To Change: Mudar v. Trocar

In this post, we will address grammar related to two verbs that people often use interchangeably.  MUDAR & TROCAR

First the similarities.  Both are -AR verbs.  For the most part, both are regular verbs (few non-regular conjugations for TROCAR).  Conjugations here: (MUDAR / TROCAR).

MUDAR is synonymous with: modify, transform, or alter

Examples (from Tatoeba)

1.  O ônibus mudou seu itinerário por causa da obra na avenida Beira Mar
• The bus change its route because of work on Beira Mar street
2. Quando ele viu o professor entrar, mudou rapidamente de assunto
• When he saw the professor enter, he quickly changed the subject 
3. Mudei os meus planos. Mudar de casa agora ficaria muito caro.
• I changed my plans.  Moving right now would be expensive
4. Seria divertido ver como as coisas mudam ao passar dos anos.
• Would be fun to see how things change over the years

TROCAR is synonymous with: switch or substitute

Examples (from Tatoeba)

1. Vamos trocar de lugar
• Lets me change seats with you
2. Você trocou ruim por péssimo
• You've traded bad for worse
3. As criaças trocaram presentes na festa natalina
1. The children exchanged presents at the Christmas party

Research Links

http://www.italki.com/question/58685

http://forum.wordreference.com/showthread.php?t=1887300

http://www.wiziq.com/tutorial/62602-trocar-e-mudar