Participles are forms of verbs that play the role of modifying nouns, other verbs, verbal phrases, among others, just like adjectives and adverbs do. Although sometimes people confuse them with the tenses, participles do not specify exact time of an action, but rather, seem outside of time itself. In English, there are two participles known: the present participle, characterized by the ending - ing- and the past participle, characterized by its two types of endings - ed- for regular verbs, and the ones unique to irregular verbs. While the present participle is known as the progressive, active, or imperfect participle, the past participle is usually referred to as the perfect and passive form. Participles can work as adjectives, adverbs, a short form of a relative clause, adverbial clauses, and also, in mix with other verbs, to form complex verb phrases. Given these explanations, we can then go on ahead and form the sentences as follows:
1. "Well go ice-skating on the frozen lake". This one because frozen is a past participle that uses the verb form "frozen" as an adjective, rather than a simple verb.
2. "You need to read this excellent book". In this case because the request is to use a participle in its infinitive form, but also as an adjective, we need to not just change the modal verb "should", to be able to accomodate the use of "to", but we also need to change the participle "read" to the beginning of the sentence as both "need" and "to read" are describing the book, which is the subject that is being modified.
