Chemical Reaction & Equations Video Lecture - Science Class 10

0:0:0: hello and welcome to the first chapter
0:0:2: of our class 10th science series
0:0:4: chemical reactions and equations
0:0:7: life is chemistry every change we see
0:0:10: around us from cooking meals to the
0:0:12: simplest action of breathing is governed
0:0:14: by the laws of chemistry
0:0:16: we have already covered physical and
0:0:18: chemical changes of matter in our
0:0:20: previous classes
0:0:22: we have also studied that some changes
0:0:24: could be both physical and chemical
0:0:26: change simultaneously such as the
0:0:29: burning of a candle
0:0:32: every chemical change can be represented
0:0:34: by chemical reaction but first let's
0:0:37: study what is a chemical reaction
0:0:40: when we say a chemical reaction we talk
0:0:42: of chemical bonds which are broken
0:0:44: within the reactant molecules
0:0:46: accompanied by the formation of new
0:0:48: bonds
0:0:50: as a result new substances are formed as
0:0:52: products
0:0:54: to understand this further let's take an
0:0:56: example of a burning magnesium ribbon
0:1:0: when we lit a magnesium strip on fire we
0:1:3: observe that it burns with a dazzling
0:1:6: white flame and changes into a fine
0:1:8: white powder
0:1:10: this powder is magnesium oxide which is
0:1:13: also used for medical purposes as it
0:1:15: aids digestion
0:1:18: here the chemical reaction occurs
0:1:20: between magnesium and oxygen
0:1:23: thus we can conclude that a chemical
0:1:26: change has occurred if we observe
0:1:29: change in state
0:1:30: change in color evolution of a gas
0:1:33: and change in temperature
0:1:36: since now we know that a chemical change
0:1:38: is represented by a chemical reaction we
0:1:41: still need a convenient way to describe
0:1:44: them
0:1:45: for this purpose we use chemical
0:1:47: equations
0:1:49: taking the example we studied before
0:1:52: here is the word equation of that
0:1:54: chemical reaction
0:1:57: a word equation simply shows the change
0:1:59: of reactants to products which are
0:2:2: separated by an arrow with the reactants
0:2:4: on the left hand side and the products
0:2:6: on the right hand side
0:2:9: the arrow head point towards the
0:2:10: products and shows the direction of the
0:2:13: reaction
0:2:14: but there is an even better way to write
0:2:17: chemical equations by making use of the
0:2:19: chemical formulae and symbols
0:2:23: using this our equation becomes
0:2:26: mg plus o2
0:2:28: reacts to give mgo
0:2:30: you might have noticed that the number
0:2:32: of atoms of oxygen are lesser on the
0:2:34: product side than on the reactant side
0:2:37: and may wonder if this equation is
0:2:40: correct
0:2:41: since it seems to violate the law of
0:2:42: conservation of mass
0:2:44: well you are partially right and
0:2:46: partially wrong as here comes the topic
0:2:49: of balancing chemical equations
0:2:53: in our previous example we saw that the
0:2:55: number of atoms of each element were
0:2:58: different on either side of the arrow
0:3:1: such an equation is called an unbalanced
0:3:3: equation or a skeletal chemical equation
0:3:7: but this equation just gives an overview
0:3:10: of the reactants and products
0:3:13: it does not tell the actual amount of
0:3:15: each chemical compound involved
0:3:19: in the other case if the number of atoms
0:3:21: of each element are same on either side
0:3:24: of the arrow then the equation is called
0:3:26: a balanced chemical equation
0:3:29: we can understand this better with the
0:3:31: help of an interactive simulation
0:3:34: this simulation is a part of fed sim
0:3:36: simulation
0:3:38: we have our reactants on the left hand
0:3:40: side and products on the right hand side
0:3:43: we first count the number of atoms of
0:3:46: each element that are different on
0:3:48: either side of the arrow in the chemical
0:3:50: equation
0:3:52: let's start with nitrogen
0:3:55: for one molecule of nitrogen we have two
0:3:58: atoms of nitrogen on the right hand side
0:4:1: so we increase the number of ammonia
0:4:4: which is used as fertilizer in
0:4:6: agriculture
0:4:7: to two molecules
0:4:10: now the nitrogen atoms are balanced but
0:4:13: the hydrogen atoms are still unbalanced
0:4:16: on the product side we have six atoms of
0:4:19: hydrogen so we need three molecules of
0:4:21: hydrogen on the reactant side
0:4:24: and finally the number of atoms on each
0:4:27: side are equal
0:4:30: but an important step is still remaining
0:4:33: in the final form of equation we have to
0:4:36: write the symbols of their physical
0:4:38: states
0:4:39: so a final equation looks like this
0:4:45: you can check out the remaining two
0:4:47: examples in this simulation as well as
0:4:49: practice many other examples on the
0:4:51: edurev app and website which also
0:4:54: provides detailed chapter notes and many
0:4:57: previous year and ncrt questions along
0:5:0: with the solutions to enhance your
0:5:2: learning
0:5:4: let's do a quick recap of this video
0:5:7: firstly revise our concepts of physical
0:5:10: and chemical changes
0:5:12: next we studied about the chemical
0:5:14: reactions
0:5:16: and last but not the least we learned
0:5:19: how to balance the chemical equations
0:5:22: thank you for watching this video and in
0:5:24: the next one we will study the further
0:5:26: topics of this chapter