Classify the following as physical or chemical properties (a) The composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements. (b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas. (c) Metallic sodium is soft enough to be cut with a knife. (d) Most metal oxides form alkalis on interacting with water.

Answer:

Most of the substances that we see around have certain characteristics and properties by which they can be classified or identified. As such, substances are usually classified based on their chemical and physical properties.

Physical property

  • Physical properties are properties that can be observed without bringing a chemical change.
  • No chemical reaction is needed here.
  • It is mostly used in identifying or describing the substance.

Chemical property

  • Chemical properties are properties that can be observed or measured when a substance undergoes a chemical change.
  • A chemical reaction needs to be conducted to show the property.
  • It can be used to predict how substances react.

Physical property

Chemical property

(a) The composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements.

(b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.

(c) Metallic sodium is soft enough to be cut with a knife.

(d) Most metal oxides form alkalis when interacting with water.

(a) Composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements. It is a chemical property because no new compound is formed as the steel is an alloy and alloy and is a homogeneous mixture of two or more metals or of metallic elements with non-metallic elements.

(b) It is a chemical property because zinc reacts with HCL to give out zinc chloride and hydrogen gas.

(c) The cutting knife will not involve any chemicals reaction and did not form a new compound hence it is a physical property.

(d) It is chemical property as the new compound is formed by the interaction of metal oxides with alkalis.

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