physical and chemical properties and changes

The copper sulphide formed is given out as a precipitate.

This insoluble solid is called a precipitate.įor example in a reaction between copper sulphate and hydrogen sulphide, copper sulphide and sulfuric acid are formed. The lime water turns milky when carbon dioxide is passed through it due to the formation of calcium carbonate.Ĭarbon dioxide (CO 2) + Lime water -> Calcium Carbonate (CaCO 3) + Water (H 2 O)įormation of precipitate: In some chemical changes, the product formed separates from the solution and form a different mass of layer.

This can be confirmed by making the gas produced pass through freshly prepared lime water. This is due to the release of carbon dioxide. We will observe gas bubbles coming out of the beaker. Take vinegar (acetic acid) in a glass beaker and add a pinch of baking soda (sodium hydrogen carbonate) to it. Reaction between vinegar and baking soda: The presence of carbon dioxide can be confirmed as it turns lime water milky. Generally the gases produced can be carbon dioxide, hydrogen, ammonia etc. Carbon disulphideĬhange in colour: The colour of the product may differ from that of the reactants.įor example copper sulphate is blue in colour, but after reacting with iron, the product formed ( iron sulphate) is of green colour.Įvolution of gas: Some chemical changes also produce gases. Carbon dioxide + HeatĪ change or reaction in which heat is absorbed from the surrounding is called an endothermic reaction.įor example in a reaction between carbon and sulphur, carbon disulphide is formed with the absorption of heat.Ĭarbon + Sulphur + Heat ……. Some chemical reactions produce heat while some take away heat.Ī change or reaction in which heat is released is called an exothermic reaction.įor example In a reaction between carbon and oxygen, carbon dioxide is formed with the generation of heat.Ĭarbon + Oxygen ……. Some of the properties of a chemical change or chemical reaction are:Ĭhange in energy: Almost all chemical reactions involved energy change. Thus, a chemical change is also called a chemical reaction. For example cooking food, ripening of fruit, lighting a matchstick, aging of leaves and digestion of food etc.Ĭhemical reaction: A chemical change occurs when chemicals react with each other. A chemical change is mostly Irreversible. A physical change is a reversible change.įor example heating of water melting of butter, cutting of paper etc.Ĭhemical changes: A Chemical change occurs when two or more chemical substances react to form new product that have an entirely different set of properties. Physical changes: When a substance undergoes a physical change, it does not give rise to a different kind of substance or there is no new substance is formed. Milk turns sour, seed germinate, the weather changes and fruit ripen.Ĭhanges can be of different types: desirable and undesirable changes, slow and fast changes, temporary and permanent changes, reversible and Irreversible changes and physical and chemical changes.Īll these changes involve one or more substances.

Physical and chemical properties and changes