A change in the physical properties of a substance is called physical change. It is a temporary change.
For example melting of ice.
A change in chemical properties of a substance is called chemical change. It is permanent change.
For example, rusting of iron.
The property which is associated with the physical state of matter is called physical property. For example, colour, smell etc.
The property which is associated with the chemical composition of matter. For example, reactivity etc.
The temperature at which a solid starts melting and co-exist in dynamic equilibrium with liquid state is called melting point.
The temperature at which a liquid starts freezing and co-exists in dynamic equilibrium with solid state is called freezing point.
Boiling point is the specific temperature for a liquid at which, it begins to boil and converts from liquid state to gaseous state.
The number of grams of solute dissolved in 100 grams of solvent at a particular temperature is called solubility.
It is a chemical change in which oxygen in the moist air reacts with the iron to convert it into iron oxide (rust).
Tarnishing is a thin film of corrosion that forms on the surface of the objects made of silver, copper, brass, aluminium, magnesium etc.
1. Physical change: It involves a change in the physical properties of a sub stance. The chemical composition of the substance does not change. It is easily reversible. 2. Chemical change: It involves a change in the chemical properties of a substance. The chemical composition of the substances change and new substances with different properties are formed. It is not easily reversible
Oxygen plays an important role in various chemical reactions, especially those involved in combustion and respiration. Oxygen reacts in these reactions to release energy and support in life processes.
It is a chemical change in which oxygen in the moist air reacts with the iron to convert it into iron oxide (rust).
To prevent rust:
Keep Dry: Keep metal objects dry.
Paint: Apply paint to protect metal from moisture.
Oil: Use oil or grease to create a barrier against water.
Galvanization: Coat metal with a layer of zinc to prevent rust.
Use Rust-resistant Materials: Choose materials that are less likely to rust, like stainless steel.
Combustion includes burning of fossil fuels. The gaseous emission during burning of fossil fuels is the primary source of environmental pollution.
Combustion:
• Increases greenhouse effect which causes global warming.
• Incomplete combustion produces carbon monoxide gas which is poisonous.
• Combustion causes smog and acid rain.
