Properties of Yeast

You crawl through the back door
and knock on the side of my cell phone.
I wake in the hive of mornings to
your voice, swooning security that
keeps these tiny feet grounded,
whether in folds of cotton, pinafore,
or six feet under.

You're in my old shoeboxes,
at the top of a fresh bowl of rice.
I find you at home in my shower curtains,
the backseat of the car and
in pockets of bubblewrap.

The breathless of laughter keeps
the world warmer, as air is preserved
and there's just more
room for us to breathe.

Empty spaces are only ever
filled with God and
monoxide.

Nicely done

I really have nothing to say, which makes this critique rather meaningless. But hey I'm raising it up for you to possibly get a critique that actually "says" something hehe.

One thing, the last stanza, utterly amazing ending

Keep it going like that,

Cheerios, Chandni

You crawl through the back door
and knock on the side of my cell phone.
I'm not sure why someone would knock on the side of a cell phone. If it's to get someone's attention, that's quite an original way to do it
I wake in the hive of mornings to
your voice, swooning security that
swooning security: nice. I don't know what a hive of mornings is, but the safe, enclosed space it connotates fits well with the "swooning security" of the next line.
keeps these tiny feet grounded,
whether in folds of cotton, pinafore,
Did you mean to offset pinafore with commas? If you mean to continue the list that you began with cotton, "pinafore" should be changed to "pinafores" to make it plural. Or you could change it to "a pinafore". Additionally, as a pinafore is similar to an apron, I'm not sure why a person's feet would be folded in one
or six feet under.
Until now, I had pictured something along the lines of a sunny day in the country. After this line, it was like in the movies when the image suddenly inverts to negative. It was cool, but did you mean for that to happen?

You're in my old shoeboxes,
at the top of a fresh bowl of rice.
My brain stumbled at this line because there are alot of short words; it sounded choppy in my head
I find you at home in my shower curtains,
the backseat of the car and
Here, I would suggest moving "and" to the next line, following the established pattern. Leaving "and" at the end of the line creates an unnatural pause, as a child might use when telling a long story; while that's good to use when a poem is in the voice of a child, it doesn't fit here.
in pockets of bubblewrap.
All of these examples seem random and unconnected to me, as if they're just a list. I also don't see how they connect to God or monoxide (as stated at the end). Maybe it would be stronger if they followed a theme [such as things you'd find in a kitchen since the title is "Properties of Yeast"].

The breathless of laughter keeps
Did you mean "breathlessness" here?
the world warmer, as air is preserved
and there's just more
room for us to breathe.
This is a funny [in a good sense] idea.

Empty spaces are only ever
filled with God and
Here, I like how "and" is placed at the end of a line because it's drawing out a conclusion.
monoxide.
I'd suggest eliminating the space between the last two stanzas since each is only one thought/sentence whereas the other stanzas seem to connect two thoughts.

PM me if you need anything
-Amelia