Question

class 10th science notes chapter 1​

Answer 1

Answer:

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Answer 2

$\large{\mathfrak\red{Chemical \:Reactions \:And \:Equations}}$

Whenever lime is mixed with water we get a clear solution with and on touching the tube it feels hot. That is lime when mixed with water undergoes certain physical changes that makes it evolve heat and give a clear solution.

Similarly, the iron articles undergoes physical changes and develops a layer of rust on its surface. It reacts with the oxygen present in air and moisture and develops rust (hydrated iron (III) oxide).

Chemical reaction

Whenever a chemical reaction takes place following changes occurs:

Change in colour

During rusting the iron articles undergoes change in colour. We have also observed that silver gets tarnished when kept for a long time. The metallic silver reacts with hydrogen sulphide or sulphur present in air and gets tarnished.

Change in state

On heating liquid changes its state and converts to vapour due to reaction within the particles caused by heat.

Change in odour

Due to chemical reaction food gets spoiled and smells really bad.

Change in temperature

Lime when mixed with water undergoes certain physical changes that makes it evolve heat and give a clear solution. Such reactions are called exothermic reactions.

Releases of gases

During Aerobic cellular respiration in human body energy molecules combines with inhaled oxygen and releases energy needed by the cells. It also releases carbon dioxide gas and water.

Chemical equation

Describing all of the chemical reactions that occurs around us in words is quite impossible.

Iron on reacting with oxygen and water present in atmosphere undergoes chemical transformation and gets converted to ferric oxide i.e. Rust.

Balanced chemical equation

It is always necessary to balance a chemical equation. In an unbalanced equation the mass is not the same on both sides of the equation which leads to violation of law of conservation of mass which states that mass can neither be created nor destroyed. So balancing a chemical equation balances the amount of reactant and product on both side of arrow. An unbalanced chemical equation is called a skeletal chemical equation.