Matter, Everywhere and Everywhen: present perfect y simple past, conectores de secuencia y causa (Inglés 3)
Actualizado el 8 min de lectura 43 ejercicios resueltos
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En Matter, Everywhere and Everywhen investigas las propiedades de sustancias de uso diario (sal, azúcar, vinagre, café…) y, con un medidor de conductividad hecho en casa, descubres qué tipo de enlace tienen. En inglés aprendes a distinguir el present perfect del simple past y a usar conectores para dar instrucciones en orden y explicar causas y consecuencias.
En tu libro: este proyecto está en las páginas 36 a 49 de Projects and Readings. Third Grade (SEP). La gramática está en las páginas 38 a 40 y el vocabulario en la 41.
De qué trata el proyecto
La lectura de la página 37 cuenta la historia de unos campistas en una playa: con una ola de calor, uno de ellos se deshidrata. Recuerdan que las bebidas con electrolitos son dulces y le dan agua con azúcar, pero la persona no mejora y tienen que llevarla al hospital. El problema es que el azúcar no es un electrolito: los electrolitos son sustancias que, disueltas en agua, conducen la electricidad, como la sal (cloruro de sodio, un compuesto con enlace iónico). El azúcar tiene enlaces covalentes y no conduce.
Por eso el proyecto propone construir un medidor de conductividad con un cable, un led y una pila (páginas 44 y 45) y probar qué sustancias se disuelven en agua y cuáles encienden el led.
Vocabulario del proyecto
| English | Español | Ejemplo |
|---|---|---|
| substance | sustancia | Salt and sugar are everyday substances. |
| dehydration | deshidratación | One camper showed symptoms of dehydration. |
| electrolyte | electrolito | Salt is an electrolyte. |
| bond | enlace | Table salt has an ionic bond. |
| soluble | soluble | Sugar is soluble in water. |
| to conduct electricity | conducir la electricidad | Salt water conducts electricity. |
| hypothesis | hipótesis | We tested our hypothesis in the lab. |
| melting point | punto de fusión | Ionic compounds have a high melting point. |
Gramática: present perfect y simple past
| Present perfect | Simple past | |
|---|---|---|
| Afirmativa | I have studied all the lessons. | I completed my homework yesterday. |
| Negativa | She has not taken chemistry this period. | She did not take chemistry last semester. |
| Pregunta | Have you ever performed an experiment? | Did you perform an experiment last period? |
| Expresiones de tiempo | today, this year, ever, never, in the last six months | yesterday, two weeks ago, last year, in 2020 |
La regla: usa el simple past cuando la acción empezó y terminó en un tiempo pasado (casi siempre dices cuándo). Usa el present perfect cuando la acción sigue relacionada con el presente: continúa hoy, tiene efectos ahora o pasó en un periodo que no ha terminado (this year, today).
- I have done three experiments this month.
- I did three experiments last month.
El error más común es mezclarlos con una fecha: I have finished it yesterday → I finished it yesterday.
Ejercicios del libro resueltos
Página 39: present perfect
Ejercicio 2: escribe el verbo en present perfect
a) The scientists (present) evidence that global warming is increasing every year.
b) In the past few years, wildfires (increase) in scale and frequency in many communities.
c) Researchers (debate) the value of teaching students to interpret phenomena in terms of energy forms.
d) Recent studies (show) that a few students develop an understanding of energy concepts.
e) In my town, the river (decrease) its level.
Ver respuestas
a) The scientists have presented (present) evidence that global warming is increasing every year.
b) In the past few years, wildfires have increased (increase) in scale and frequency in many communities.
c) Researchers have debated (debate) the value of teaching students to interpret phenomena in terms of energy forms.
d) Recent studies have shown (show) that a few students develop an understanding of energy concepts.
e) In my town, the river has decreased (decrease) its level.
Ejercicio 3: elige la opción correcta
Ver respuestas
Have you mixed the ingredients?
Después de have va el participio: mixed.
She didn’t complete the experiment.
Complete está en forma base, así que antes va un auxiliar; la opción que forma una oración natural es la negativa didn’t.
I took physics classes.
Taken necesitaría have, y taked no existe: el pasado de take es took.
We discovered the formula to make it rain.
Has she done the experiment?
She lleva has, y done es participio (con did sería Did she do…?).
Página 40: present perfect o simple past
Ejercicio 4: escribe la forma correcta del verbo
a) I (learn) in this project that electrolytes (save) people’s lives.
b) I (not/do) any experiment last school year, but I (do) a few during this one.
c) Scientists (just/make) many discoveries on behalf of human beings.
d) Scientists (just/tell) us how to solve the climate change crisis but people (not/listen) carefully.
e) My science magazine (arrive) almost every week since I first (subscribe).
f) With the help of technology, doctors and nurses (make) significant steps in treating and preventing diseases.
g) The effects of technology on society (be) both positive and negative.
