which is a displacement reaction ?
(a) Cl₂ + 2KI ——–> 2KCl + I₂
(b) 2K + Cl₂ ——–> 2KCl.
5. What is the difference between the following two reactions ?
(a) Mg + 2HCl ——–> MgCl2 + H2
(b) NaOH + HCl ——–> NaCl + H2O.
6. Identify the compound which is oxidised in the following reaction
H₂S + Br₂ ———–> 2HBr + S.
7. What happens chemically when quick lime is added to water ?
Q1. A green layer is gradually formed on a copper plate left exposed to air for a week in a bathroom. What could this green substance be?
Answer. It is due to the formation of basic copper carbonate [CuCO₃.Cu(OH)₂].
Q2. Why are elements of Group IA i.e. H, Li, Na, K, Cs and Fr called alkali metals?
Answer. Because oxides of these elements dissolve in water to give alkali or soluble hydroxides.
Q3. A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
Answer. ‘X’ is carbon, ‘Y’ is diamond as it is the hardest natural substance and ‘Z’ is graphite as it is good conductor of electricity.
The first chapter of Chemistry talks about chemical reactions and equations. In a chemical reaction, reactants are transformed into products. In this series, the part-3 video discusses types of chemical reactions.
Following questions are covered:
Q1: What are the important types of chemical reactions.
Q2: What are combination reactions? Give examples.
Q3: Hydrogen burns in oxygen to form water. Identify the type of reaction.
CBSE Class 10 - Chemistry
Chapter: Acids and Bases
Q1: How is the strength of acid and base can be estimated?
Answer: Strength of acid and base can be estimated by using universal indicator.
Q2: What is a universal indicator?
Answer: Universal indicator is used to estimate the strength of an acid or a base. It is a mixture of several indicators. It shows different colours at different concentrations of H⁺ ions in the solution.
Q3: What is pH value of a solution?
Answer: The pH of a solution is inversely proportional to the concentration of hydrogen ions in it. Mathematically the pH of a solution is inversely proportional to the concentration of hydrogen ions in it. pH is a pure number, it has no units.
The first chapter of Chemistry talks about chemical reactions and equations. In a chemical reaction, reactants are transformed into products. In this series, the part-2 video covers questions and answers about the definition of chemical equation. Understand the difference between unbalanced and balanced chemical equations. Why balancing of chemical equation is necessary? Steps involved in balancing a chemical equation.
