Leviticus teaches that sin is when the soul sins against the Word or Law of God and to be unclean is when your old man, or the part of you that you can see, becomes abnormal.
Sin is a violation of the Law. Uncleanness is when your body is abnormal.
To be normal is to not have any sickness or disease nor to have any flow of blood (Leviticus 12); blisters on the skin (Leviticus 13) or bodily discharges (Leviticus 15)..
Thus a state of abnormal is when these items occur. When you become unclean you are unable to worship God at the Tent of Meeting and to be relegated to life outside camp meaning you are severed, temporarily, from your family and friends.
To become clean means your privilege to worship God at Tent of Meeting is restored and you are allowed to live again inside the camp with your family in the midst of your friends.
As sin separates us from God and must be atoned for to restore the relationship to be unclean also separates us from God and family and there must also be an atonement to become clean again.