What are physical and chemical features?

The physical property of a compound could be determined without modifying the originality of the compound. Examples of physical properties are density, hardness, color, boiling, and melting point. The chemical property expresses the ability of a compound to undergo a particular chemical change.

Physical properties

Physical property is a property, which is measurable and its value expresses the state of the physical system. Physical properties are also called observables. The change of physical properties of the system could be used to express its changes between the momentary states.

Classification of physical properties

The physical properties could be categorized as extensive and intensive properties. The intensive property will not depend on the size of the system, nor on the quantity of matter in the system whereas an extensive property gives an additive relationship. Intensive properties include temperature, state of matter, and density. Extensive properties include mass, volume, and size.

Physical change

A physical change includes the change of physical properties. Examples of physical changes include transition to a gas, melting, textural change, change of strength, size, color, density, and volume, etc. If a compound undergoes a physical change, its composition remains the same but its molecules are rearranged. The physical change affects the physical properties. A physical change will not involve the formation of energy. Some physical changes are described below.

Heating and Cooling

Some substances change from liquids to gases & from solids to liquids when heated and the process is reversed when cooled. In the case of sublimation, the substances change directly from solid to gas. Example: sublimation of iodine & carbon dioxide.

Crystallization

Most of the elements and compounds produce crystals. For example, carbon could produce various forms including graphene, fullerenes, graphite, and diamond.

The crystals which are present in the metals have a major effect on the physical properties of the metal such as strength and ductility. The modification of size, shape, and crystal type can be done by physical rolling, hammering, and heat.

Magnetism

The ferromagnetic materials could be changed into magnetic. This change is reversible and will not affect the chemical composition.

Alloying

The mixing of various metal elements is called alloying. For example, brass is an alloy, which is formed by the mixing of zinc and copper. It is a physical change, which could not easily be undone through physical means. In the case of alloys, mercury (Hg) is one of the metals that could be extracted physically through melting the alloy & boiling the Hg off as vapor.

Mixtures

Mixtures of the compounds which are not soluble are easily separated by settlement or physical sieving. Mixtures could have various properties from the individual elements. The mixture of water with fine sand will form sandcastles.

Texture

The texture of the substance could be varying with the physical change. When a piece of wood was waxed, sanded, or polished, it could have a different texture than its initial texture.

These physical changes can cause changes in physical properties such as shape, color, luster, density, malleability, and viscosity, etc.

Chemical properties

The properties of matter, which could be noticed and analyzed by carrying out a chemical reaction or by a chemical change are known as chemical properties. Chemical properties could be more evident when there is an alteration in the structure of the sample/substance. The heat of combustion, enthalpy of formation, toxicity, oxidation states, formation of chemical bonds, reactivity are examples of this type of properties.

Examples of chemical properties

Certain examples of chemical properties include,

Flammability: The measure of how easily a sample would ignite or how long it can go through a combustion reaction is flammability. One will not know how easily a substance would burn unless it is ignited, therefore flammability is a chemical property.

Chemical stability: Chemical stability otherwise called thermodynamic stability is also a chemical property. Chemical stability is obtained by certain conditions, and it cannot be seen without unrevealing the sample to that particular situation. So, chemical stability is a chemical property.

Oxidation state: Every element has its oxidation number or oxidation state. The measure of electron loss is oxidation. Integers are used to represent the oxidation state. The oxidation state is unknown until and unless an element takes part in a chemical reaction to form chemical bonds, so the oxidation state is a chemical property.

Chemical change

A chemical change is used to recognize a chemical property. One or more kinds of matter, which is different from the matter found prior to the change, are produced by a chemical change. In simple words, one substance gets converted to another substance by a chemical change or chemical reaction. Some of the examples of chemical changes are,

• Formation of water from hydrogen and oxygen is a chemical reaction as the constituents of the substance are different during the initial process and at the end of the process.
• Explosion of nitroglycerin is a chemical reaction because the original substances produce different kinds of gases.
• Chemical reactions, which are done in the lab, are chemical changes.
• All combustion reactions come under chemical changes.

Why is it significant to know about the chemical properties of a substance?

Using the chemical properties of a substance, one can get the following information:

• Chemical property is used for the classifying the sample.
• Chemical property is used to identify an unknown substance.
• Using chemical properties, the substance can be purified.
• Chemical properties are used to predict the behavior and uses of a substance.
• With the help of chemical properties, one substance can be isolated from another.

Difference between physical properties and chemical properties

Context and Applications

This topic is important for,

• High school (Grade 11 and Grade 12 students)
• Bachelors in Chemistry
• Bachelors in Biochemistry

Practice Problems

Question 1: Radioactivity is an example of ____ property.

1. Physical property
2. Chemical property
3. Chemical change
4. Physical change

Answer: Option 2 is correct.

Explanation: Radioactivity is a chemical property. The emission of radiation from an atom, which contains an unstable nucleus, is radioactivity or radioactive decay. During the radioactive decay process, a nuclear reaction occurs (one element changes to another element).

Question 2: The statement that is not true about physical change is ____.

1. No energy is lost or gained
2. Irreversible
3. Formation of no new substance
4. None of the above

Answer: Option 3 is correct.

Explanation: In a physical change, only the physical properties of the matter are changed, and no new substance is formed.

Question 3: An example of chemical change is ____.

1. Heating of sugar
2. Sugar is a white solid
3. Sugar has a sweet taste
4. None of the above

Answer: Option 1 is correct.

Explanation: Heating sugar is a chemical change because the small groups are obtained when sugar molecules are broken and when they are further broken down, carbon molecule is obtained and gases are released.

Question 4: Solubility is an example of ____.

1. Physical property
2. Chemical property
3. Both 1 and 2
4. None of the above

Answer: Option 1 is correct.

Explanation: An example of physical property is solubility. This is because when a substance is dissolved there is no change in the chemical structure of the substance. Solubility is determined by observation.

Question 5: Cooking rice is a physical change. Is the given statement correct?

1. The statement is correct
2. The statement is incorrect
3. Neither 1 nor 2
4. None of the above

Answer: Option 2 is correct.

Explanation: Cooking rice is not a physical change. While cooking rice or any food, the chemical composition is changed so, the cooking of rice or any food is a chemical change. The statement is incorrect.