The conversion of chalk stick into chalk dust is a physical change because both the chalk stick and the chalk dust are just the same substance, only their size is different. So, the condensation of steam (to form water) is a physical change. During the condensation of steam, there is only a change in state from gaseous state to liquid state but no new substance is formed. Actually when hot, rising steam comes in contact with the inverted frying pan, then some of the steam gets cooled and condenses to form drops of liquid water. Now, if we look at the inner surface of the frying pan, we will see drops of water sticking to it. Hold an inverted frying pan by its handle over the rising steam at some distance above the beaker of boiling water. So, the boiling of water (to form steam) is a physical change. No new substance is formed during the boiling of water. Though water and steam look different, they are both made of water molecules. So, during the boiling of water, only a change in state (from liquid to gas) has taken place. Water is a liquid whereas steam is a gas. When the water starts boiling, we can see the steam rising from the surface of hot water. Take some water in a hard glass beaker and heat it by using a burner till it starts boiling. Boiling of Water and Condensation of Steam So, the freezing of water (to form ice) is a physical change. Only a change in state (from liquid to solid) takes place during the freezing of water to form ice, but no new substance is formed. The liquid water changes into solid water called ice. After a few hours, the water kept in the freezer of a refrigerator gets cooled too much, freezes (or solidifies) to form ice. Let us keep the beaker containing water in the freezer compartment of a refrigerator. The change which occurs during the melting of ice to form water can be reversed easily by freezing the water to form ice again. So, the melting of ice (to form water) is a physical change. No new substance is formed during the melting of ice, only a change of state (from solid to liquid) takes place during the melting of ice. Though ice and water look different, they are both made of water molecules. The ice kept in beaker receives heat from the surrounding air to melt and form water. We will see that ice melts to form water. Take some ice in a beaker and keep it aside for some time. Stretching metals to form wires Melting of Ice and Freezing of Water Glowing of an electric bulb (or tube-light) Making soda water by dissolving carbon dioxide (4) A temporary change in colour may take place in a physical change.Ĭondensation of steam (to form water Evaporation of water to form water vapour)Ĭondensation of water vapour (to form liquid water)Ĭonversion of chalk stick into chalk dustĬutting of a log of wood (into pieces of wood)ĭissolving salt in water (to make salt solution)ĭissolving sugar in water (to make sugar solution) (3) Very little energy is either absorbed or evolved in a physical change. A physical change can be easily reversed. (2) A physical change is a temporary change. (1) No new substance is formed in a physical change. The important characteristics of a physical change are as follows: Those changes in which a substance undergoes a change in its physical properties are called physical changes. The changes in state, size, shape and colour of a substance are physical changes. The properties such as state, size, shape and colour of a substance are called its physical properties. Those changes in which no new substances are formed, are called physical changes. 3 Boiling of Water and Condensation of Steam.Thus, heat is the cause of the change of state of ice from solid to liquid. Ice must be given some heat to melt and change into water. Ice does not melt on its own to form water. There is always a cause which brings about a change in a substance. The change in a substance does not occur on its own. Some of the changes observed by us in our everyday life are: So, the melting of ice involves a change in state from solid state to liquid state. Ice is a solid whereas water is a liquid. Melting of ice is a common change around us. When one or more properties of a substance become different, we say that a change has taken place in it. Question 5 Explain why boiling of water is said to be physical change?Īll substances have certain properties such as state (solid, liquid or gas), size, shape, colour, smell, temperature, composition and structure, etc. Question 4 What are the characteristics of physical changes?

Question 3 Explain why melting of ice to form water is said to be physical change?

Question 2 Give few examples of physical changes from everyday life?

Some examples of physical changes