Talk about general truths and facts: the Zero Conditional.

The zero conditional talks about things that are always true — scientific facts, general truths, and fixed rules. Both parts use the present simple: "If you heat water, it boils." Unlike the First Conditional, this isn't about a possible future — it's about something that's true every single time.

Why this matters This lesson connects directly to your progress: it covers form: if + present simple, present simple; instructions and rules; telling zero and first conditional apart. Mastering this content lets you move forward confidently, and reinforces patterns you'll use again later. Take time to review every example before moving to the assessment — repetition is what actually locks knowledge in long-term.

01

What will you be able to do?

The goals of this lesson.

02

Before you start

You already know how to talk about specific future possibilities. This lesson covers something different: rules and facts that are always true, no matter when — the Zero Conditional ("If you heat water, it boils").

03

Form and general truths

Both the "if" clause and the result clause use the present simple. This structure describes something that is always true — not a possibility, a certainty.

PartTenseExample
If clausepresent simpleIf you heat water,
Result clausepresent simpleit boils.

Examples

If you heat water to 100°C, it boils.
Scientific fact
If you mix blue and yellow, you get green.
General truth
If people don't drink water, they get dehydrated.
General truth
Plants die if they don't get sunlight.
General truth (reversed order)
If the temperature drops below zero, water freezes.
Scientific fact
Metal expands if you heat it.
Scientific fact (reversed order)

04

Instructions and rules

The Zero Conditional is also common for fixed rules, instructions, and things that always happen the same way in a system or a routine.

Examples

If you press this button, the machine turns on.
Instruction
If you don't have a ticket, you can't enter.
Rule
If you're under 18, you need an adult with you.
Rule
If the light is red, you stop.
Rule
If you finish early, you can leave.
Rule
If the alarm goes off, everyone leaves the building.
Instruction

05

Zero vs. First Conditional

These two are easy to confuse because they look similar. The difference is simple: Zero Conditional describes something always true; First Conditional describes one possible, specific future situation.

Examples

If you heat ice, it melts.
Zero — always true
If it rains tomorrow, I will stay home.
First — one specific future
If children eat too much sugar, they get hyper.
Zero — always true
If she eats that whole cake, she'll feel sick.
First — one specific future
If you don't sleep enough, you feel tired.
Zero — always true
If I don't sleep tonight, I'll be tired tomorrow.
First — one specific future
Ice melts if the temperature rises.
Zero — always true (reversed)
If the temperature rises this week, the snow will melt.
First — one specific future
If you don't pay the bill, the service stops.
Zero — a fixed rule
If you don't pay this month's bill, they'll cut the service.
First — one specific future

06

Reading

Read the text and answer the questions. You can try as many times as you want.

Mr. Davis is explaining the lab safety rules to his new students. "If you don't wear your safety glasses, you can't use the equipment," he says. "And remember: if you heat this chemical too fast, it reacts violently, so always go slowly."

He also reminds them of a basic fact: if metal gets hot enough, it changes color, so they can use color to estimate temperature safely. "If the alarm rings, everyone leaves immediately — no exceptions," he adds. "These rules exist because they're true every time, not just sometimes."

1. What happens if you don't wear safety glasses?

2. What happens if you heat the chemical too fast?

3. What can students use to estimate temperature?

4. What happens if the alarm rings?

5. Why do these rules exist, according to Mr. Davis?

💪 You can now describe facts and rules that are always true — and tell them apart from a specific future possibility. Keep going with B1!

07

Fill in the Blanks

Usa las pistas para completar cada palabra en inglés. Sin calificar — repite las veces que quieras.

08

Key Points

The essentials of this lesson, summarized.

09

Vocabulary in This Lesson

Key terms to remember.

boils
/bɔɪlz/

reaches the temperature at which liquid turns to gas

hierve
"If you heat water to 100°C, it boils."
freezes
/ˈfriː.zɪz/

becomes solid because of low temperature

se congela
"If the temperature drops below zero, water freezes."
dehydrated
/ˌdiː.haɪˈdreɪ.tɪd/

lacking enough water in the body

deshidratado/a
"If people don't drink water, they get dehydrated."
expands
/ɪkˈspændz/

becomes larger in size

se expande
"Metal expands if you heat it."
hyper
/ˈhaɪ.pər/

overly excited or energetic

hiperactivo/a
"If children eat too much sugar, they get hyper."
rings
/rɪŋz/

makes a clear ongoing sound, like a bell

suena (timbre, alarma)
"If the alarm rings, everyone leaves immediately."

10

Build the Sentence

Tap the words in the correct order to form the sentence. Ungraded — repeat as many times as you like.

11

Choose the Correct Verb

Tap the correct verb form to complete each sentence. The other options are conjugations from other tenses — on purpose, so you learn to tell them apart.

If you water it boils

If the temperature drops below zero, water

If you this button, the machine turns on

If the alarm , everyone leaves the building

Plants if they don't get sunlight

13

Assessment

You need at least 80% to unlock the next lesson. You can retake it as many times as you want — your best score is saved.

1. "If you heat water to 100°C, it boils." — which one is correct?

2. What does this mean: "If you press this button, the machine turns on."?

3. Select the correct match for: "If you heat ice, it melts."

4. What does this mean: "If it rains tomorrow, I will stay home."?

5. "If you don't have a ticket, you can't enter." — which one is correct?

6. What does this mean: "If you don't drink water, you get dehydrated."?

7. Select the correct match for: "If the alarm rings, everyone leaves the building."

8. What does this mean: "If she eats that whole cake, she'll feel sick."?

9. "Metal expands if you heat it." — which one is correct?

10. What does this mean: "If you don't pay the bill, the service stops."?

Review — Lesson 35 What matches: "I used to play soccer every weekend."?

Review — Lesson 34 What matches: "I was working when she called."?

14

Summary and next step

You now describe facts and rules that are always true with the Zero Conditional. Next lesson: the First Conditional, for real future possibilities.

🗣️ Practice out loud

Use the conversational tutor to practice this topic.

Open the tutor

15

Games

Practice this lesson's vocabulary with a word search and flashcards. Ungraded — play as many times as you like.

Word Search

Tap the first and last letter of a hidden word to find it. Los términos de varias palabras van sin espacios en el tablero (ej. "give up" aparece como GIVEUP).

Flashcards

Elige la respuesta correcta. Si aciertas, la tarjeta queda lista por hoy; si fallas, vuelve a aparecer pronto para reforzarla. Tu progreso se guarda en este dispositivo.

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