Question

1. 2Distnguish between a physical change and a chemical change

2.Differentiate between a mixture and a compound​

Answer 1

Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds.[1]

Physical changes occur when objects or substances undergo a change that does not change their chemical composition. This contrasts with the concept of chemical change in which the composition of a substance changes or one or more substances combine or break up to form new substances. In general a physical change is reversible using physical means. For example, salt dissolved in water can be recovered by allowing the water to evaporate.

A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density.

An example of a physical change is the process of tempering steel to form a knife blade. A steel blank is repeatedly heated and hammered which changes the hardness of the steel, its flexibility and its ability to maintain a sharp edge.

Many physical changes also involve the rearrangement of atoms most noticeably in the formation of crystals. Many chemical changes are irreversible, and many physical changes are reversible, but reversibility is not a certain criterion for classification. Although chemical changes may be recognized by an indication such as odor, color change, or production of a gas, every one of these indicators can result from physical change.

Answer 2

1. Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.
2. Compound are substances which can be formed by chemically combining two or more elements. Mixtures are substances that are formed by physically mixing two or more substances. Compounds can be of three types, which are: covalent compounds, metallic compounds and ionic compounds.