На обед я хочу сварить рис.

На обед means for lunch or for the lunch meal. Russian often puts time-related or context-setting information near the beginning of the sentence.

Starting with На обед gives the sentence a natural topic-comment structure:

• На обед — as for lunch,
• я хочу сварить рис — I want to cook rice.

You could also say:

• Я хочу сварить рис на обед.

That is also correct. The original version just emphasizes lunch a bit more.

Russian uses на with meals in many expressions where English uses for:

• на завтрак — for breakfast
• на обед — for lunch
• на ужин — for dinner/supper

So this is a common pattern you should learn as a set phrase. It does not literally match English preposition use word-for-word.

Also, обед here is in the accusative case, but since it is an inanimate masculine noun, it looks the same as the dictionary form:

• nominative: обед
• accusative: обед

Yes, it could be omitted.

Russian often drops subject pronouns when the verb form already makes the subject clear. Since хочу clearly means I want, you can say:

• На обед хочу сварить рис.

That sounds natural.

Including я is also completely correct. It can make the subject more explicit, add slight emphasis, or simply reflect a neutral speaking style.

After хотеть (to want), Russian normally uses the infinitive of another verb:

• хочу есть — I want to eat
• хочу спать — I want to sleep
• хочу сварить рис — I want to cook/boil rice

So the structure is:

• хочу + infinitive

Here, сварить is the infinitive.

This is an aspect difference:

• варить — imperfective
• сварить — perfective

In this sentence, сварить is used because the speaker wants to cook the rice to completion, as a finished result.

Very roughly:

• варить рис = to be cooking rice / to cook rice in a general or repeated sense
• сварить рис = to cook/boil the rice successfully, to get it done

After хочу, both aspects are possible in Russian, but they mean slightly different things:

• хочу варить рис — I want to be cooking rice / I want to cook rice in general
• хочу сварить рис — I want to cook the rice completely, as a one-time completed action

In this sentence, the perfective сварить is the natural choice.

It is in the accusative, but for an inanimate masculine noun, the accusative often looks exactly like the nominative.

So:

• nominative: рис
• accusative: рис

Because рис is the direct object of сварить, it is in the accusative case, but there is no visible ending change.

Compare that with a feminine noun, where the form often changes:

• каша → кашу

Yes, it is very natural, especially when you mean boil rice or cook rice until it is ready.

Russian often uses more specific cooking verbs than English does. English cook is broad, but Russian may choose different verbs depending on the method:

• варить / сварить — boil, cook by boiling
• жарить / пожарить — fry
• печь / испечь — bake
• готовить / приготовить — prepare, cook more generally

So сварить рис is a very normal and idiomatic choice, because rice is typically boiled.

Yes, you could.

• сварить рис focuses on the cooking method/result: boil/cook the rice
• приготовить рис is more general: prepare/cook the rice

Both are correct, but сварить рис is more specific and often more natural when talking about rice.

Not always.

Traditionally, обед is the main daytime meal, which often corresponds to lunch in English. In many modern contexts, translating it as lunch is the best choice.

However, depending on region, family habits, or context, meal words do not always line up perfectly with English meal terms. So it is best to think of обед primarily as the Russian meal name, which is usually lunch in modern standard usage.

No, Russian word order is relatively flexible.

All of these can work, with slightly different emphasis:

• На обед я хочу сварить рис.
• Я хочу сварить рис на обед.
• Рис я хочу сварить на обед.
• Хочу сварить рис на обед.

The original sentence sounds natural and puts the frame for lunch first. English learners often expect one fixed word order, but Russian uses word order to manage emphasis and information flow more than basic grammar.

Yes. In everyday Russian, many speakers would very naturally say:

• На обед хочу сварить рис.

That is probably the most conversational version.

The full version with я is still correct and natural. It just sounds a little more explicit.