Physical Change: Overview, Characteristics, & Differences

What happens when you tear a piece of paper into two pieces? You get two smaller pieces of paper! But they are still paper. This type of change is called a physical change. Changes in which no new substances are formed are called physical changes. These changes do not result in the production of new substances.

Some of the common examples of Physical changes are namely, condensation of steam, glowing of an electric bulb, Heating of ice, etc. In this article, we will provide detailed information on the physical change. Scroll down to learn more!

Physical Change: Overview

A physical change is generally observed during melting, freezing, condensing, breaking, crushing, cutting, and bending. Examples of physical changes are powdering of sugar, slicing, shredding, grating fruits and vegetables, and making ornaments out of gold. All of these are physical changes as the original substance remains the same but in a new form.

All reversible changes and some irreversible changes are physical changes. For example, the melting of butter is reversible and a physical change as there is only a state change from solid to liquid form. Breaking glass is irreversible, and a physical change as glass cannot be reconstituted to its original shape. Nevertheless, it remains glass in both forms.

A change in which no new substances are formed can generally be reversed by reversing the conditions called a physical change.

On the other hand, a change in which new substances are formed and which cannot be reversed by reversing the conditions is called a chemical change.

Examples of Physical Change

We have provided some of the common examples of physical changes below:

1. Preparing a solution of salt and sugar
2. Powdering crystals of salt and sugar
3. Powdering chalk stick
4. Magnetisation of iron
5. Changing of water into steam by boiling
6. Condensation of water vapour, such as the formation of clouds, mist, fog, etc.
7. Condensation of steam
8. Glowing of an electric bulb
9. Heating of ice
10. Breaking of a glass tumbler

Changes in the State: You know that solid changes to the liquid and a liquid to the gaseous state on being heated. The opposite change occurs, i.e., a gas changes to the liquid and a liquid to the solid-state, on reversing the conditions, i.e., on being cooled. For example, ice (solid) changes to water (liquid), and water changes to water vapour (gas) on heating, and the changes are reversed by cooling. Obviously, no new substances are formed.

Some solids form vapours directly on being heated. This phenomenon is called sublimation. Ammonium chloride and naphthalene balls are examples of solids that are sublime. On being cooled, the vapours form into solid again. This solid is called the sublimate.

When a solid forms a liquid on being heated, the phenomenon is called melting. And when a liquid forms a solid on being cool, we call the phenomenon freezing.

When a liquid forms a gas on being heated, we say the liquid has vaporized. The opposite of vaporization is condensation. You may have observed drops of water on the inside of the windscreen of a car in winter. This is an example of condensation—the water vapour of the air gets cooled to form drops of water.

Expansion and Contraction

Many materials expand on being heated and contract on being cool without forming any new substances. Such reversible changes take place in

(i) Metallic solids like aluminium, iron, steel, brass, and copper,
(ii) Liquids like water (above \(4\,^\circ {\rm{C}}\)), alcohol and glycerol, and
(iii) Gases like oxygen, nitrogen, carbon dioxide, and air (a mixture of gases).

Below \(4\,^\circ {\rm{C}}\), water behaves in the opposite manner—it expands on being cooled and contracts on being heated. That is why water expands on freezing, i.e., on becoming ice at \(0\,^\circ {\rm{C}}\).

The property of a substance that is contrary to the general rule is said to be anomalous. Hence, this property of water is called the anomalous expansion of water.

Dissolving of a Substance in a Liquid

Salt, sugar, glucose, and many other solid substances dissolve in water. They can be recovered from the solution by evaporating the solvent (water). When one liquid dissolves in another, i.e., when the two liquids form a homogeneous mixture, we say that they are miscible (otherwise, immiscible). Water and alcohol, for example, are miscible liquids. Such liquids can be recovered from their homogenous mixtures by a special method called fractional distillation. Some gases like oxygen, nitrogen, and air also dissolve to some extent in water, from which they can be recovered by heating. Thus, dissolving is a physical change.

Formation of Manure from Leaves

The formation of manure from leaves is a chemical change. Manure is an organic fertiliser used in agriculture. This process is not reversed, and it is a chemical change.

Activities on Physical Change

To understand more about physical changes, let us see some activities.

Activity 1
Aim: To understand a physical change
Materials Required: A balloon
Procedure:
1. Take a balloon and inflate it.
2. Note if there is any change in size and shape.
3. Deflate the balloon.
4. Note if you are able to get back the original size and shape of the balloon.
5. Note if any new substance is formed when you inflate or deflate the balloon.
Observation: The size and shape of the balloon change on inflating and deflating, but no new substance is formed.
Conclusion: Inflating and deflating a balloon are physical changes.