Ver respuestas
a) I learned (learn) in this project that electrolytes have saved (save) people’s lives.
b) I didn’t do (not/do) any experiment last school year, but I have done (do) a few during this one.
c) Scientists have just made (just/make) many discoveries on behalf of human beings.
d) Scientists have just told (just/tell) us how to solve the climate change crisis but people didn’t listen (not/listen) carefully.
e) My science magazine has arrived (arrive) almost every week since I first subscribed (subscribe).
f) With the help of technology, doctors and nurses have made (make) significant steps in treating and preventing diseases.
g) The effects of technology on society have been (be) both positive and negative.
En b) y e) se ve la regla completa: last school year (terminado) va en simple past, during this one (sigue en curso) en present perfect; con since, la acción que continúa va en present perfect y el momento de inicio, en simple past (since I first subscribed).
Página 40: el orden del experimento (Reading)
Escribe el número de cada paso (1 a 8)
Pour the upper liquid into another container until it separates from the lower liquid.
Subsequently, pour the lower liquid into another container to separate it from the sand or earth sediments.
Place a container for liquids, preferably transparent, of 500 ml.
Add the liquids to the transparent container.
Add a tablespoon of sand or soil.
Mix the materials perfectly well.
Measure 250 ml of water and 100 ml of edible oil.
Wait until the elements are separated.
Ver respuestas
7 Pour the upper liquid into another container until it separates from the lower liquid.
8 Subsequently, pour the lower liquid into another container to separate it from the sand or earth sediments.
1 Place a container for liquids, preferably transparent, of 500 ml.
3 Add the liquids to the transparent container.
4 Add a tablespoon of sand or soil.
5 Mix the materials perfectly well.
2 Measure 250 ml of water and 100 ml of edible oil.
6 Wait until the elements are separated.
Vocabulario: conectores de secuencia y de causa
Para dar los pasos de un experimento se usan conectores de secuencia: first, second, then, next, after that, furthermore, finally, at the end. Para explicar causas y consecuencias: because (of), so, therefore, as a result, consequently, for this reason, cause.
- Because of the rainy weather, we cancelled the presentation.
- The Moon’s gravitational pull causes the ocean’s tides.
Página 41: los pasos del experimento de densidad
Ejercicio 1: escribe un conector de secuencia
a) , place two glasses of the same size, with approximately 250 ml of water each.
b) , fill ¾ of the glasses.
c) , label them as glass A and glass B.
d) , add two tablespoons of salt to glass A.
e) , perfectly dissolve the salt.
f) , immerse an egg into each glass.
Ver respuestas
a) First, place two glasses of the same size, with approximately 250 ml of water each.
b) Second, fill ¾ of the glasses.
c) Then, label them as glass A and glass B.
d) After that, add two tablespoons of salt to glass A.
e) Next, perfectly dissolve the salt.
f) Finally, immerse an egg into each glass.
En el ejercicio 2 de la página 41, el huevo flota en el vaso A y se hunde en el B: el agua con sal tiene mayor densidad que el huevo, y el agua sola, menor.
Ejercicio 3: escribe el conector de causa o consecuencia
a) If you mix salt, water, juice, and honey, is homemade electrolyte water.
b) Plants grow of the Sun’s heat and light.
c) When water is heated, the molecules move quickly, the water boils.
d) of studying hard, you aced your test!
e) Tsunamis happen tectonic plates shift.
Ver respuestas
a) If you mix salt, water, juice, and honey, the result is homemade electrolyte water.
b) Plants grow because of the Sun’s heat and light.
c) When water is heated, the molecules move quickly, therefore the water boils.
d) As a result of studying hard, you aced your test!
e) Tsunamis happen because tectonic plates shift.
Practica más
¿Present perfect o simple past?
Ver respuestas
Marie Curie won the Nobel Prize twice.
Marie Curie murió en 1934: es un hecho terminado.
Have / done you ever
We sent the lab report two days ago.
This year, our class has done five experiments.
This year no ha terminado.
Comprueba lo aprendido
1. ¿Cuándo se usa el simple past en lugar del present perfect?
Cuando la acción terminó en un momento pasado, casi siempre con una expresión de tiempo terminado: yesterday, last year, two weeks ago, in 2020.
2. Corrige: «I have visited the lab yesterday».
I visited the lab yesterday. Con yesterday se usa simple past.
3. ¿Por qué el agua con azúcar no sirvió como bebida de electrolitos?
Porque el azúcar no es un electrolito: tiene enlaces covalentes y al disolverse no forma iones. Los electrolitos, como la sal, forman iones en el agua y conducen la electricidad.
Temas relacionados: enlace iónico y covalente en Saberes y pensamiento científico 3.
Referencias
- Secretaría de Educación Pública (2025). Uérakua anapu uantakua. Projects and Readings. Third Grade. Secondary. SEP, pp. 36-49.
- Murphy, R. (2019). English Grammar in Use (5.ª ed.). Cambridge University Press, unidades 13 y 14.
