B. Foundations of Language · Foundations: Grammar, Sentences and Punctuation

Building Complex Sentences from Phrases and Clauses

B3.1 B3.3 A3.1About 45 minutes

Learning goals

I can combine several short sentences into one clear sentence using phrases and clauses.
I can choose a phrase or a clause to show a relationship such as cause, contrast, time or purpose.
I can turn a clause into a phrase (and a phrase into a clause) to change the rhythm of my writing.
I can combine sentences in science and social studies writing so the ideas connect.

Words to know

sentence combining
Joining two or more short sentences into one sentence by turning some of them into phrases or clauses.

prepositional phrase
A phrase that starts with a preposition (in, on, after, during, despite, because of) and ends with a noun or pronoun: during the storm.

participial phrase
A phrase that starts with an -ing or -ed/-en verb form and describes a noun: Covered in snow, the car...

appositive
A noun or noun phrase that renames the noun beside it: Ms. Diaz, our coach, ...

infinitive phrase
A phrase that starts with to + a verb: to win the game.

Four sentences, one idea

Jordan finished his project. He worked late. He used a hot glue gun. The project was about wind turbines.

These sentences are correct, but they bump along. Watch what happens when we fold them together:

Working late with a hot glue gun, Jordan finished his project about wind turbines.

One sentence, every idea, and it reads smoothly. The Grade 7 curriculum asks you to create complex sentences that combine phrases and clauses to express relationships among ideas. That's exactly what we just did.

Four short sentences (dashed boxes) fold into one. Two become a participial phrase, one stays as the main clause, and one shrinks to a prepositional phrase.

Your tools

You already know these tools from earlier grades. Now you'll use them together.

Dependent clause (has a subject and verb): because the roads were icy
Prepositional phrase: because of the icy roads, after lunch, despite the cold
Participial phrase: Shivering in the wind, ..., Built in 1890, ...
Appositive: Mr. Okafor, our principal, ...
Infinitive phrase: to save energy

The same relationship can often be shown by a clause or by a phrase. Phrases are shorter; clauses give more detail.

Relationship	With a clause	With a phrase
Cause	Because the roads were icy, school was cancelled.	Because of the icy roads, school was cancelled.
Contrast	Although it was cold, we finished the race.	Despite the cold, we finished the race.
Time	After we ate dinner, we washed the dishes.	After dinner, we washed the dishes.
Purpose	We turned off the lights so that we could save energy.	We turned off the lights to save energy.
Description	The trail, which was covered in ice, was closed.	The trail, covered in ice, was closed.

One relationship, two ways to show it

Phrase or clause?

Watch out for because and because of. Because starts a clause (it needs a subject and verb after it: because it rained). Because of starts a phrase (it needs only a noun: because of the rain). The same goes for although (clause) and despite (phrase). Never write despite it rained.

Because and although need a whole clause after them. Because of and despite need only a noun. That is why despite it rained is wrong.

Worked example

Let's combine sentences in a science paragraph

Combine into one sentence: The sun heats water in lakes and oceans. The water evaporates. The water vapour rises. It cools and condenses into clouds.

What's the relationship? The sun's heat causes evaporation, and then things happen in order.
Make the cause a dependent clause: When the sun heats water in lakes and oceans,
Join the actions of the same subject in one main clause: the water evaporates, rises as water vapour and cools
Show the last step with a participial phrase: , condensing into clouds.

When the sun heats water in lakes and oceans, the water evaporates, rises as water vapour and cools, condensing into clouds. (Another good answer: Heated by the sun, water in lakes and oceans evaporates; the water vapour rises, cools and condenses into clouds.)

Worked example

Let's combine sentences in a history paragraph

Combine: Ms. Tran is our history teacher. She showed us an old map. The map was of our town. It was drawn in 1880.

