IN
ON
UNDER
100

They are in your mouth. If you brush them, they are clean and white. 

teeth

100

In winter you put it on your head. It keeps you warm.

a hat / a cap

100

It is under your nose

mouth

200

It's in your pencil case. You use it for writing.

pen/pencil

200

You wear them on your feet in the summer.

sandals / flip-flops

200

This animal leaves underwater. It looks like a star. What is it?

a starfish
300

It is in your body and it pumps blood.

heart

300

You put them on your hands in winter. They keep you warm.

gloves / mittens

300

This animal lives underwater. It's a mammal. It's the biggest animal in the seas/oceans. 

a (blue) whale

400

It is an organ inside your head. It controls you.

the brain

400

It's on your head. It can be long or short, curly or straight, blond, brown, black or ginger.

hair

400

It's a vegetable. It grows under the ground. It can make you cry when you chop it.

an onion

500

It is in an organ your body and it helps you breath.

lungs

500

They are on your fingertips. They are hard. You need to cut them from time to time. Some women like to paint them.

nails

500

It's a military ship. It travels under the sea.

a submarine