whch is Chemical Change
Combustion, reacts with acid, water and air
Cut apple, heat changes, alcohol evaporates, ice melts
Tarnishes, rust, ph, rots, food digest
Melting point, hardness, luster, odor
Chemical Change is represented by the following examples:
1. Combustion: When a substance reacts with oxygen to produce heat and light, such as burning wood or gasoline.
2. Reacts with acid: When a substance undergoes a chemical reaction when exposed to an acid, such as the fizzing of baking soda when mixed with vinegar.
3. Reacts with water: When a substance undergoes a chemical change when exposed to water, such as the rusting of iron when in contact with moisture.
4. Reacts with air: When a substance undergoes a chemical change when exposed to air, such as the oxidation of metal, resulting in the formation of rust.
5. Tarnishes: When a metal loses its shine and develops a dull surface due to oxidation, such as the tarnishing of silver jewelry over time.
6. Rust: When iron or steel reacts with oxygen in the presence of moisture, resulting in the formation of iron oxide, which is commonly known as rust.
7. pH: When a substance undergoes a chemical change in its acidity or alkalinity, such as the digestion of food in the stomach with the help of stomach acid.
8. Rots: When organic matter decomposes due to the action of bacteria, fungi, and other microorganisms, resulting in a breakdown of the material and the release of gases.
9. Food digest: The process by which food undergoes chemical changes in the body to be broken down into nutrients and absorbed for energy.
10. Odor: When a substance emits a distinct smell due to the release of volatile compounds, such as the smelling of rotten eggs due to the presence of hydrogen sulfide gas.
On the other hand, the properties mentioned in the last set (melting point, hardness, luster, odor) are physical properties rather than chemical changes.
Chemical changes refer to the process of substances undergoing a chemical reaction, resulting in the formation of new substances with different chemical properties. In contrast, physical changes involve only a change in state or appearance of a substance without altering its chemical composition.
Let's categorize the given examples into chemical changes and physical changes:
Chemical Changes:
1. Combustion: If a substance reacts with oxygen, producing heat, light, and often a flame, it is considered a chemical change. For example, burning wood or a candle releases energy and transforms the substances into carbon dioxide and water vapor.
2. Reacts with acid: When a substance reacts with an acid, a chemical reaction takes place. It may result in the formation of new substances. For instance, when calcium carbonate reacts with hydrochloric acid, it produces carbon dioxide gas, water, and calcium chloride.
3. Water and air reactions: Certain substances undergo chemical changes when they react with water or atmospheric oxygen. These reactions can lead to the formation of new compounds. For example, when iron reacts with oxygen in the presence of moisture, it forms iron oxide, which is commonly known as rust.
Physical Changes:
1. Cut apple: Cutting an apple or any other fruit represents a physical change because it alters the shape or size of the object without modifying its chemical composition.
2. Heat changes: Heating a substance generally causes a physical change. It can change the state of the substance from solid to liquid or liquid to gas. For example, melting ice is a physical change as it transforms from a solid to a liquid state.
3. Alcohol evaporates: Evaporation is a physical change where a liquid substance changes its state into a gas without any chemical reactions. Alcohol evaporating is an example of this.
4. Ice melts: This is also a physical change as it involves the conversion of a solid substance (ice) into a liquid (water) without any chemical reaction.
5. Tarnishes, rust, ph, rots, food digest: These are examples of chemical changes. Tarnishing of metal, rusting of iron, changes in pH indicating chemical reactions, the process of food rotting, and digestion all involve chemical reactions that result in the formation of new substances.
6. Melting point, hardness, luster, odor: These characteristics, such as melting point, hardness, luster, and odor, generally describe the physical properties of substances, indicating their physical state or appearance, rather than undergoing chemical changes.
Understanding the distinction between chemical and physical changes is important as it helps us comprehend various natural phenomena and processes happening around us.
Chemical changes refer to the processes where one or more substances are converted into new substances with different properties. Based on the given options, the chemical changes are as follows:
1. Combustion: Combustion is a chemical change that occurs when a substance reacts with oxygen and produces heat and light. It is commonly observed in burning processes such as when wood or gasoline is burned.
2. Reacts with acid: When a substance reacts with an acid, a chemical change takes place. This reaction can result in the formation of new substances and may produce gas, heat, or other observable changes.
3. Tarnishes: Tarnishing is a chemical change that occurs when a metal reacts with substances in the air, such as oxygen, sulfur, or water vapor. This reaction can cause the metal to lose its shine and form a dark-colored layer on its surface.
4. Rust: Rust is a specific type of tarnishing that occurs when iron or steel reacts with oxygen and moisture in the air. This chemical change results in the formation of hydrated iron(III) oxide, commonly known as rust.
5. pH: Changes in pH indicate chemical changes. pH refers to the measure of acidity or alkalinity of a substance. When substances undergo a chemical reaction that changes their pH, it implies a chemical change has occurred.
6. Rots: When organic matter, such as food or plants, decomposes due to the action of microorganisms like bacteria and fungi, a chemical change called rotting occurs. Rotting involves the breakdown of complex organic molecules into simpler substances.
It's important to note that the remaining options mentioned - melting point, hardness, luster, and odor - are not examples of chemical changes. They refer to physical properties or characteristics of substances and do not involve the formation of new substances.