yòng kuàizi jiā dòufu.

用 means to use / with here. It introduces the tool or means used to do the action.

So the structure is:

用 + tool + verb + object

In this sentence:

• 用筷子 = using chopsticks / with chopsticks
• 夹豆腐 = pick up tofu

A very natural English pattern would be use chopsticks to pick up tofu.

The sentence follows this pattern:

用 + instrument + verb + object

So:

• 用 = use
• 筷子 = chopsticks
• 夹 = pick up / pinch / grasp between
• 豆腐 = tofu

Literally, it is something like:

Use chopsticks pick up tofu.

This kind of ordering is normal in Mandarin.

Mandarin often leaves out the subject when it is obvious from context.

So 用筷子夹豆腐。 could mean different things depending on the situation:

• Use chopsticks to pick up tofu. (instruction/command)
• [Someone] uses chopsticks to pick up tofu.
• [You] pick up tofu with chopsticks.

If the subject is clear, Chinese often does not say it.

It can work as a complete sentence in context, especially as:

• an instruction
• a step in directions
• a short description

For example, in a textbook or during a lesson, 用筷子夹豆腐。 can naturally mean:

Use chopsticks to pick up the tofu.

In very formal writing, you might expect more context or an explicit subject, but in everyday Chinese this kind of short sentence is common.

夹 specifically means to grip, clamp, or pick up by pressing from two sides. That makes it a very good verb for using chopsticks.

Compare:

• 夹 = pick up by pinching/clamping, especially with chopsticks
• 拿 = take / hold / pick up in a general sense

So:

• 用筷子夹豆腐 sounds natural
• 用筷子拿豆腐 is less natural because chopsticks do not usually hold things in the broad sense; they grip them

筷子 normally refers to chopsticks as a pair, just like English usually says chopsticks in the plural.

If you want to count them, you often say:

• 一双筷子 = one pair of chopsticks

In the sentence 用筷子夹豆腐, 筷子 just means chopsticks in general.

Measure words are usually needed when you are counting or specifying something, such as:

• 一双筷子 = one pair of chopsticks
• 一块豆腐 = a piece of tofu

But in 用筷子夹豆腐, the nouns are being used in a general way:

• 筷子 = chopsticks
• 豆腐 = tofu

So no measure word is needed here.

Mandarin does not use articles like a, an, or the the way English does.

So 豆腐 can mean:

• tofu
• the tofu
• some tofu

The exact meaning depends on context.

Likewise, 筷子 can mean:

• chopsticks
• the chopsticks
• some chopsticks

Chinese often leaves this kind of information unstated unless it matters.

In this sentence, 用 is often taught as a verb meaning to use, but in sentences like this it behaves very much like a coverb or preposition-like word introducing the instrument.

So 用筷子 means:

with chopsticks / using chopsticks

Then the main action is:

夹豆腐 = pick up tofu

So functionally, 用筷子 tells you how the action is done.

Usually, no—not if you want the same meaning.

用筷子夹豆腐 clearly means:

use chopsticks to pick up tofu

But 筷子夹豆腐 sounds like chopsticks pick up tofu or chopsticks clamp tofu, which is awkward because 筷子 looks like the subject.

So 用 is important here because it marks 筷子 as the instrument.

It could, but the sentence would have a slightly different structure.

Your sentence:

• 用筷子夹豆腐。
• simple and direct

Another possible form:

• 用筷子把豆腐夹起来。
• pick up the tofu with chopsticks

The 把 structure is often used when the object is being handled, moved, or affected in a clear way.

So:

• 用筷子夹豆腐 = perfectly fine, simple statement/instruction
• 用筷子把豆腐夹起来 = more explicit about lifting the tofu up

In careful dictionary-style pinyin, you may see kuàizi, and in actual speech the 子 is very often pronounced with a neutral tone.

So it is commonly heard as:

• kuài zi

not a strong full third tone on 子.

This is very common with nouns ending in 子.

By itself, 豆腐 is general and flexible. It can refer to:

• tofu as a food
• some tofu
• the tofu in the situation

If you want to be more specific, you could say things like:

• 一块豆腐 = a piece of tofu
• 这块豆腐 = this piece of tofu
• 那个豆腐 = that tofu

In 用筷子夹豆腐, it just means tofu, with the exact interpretation coming from context.

Yes. Without 了, the sentence sounds more like:

• a general action
• an instruction
• a habitual description

For example:

• 用筷子夹豆腐。 = use chopsticks to pick up tofu / pick up tofu with chopsticks

With 了, it could indicate completion or a new situation, but you would usually want more context, such as:

• 用筷子夹了豆腐。 = picked up some tofu with chopsticks

That sounds more like reporting an action that happened.

So the version without 了 is better for a simple textbook example or instruction.

Yes. In the right context, it can sound like a short instruction:

用筷子夹豆腐。
= Use chopsticks to pick up the tofu.

If you want to make the command sound more clearly directed at someone, you could add:

• 你用筷子夹豆腐。 = You use chopsticks to pick up the tofu.
• 用筷子夹豆腐吧。 = Use chopsticks to pick up the tofu.
• 请用筷子夹豆腐。 = Please use chopsticks to pick up the tofu.

So the basic sentence is short, but very usable.