Everything around us is changing. Nothing is permanent. The universe is never the same again. Let us take some simple examples of changes that we see in our daily life. In this blog, we will discuss what is a physical change. We dissolve sugar in water and add ice to it to make cold drinks.

Making a cold drink is a change. When we blow up a balloon, stretch a rubber band, make a paper airplane, in all these cases, changes are occurring. Souring of milk and setting curd from milk are also examples of changes.

There are some changes in which no new substance is formed, only the physical properties of the substance such as physical state, color, hardness, rigidity, fluidity, density, melting point, boiling point, etc. change. Such changes are referred to as Physical Changes. These are temporary changes and can be reversed.

Examples of Physical Changes:

● Melting of ice to form water where there is an only physical change in the state of water from solid to liquid,
● Freezing of water to form ice
● Condensation of steam to form water
● Preparing salt solution and then recovering back salt by evaporation.
● Breaking off coal
● Mixing iron filings and sulfur are some good examples of physical changes.

In order to understand physical changes, let us perform some activities:

Activity1: Take a paper sheet and cut it into four pieces. Is there any change in the property of the paper? No, as Paper is still a paper. Is any new substance formed?? No

Activity 2: Take a small amount of modeling clay. Model the clay into the shape of a ball. Now remodel the ball into the shape of a cylinder and then the cylinder into a cube.

Activity 3: Take some ice cubes in a glass. Place the glass in the sun. Let some ice melt. Now place the glass containing a mixture of ice and water in the freezer. You find that liquid water becomes solid ice again.

Activity 4: Boil some water in a container. Hold an inverted pan by its Bakelite/ wooden handle over the steam at some distance from the container. What do you observe? Tiny droplets of water appear on the inner surface of the pan.

Activity 5: Hold the head of the long nail with a pair of tongs. Keep the pointed end of the nail in the flame of a gas burner for a few minutes. What do you observe? Does the color of the nail change? The color of the tip of the nail becomes red. Now remove the nail from the flame.

Now if you have carefully observed the above activities: You will find that in activities 1 and 2 we saw that the paper sheet and modeling clay underwent changes in shapes. In activity 3 water changed its states from solid to liquid and then from liquid to solid.

In activity 4 water changed its state from liquid to gas and then gas to liquid. In activity 5, the colors of the nail changed from grey to red and then red to grey again.

What is common in all these changes? Yes, the substance undergoing the change is able to regain its original state. Properties such as size, shape, color, and state of matter of a substance are called its physical properties.

A change in the shape, size, color, or state of matter of a substance is called a physical change. In such a change no new substance is produced. A very important point regarding physical change is that a physical change is generally reversible.

Hence activity 1, 2,3,4,5 all demonstrate physical changes in the substance undergoing change, as no new substance is formed and the change is reversible. Whether it is cutting of paper, modeling clay, melting of ice, boiling water, or heating iron nail.

Some more examples of physical changes are:

Melting of butter on warm toast.
Formation of waves in oceans.
Formation of bubbles in water or soap solution.
Glowing of an electric bulb.
Magnetizing an iron piece.
Evaporation of water from the open surface of the water bodies.
Crushing a can
Making locks, keys, chains, nuts, and bolts from iron.

In all the above examples, no new substance is formed and the change is reversible i.e. the substance undergoing change can be reversed back to its original form.

CRYSTALLISATION

In earlier classes, you have learned that salt can be obtained by the evaporation of seawater. The salt obtained in this manner is not pure and its crystals are small. The shape of the crystals cannot be seen clearly. However, large crystals of pure substances can be formed from their solutions.

The process is called crystallization. It is an example of a physical change. Let us see another process of crystallization. Let us take of water in a beaker and add a few drops of dilute sulphuric acid.

Now add copper sulfate powder slowly while stirring continuously. Now heat the solution. Now, after filtering and cooling the solution, you can see the crystals of copper sulfate. This entire process is the crystallization of copper sulfate salt.

Read More- What is Chemical Change: Definition and Example of Chemical Change