Na dywanie leży jeden klocek, a reszta klocków jest w pudełku.

Because after na when it means on in a location sense, Polish uses the locative case.

• dywan = carpet/rug
• na dywanie = on the carpet

Compare:

• na dywanie = on the carpet, located there
• na dywan = onto the carpet, movement toward it

So in this sentence, nothing is moving onto the carpet; the block is already there, so na dywanie is correct.

It changes because it is in the locative singular, required after na for location.

The dictionary form is:

• dywan = carpet

Locative singular:

• na dywanie = on the carpet

This is a normal noun case change in Polish. A learner should get used to the idea that nouns often change form depending on their role in the sentence.

Leży means is lying or lies, so it gives a more specific physical description than jest.

• leżeć = to lie
• leży = lies / is lying

So:

• Na dywanie leży jeden klocek = One block is lying on the carpet.

If you said Na dywanie jest jeden klocek, it would still be understandable and natural in many situations, but leży emphasizes position: the block is physically lying there.

Polish often uses verbs like:

• stać = stand
• siedzieć = sit
• leżeć = lie

where English often just says is.

Yes, it can often be omitted, depending on what you want to emphasize.

• jeden klocek = one block
• klocek = a block / block

In this sentence, jeden is useful because it contrasts with the rest of the blocks:

• one block is on the carpet,
• the rest are in the box.

So jeden helps create that contrast clearly.

Klocek usually means a block, especially a toy block or building block.

It can refer to:

• a wooden block
• a toy brick
• a construction block like a LEGO-type piece, depending on context

In this sentence, the most natural interpretation is a toy building block.

After reszta meaning the rest, Polish normally uses the genitive.

So:

• reszta = the rest
• klocki = blocks
• klocków = of blocks

That is why:

• reszta klocków = the rest of the blocks

This is similar to English the rest of the blocks, where Polish expresses the of relationship through the genitive case instead of a separate word.

Because the grammatical subject is reszta, which is singular.

Even though klocków refers to multiple blocks, the main noun controlling the verb is:

• reszta = the rest

So Polish uses a singular verb:

• reszta klocków jest w pudełku

This is similar to English, where some speakers also say the rest is... depending on how they view the group, though English is less strict here.

Klocków is the genitive plural form of klocek.

Basic forms:

• klocek = block
• klocki = blocks
• klocków = of blocks

It appears here because reszta requires the following noun to be in the genitive:

• reszta klocków = the rest of the blocks

So this is not just a plural form; it is specifically the plural form used after reszta.

Because w meaning in takes the locative case when it refers to location.

• pudełko = box
• w pudełku = in the box

Just like:

• na dywanie = on the carpet
• w pudełku = in the box

Both are location phrases, so both nouns appear in the locative.

Yes. Polish word order is more flexible than English, although different orders can change emphasis.

The sentence:

• Na dywanie leży jeden klocek, a reszta klocków jest w pudełku.

is very natural. It starts with the location on the carpet, then introduces what is there.

Other possible orders include:

• Jeden klocek leży na dywanie, a reszta klocków jest w pudełku.
• Reszta klocków jest w pudełku, a na dywanie leży jeden klocek.

These all mean roughly the same thing, but the focus shifts depending on what comes first.

Here a links two parts of the sentence and means something like and, while, or whereas.

• ..., a ... often introduces a contrast or comparison.

So here it means:

• One block is on the carpet, while the rest of the blocks are in the box.

It is not exactly the same as i.

• i = and, simple addition
• a = and/but/while, often with contrast

In this sentence, a is appropriate because the sentence contrasts two locations.

Yes. Klocek is a masculine inanimate noun.

You can tell from forms like:

• jeden klocek
• ten klocek
• klocków

This matters because adjectives, numerals, and sometimes verb forms must agree with the noun’s gender and number.

For example:

• jeden klocek = one block
• dwa klocki = two blocks

Learning the gender of nouns is important in Polish because it affects many other words in the sentence.