physical change and chemical change are made
Physical changes and chemical changes are distinguished by the type of transformation that occurs in a substance.
Physical changes are changes that do not alter the chemical composition of a substance. They only affect its physical properties such as shape, size, density, state (solid, liquid, gas), and phase transitions (melting, freezing, boiling, condensation). Examples of physical changes include melting ice, boiling water, dissolving sugar in water, breaking a glass, or cutting a piece of paper.
Chemical changes, on the other hand, involve a rearrangement of atoms or molecules in a substance, resulting in the formation of new substances with different chemical properties. Chemical changes are also known as chemical reactions. Examples of chemical changes include burning wood, rusting iron, baking a cake, digesting food, or fermentation in the production of alcohol.
In summary, physical changes only affect the physical properties of a substance, while chemical changes involve a transformation of the substance at the molecular level, resulting in the formation of new substances.
Physical changes and chemical changes are two different types of processes that occur in matter.
Physical changes involve a rearrangement of molecules or particles within a substance, but do not result in the formation of new substances. The original substance remains the same chemically, only its physical properties may change. Examples of physical changes include changes of state, such as melting, freezing, boiling, or condensation. For instance, when ice melts to form water, no new substances are formed, only the physical state of the substance changes.
Chemical changes, on the other hand, involve a transformation of one or more substances into new substances with different chemical properties. This occurs when the chemical bonds between atoms are broken and new bonds are formed. Chemical changes often involve a change in color, the formation of gas or precipitate, or the release or absorption of energy. Examples of chemical changes include combustion (burning), rusting of iron, digestion of food, and the decomposition of organic matter.
In summary:
- Physical change: Only the physical properties of the substance change, while the chemical composition remains the same.
- Chemical change: The chemical composition of the substance changes, resulting in the formation of new substances with different properties.
To understand the difference between physical and chemical changes, let's start by defining each term:
1. Physical Change: A physical change refers to a change in the physical properties of a substance without altering its chemical composition. It does not involve the formation of new substances.
2. Chemical Change: A chemical change, also known as a chemical reaction, refers to a process in which one or more substances are converted into different substances with distinct properties. This change involves the breaking and forming of chemical bonds.
Now, let's explore how physical and chemical changes are made:
1. Physical Change:
- Physical changes can be made by altering the physical conditions or properties of a substance. This can be achieved through various means, including:
- Change in temperature: Heating or cooling a substance can cause it to expand or contract, resulting in a change in its physical state (e.g., from solid to liquid).
- Change in pressure: Applying pressure to a substance can cause it to compress or expand, altering its physical volume or density.
- Change in state: Changing the state of matter by adding or removing energy can result in physical changes. For example, freezing water changes its state from liquid to solid, while boiling water changes it from liquid to gas.
- Mechanical force: Applying force or pressure, such as bending, stretching, or breaking an object, can induce physical changes.
- Mixing or separating substances: Combining or separating different substances without altering their chemical properties is a physical change. For instance, dissolving sugar in water is a physical change as the substances can be easily separated.
2. Chemical Change:
- Chemical changes are made through chemical reactions, which involve the rearrangement of atoms and the formation of new chemical bonds. Some ways that chemical changes occur include:
- Combination: When two or more substances react to form a new compound, a chemical change is taking place. An example is the reaction between hydrogen and oxygen to form water.
- Decomposition: When a compound breaks down into simpler substances, a chemical change occurs. An example is the decomposition of hydrogen peroxide into water and oxygen gas.
- Oxidation and reduction: Chemical reactions involving the transfer of electrons between species, known as redox reactions, are also examples of chemical changes. Rusting of iron is an instance of oxidation, where iron reacts with oxygen in the presence of water, causing it to corrode.
In summary, physical changes involve altering the physical properties of a substance without changing its chemical composition, while chemical changes involve the formation of new substances through chemical reactions. These changes can be made by manipulating various factors such as temperature, pressure, mixing, or introducing different substances.