Activity 2
Aim: To find out if stretching spring is a physical change
Materials Required: A spring
Procedure:
1. Take spring and stretch it.
2. Observe a change in its size and shape.
3. Now, release the spring gently.
4. Observe its shape and size again.
Notice of any new substance is formed on stretching or releasing the spring.
Observation: The spring undergoes a change in shape and size. No new substance is formed.
Conclusion: Stretching and releasing a spring are physical changes.

Activity 3
Aim: To observe a physical change with the help of water
Materials Required: Water, a bowl, a burner, and a plate
Procedure: Take some water in a bowl and heat it till you see steam rising. Now, hold a plate over the rising steam. Notice of any new substance is formed.
Observation: Water (liquid) first gets changed into water vapour (gas) and then back into the water (liquid).
Conclusion: There are changes in the state of water, i.e., from liquid to gas and again to liquid. Thus, boiling and condensing of water are physical changes.

Characteristics of Physical Change

Below we have provided some of the characteristics of Physical Change for your reference:

(i) No New Substances are Formed during Physical Change

When ice is heated, it melts and turns into water. When the water is heated further, it turns into steam. The steam condenses and becomes water when it cools. The water forms into ice as it cools further.

Ice, water, and steam molecules, always have two hydrogen atoms and one oxygen atom. As a result, we can conclude that no new substances are formed.

When we add ordinary salt to the water, a salt solution is formed, but no change in the molecules occurs. Water evaporates during evaporation, leaving the salt behind.

(ii) Physical Changes can be Generally Reversed

When a permanent magnet is stroked across a piece of iron, it becomes magnetic. Magnetised iron, on the other hand, loses its magnetic when hammering. When the wax is heated, it turns into a liquid. However, when liquid wax cools, it solidifies.

(iii) There is no Change in Weight during Physical Change

When ten grams of solid wax is melted, it yields \(10\) grams of molten wax.
If you make a salt solution by dissolving \(20\;{\rm{g}}\) of salt in water, you’ll end up with \(20\;{\rm{g}}\) of salt after the water evaporates.

(iv) Only a Little Heat (If Any) is Absorbed or Given off during Physical Change:

If the water absorbs a particular quantity of heat energy to become steam, steam will give off the same amount of heat energy to become water. The heat energy generated during physical changes is never used to alter the composition of the molecules of a substance.

Difference Between Physical and Chemical Change

The difference between physical and chemical change is explained below:

Summary

Many changes are always taking place all around us. There are a few ways in which a substance’s shape, size, or physical state can change. Physical attributes are a substance’s characteristics such as size, shape, colour, and physical state. Physical changes include things like stretching a rubber band and melting butter. There are no new substances generated during a physical change and most physical changes are reversible.

We learnt about physical properties, examples of physical changes, and the differences between physical and chemical changes in this article.

FAQs on Physical Changes

Q.1. What are some of the examples of physical changes?
Ans: Some of the examples of Physical Changes are as follows:
1. Preparing a solution of salt and sugar
2. Powdering chalk stick
3. Powdering crystals of salt and sugar
4. Changing of water into steam by boiling
5. The magnetisation of iron

Q.2. What are 3 examples of a physical change?
Ans: The three examples of physical changes are:
1. Freezing of ice: When water is refrigerated or cooled, it solidifies to form ice.
2. Boiling of water to steam: When water is heated strongly, it starts boiling to form steam. Though the steam and water look different, both are made up of water molecules.
3. Glowing of an electric bulb: When an electric bulb is switched on, the electric current passes through its filament, and it glows to give light. On the other hand, when the current is switched off, the filament returns to its normal condition, and the bulb stops glowing. Hence no new substance is formed during the process.

Q.3. What are some of the characteristics of Physical Change?
Ans: Some of the characteristics of Physical Changes are listed below:
1. No new substances are formed during physical change
2. Physical changes can be generally reversed
3. There is no change in weight during a physical change

Q.4. Are physical changes reversible?
Ans: Yes, physical changes are reversible. A change in which no new substances are formed can generally be reversed by reversing the conditions called a physical change.

Q.5. How is a chemical change different from a physical change?
Ans: During a physical change, the appearance or shape of matter changes, but the type of matter in the material does not. In contrast, a chemical change leads to the production of at least one new substance with new properties.

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