guìzhòngwùpǐn zài fángchéndài lǐ.

In Mandarin, you usually do not use 是 to connect a noun to a location.

So instead of saying something like Valuables are in the dust bag with a separate verb are, Chinese normally uses:

贵重物品 在 防尘袋里。

Pattern: thing + 在 + place

So 在 is doing the job of showing where something is.

• 他在家。 = He is at home.
• 书在桌子上。 = The book is on the table.

Using 是 here would sound unnatural.

Here, 在 means to be at / in / on a place.

It marks location.

In this sentence:

• 贵重物品 = valuables
• 在 = are located at / in
• 防尘袋里 = inside the dust bag

So 在 tells you where the valuables are.

They work together, but they do different jobs.

• 在 introduces the location
• 里 means inside and comes after the place noun

So:

• 在防尘袋里 = in/inside the dust bag

You can think of it as:

• 在 = at/in
• 里 = inside

This is a very common Chinese pattern:

• 在房间里 = in the room
• 在包里 = in the bag
• 在车里 = in the car

Sometimes 里 can be omitted if the meaning is obvious, but with containers like bags, keeping 里 sounds very natural.

里 here is a localizer.

A localizer is a word that comes after a noun and gives a more exact spatial meaning, such as:

• 里 = inside
• 上 = on, above
• 下 = under
• 前 = in front
• 后 = behind

Examples:

• 桌子上 = on the table
• 椅子下 = under the chair
• 房子里 = inside the house

So 防尘袋里 literally means inside the dust bag.

贵重物品 means valuables or valuable items.

It can be broken down like this:

• 贵重 = valuable, precious
• 物品 = articles, items, goods

Together, it means things that are important or expensive enough to need care, such as:

• jewelry
• cash
• passports
• watches

It is a common phrase in signs, instructions, hotel notices, and travel contexts.

It is usually understood as a collective or plural-like expression, similar to valuables in English.

Chinese nouns usually do not change form for singular vs. plural the way English nouns do.

So 贵重物品 can mean:

• valuable item
• valuable items
• valuables

The exact meaning depends on context.

In most real-life situations, people understand it as valuables.

防尘袋 means dust bag or protective dust bag.

It breaks down as:

• 防 = prevent against
• 尘 = dust
• 袋 = bag

So it is literally a bag used to protect something from dust.

You often see this for:

• handbags
• shoes
• luxury items
• stored accessories

Because there is no number or demonstrative before the nouns.

Chinese measure words usually appear when you say things like:

• 一个防尘袋 = one dust bag
• 这个防尘袋 = this dust bag
• 一些贵重物品 = some valuable items

But in the sentence:

贵重物品在防尘袋里。

the speaker is just making a general statement about where the valuables are, so no measure word is needed.

Yes. 里面 is also natural.

• 里 = inside
• 里面 = inside, the inside part

So these are both fine:

• 贵重物品在防尘袋里。
• 贵重物品在防尘袋里面。

The version with 里面 can sound a little fuller or slightly more explicit, but the meaning is basically the same.

Chinese often puts the thing first and then tells you its location.

Basic pattern: subject + 在 + place

So:

• 贵重物品 = the thing being talked about
• 在防尘袋里 = its location

This is very normal Chinese word order for location statements.

Yes, and that is also a very natural sentence, but the focus is a little different.

• 贵重物品在防尘袋里。
  = The valuables are in the dust bag.
  Focus: where the valuables are

• 防尘袋里有贵重物品。
  = There are valuables in the dust bag.
  Focus: what is in the dust bag

So both are correct, but they answer slightly different questions.

It should be read as four syllables:

• guì
• zhòng
• wù
• pǐn

So the full sentence is:

• guì zhòng wù pǐn
• zài
• fáng chén dài
• lǐ

Even when pinyin is written together for a word, it still contains separate syllables. Chinese pronunciation is syllable-based, so it helps to split it up when learning.

Yes, in casual speech people may say 袋子 for bag, so 防尘袋子 is understandable.

However, 防尘袋 is the more standard and compact form, especially in labels, product descriptions, or formal wording.

So:

• 防尘袋 = standard and common
• 防尘袋子 = understandable, a bit more conversational

Yes. It sounds natural, especially in practical contexts such as:

• travel
• packing instructions
• product care
• storage reminders
• store or hotel notices

It has a slightly concise, practical tone, which is very common in written Chinese and spoken instructions.