Inventions

Unit 8: Past Continuous vs. Simple Past

Louis Pasteur

Accidental Inventions

Peter: What did you do today?
John: I surfed the internet. I looked for scientific inventions.
Peter: That sounds good. What did you learn?
John: I learned that many of the inventions we see today were simply accidents?
Peter: What do you mean?
John: I mean... many scientists were working when they accidentally discovered something.
Peter: Really? Do you have an example?
John: Yes. A doctor was working on a new headache medicine when he discovered Coca Cola!
Peter: I didn't know that!
John: Here is another one: The microwave oven... Percy Spencer. He was working with radar when the microwave energy melted the chocolate bar in his pocket.
John: And Constantin Fahlberg. He was a chemist. He was working in his lab when a substance spilled onto his hand. He tasted it and found it to taste sweet! So saccharin, the first artificial sweetener was born in 1879.

Comprehension (T / F)

1. There are four inventions in the dialogue.
2. The doctor had a headache when he discovered Coca Cola.
3. Percy Spencer wanted to invent the microwave oven.
4. Constantin Fahlberg discovered saccharin by chance.

Understanding the Tenses

The Golden Rule

We often use the Past Continuous and the Simple Past together to show that a short action happened in the middle of a longer action.

Tense Function Structure
Past Continuous The LONG background action. was/were + verb(ing)
Simple Past The SHORT action that interrupts. verb(ed) / irregular

Key Words: When vs. While

While / As usually come before the long action (Past Continuous).

  • While the scientist was working, he made a discovery.

When usually comes before the short action (Simple Past).

  • The children were playing games when the lights went out.
*Note: Sometimes "When" is used before the continuous tense in casual speech (e.g., "When I was surfing..."), but "While" is the most accurate for continuous actions!

A Very Unlucky Day

Put the verbs in brackets in the correct tense (Past Continuous or Simple Past).

We had a very unlucky day yesterday:

- When my mother (do) the laundry, the washing machine suddenly (stop) .

- I (buy) some CDs at the store when someone (steal) my wallet.

- My father (work) on his computer when the memory (go) out.

- While my elder brother (take) some pictures, he (drop) his new digital camera.

- My younger sister (watch) TV when the electricity (go) out.

- My younger brother (have) a bad accident while he (drive) and (talk) on his cell phone.

- When my elder sister (vacuum) , she (have) a bad electric shock.