This must have been asked before but I can't find an answer.
SCENARIO: It takes ten minutes to add a new block of data to the blockchain. Larry has one bitcoin. He goes to the mall and within one ten minute period between blocks:
1) Larry spends most of his bitcoin at a computer store.
2) Larry runs next door to a jewelry store, where he again spends most of his bitcoin.
Obviously this can't happen. What is the mechanism that prevents double spending within the ten minutes between blocks?
Thanks.