Sate which of the following pertains to- chemical changes. a] substance retains its identity b] The change is permanent c] No new substance is formed. d] is easily reversible e] Produces one or more new substance in its composition. f] The change is temporary g] The composition and properties of the original substance are not altered.
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Q3
Give two examples for each of the following cases: [3 marks]
(a) Physical changes that are reversible
(b) Physical changes that are not reversible
(c) Chemical changes
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Q4
Matter undergoes a change. The changes are of two types: Physical and chemical change.
A physical change is a change that involves only a change in the physical state of matter. Its chemical properties remain the same. Usually increasing the temperature or applying pressure or both bring about a physical change. On reversing the condition, that is reducing the temperature or reducing the pressure or both, the original state of matter is restored. In other words, physical changes are reversible.
A chemical change is a change that involves a change in the chemical composition of matter. A new substance is formed. In a chemical change, new chemical and physical properties of the substance are formed. In a chemical change, the chemical and physical properties of the substance formed will be different from the original substance.
In a chemical change, the properties that change are :
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Q5
Consider the following statements:
(i) Chemical changes are irreversible.
(ii) Chemical changes produce new substances.
(iii) Chemical changes does not involve large energy changes.