Ms. Tran is our history teacher renames Ms. Tran → make it an appositive: Ms. Tran, our history teacher,
The map was of our town → prepositional phrase: of our town
It was drawn in 1880 describes the map → participial phrase: drawn in 1880

Ms. Tran, our history teacher, showed us an old map of our town drawn in 1880.

Don't over-combine

A good combined sentence is clear. If you have to read it twice, it's too long. Read it aloud. If you run out of breath, split it or use a semicolon (you'll learn more about semicolons later in this unit).

Just for fun

Combining sentences is like making a smoothie: toss in four choppy sentences, blend with phrases and clauses, and pour out one smooth sentence. Just remember to put the lid on (a period).

Hands-on activity

Sentence-combining kitchen challenge

You need: a recipe card or the instructions on a box of food, paper and a pencil, and a family member.

Copy 4 to 6 short instruction sentences, like Preheat the oven. Mix the flour and sugar. Add the eggs.
Combine them into 2 or 3 sentences using phrases and clauses. Example: While the oven preheats, mix the flour and sugar, then add the eggs.
Read both versions aloud to your family member. Which is easier to follow while cooking? (Sometimes short sentences are better for instructions!)
Now pick a paragraph from your science or social studies notes and combine sentences there too.

Safety: Only use the oven or stove with a grown-up. This activity is about the writing; you don't need to cook.

What to look for: each combined sentence keeps every idea, uses correct commas, and shows the relationship (time, cause, contrast or purpose).

Your turn

Combine using because of: The game was postponed. There was a thunderstorm.

Combine using despite: We were tired. We kept paddling.

Combine using an appositive: Dr. Singh is our dentist. She gave me a new toothbrush.

Combine using an infinitive phrase: We went to the library. We wanted to borrow a book about bridges.

Combine using a participial phrase: The puppy was soaked from the rain. It shook itself on the mat.

Change the clause to a phrase: After we finished the test, we had recess.

More practice: warm-up

Phrase or clause? during the assembly

Phrase or clause? while the band played

Name the phrase type: to catch the early bus

Name the phrase type: our neighbour in Mrs. Petrov, our neighbour, shovels our driveway.

Which is correct: Because of the snow or Because the snow?

More practice: on your own

Combine three sentences into one: Our class planted trees. We planted them along the creek. We wanted to stop erosion.

Rewrite with a clause instead of the phrase: Despite the rain, the parade continued.

Find and fix the error: Despite it was snowing, we drove to Kingston.

Combine to show contrast: Beavers are small. They can change a whole wetland.

Combine using a relative clause and a prepositional phrase: The Rideau Canal runs through Ottawa. It is a UNESCO World Heritage Site.

Challenge

Combine into one or two clear sentences: The storm hit on Tuesday. It knocked out power. Power was out for two days. Our neighbours had a generator. They let us charge our phones.

Write one sentence about a topic you are studying in science or social studies that uses at least one phrase and one dependent clause. Label them.

Show the relationship of condition two ways (with a clause, then with a phrase): You need a permit. You can have a campfire then.

Check your understanding

Quiz

Which phrase means the same as because it was foggy?

Which sentence is correct?

What is the best combined sentence? Ella is our goalie. She stopped every shot.

Which part of this sentence is an infinitive phrase? We saved our allowance to buy a telescope.

Which relationship does so that show?

What's the main reason to combine short sentences?

For parents and teachers

What this lesson is about: sentence combining. Your child folds short sentences into one using clauses and phrases (prepositional, participial, appositive, infinitive) to show cause, contrast, time and purpose. This is a core Grade 7 expectation.

How to help at home:

Take two short sentences from daily life (I'm hungry. Dinner isn't ready.) and challenge each other to combine them in two different ways.
When your child writes for science or social studies, ask: "How are these two ideas related? Can one sentence show that?"

Common difficulties:

Mixing up because (needs a clause) and because of (needs a noun), or although and despite.
Over-combining into a sentence that's hard to follow. Reading aloud helps.
Forgetting the comma after an introductory phrase or clause.