CH02: minor edits for consistency, voice, and correctness

ch02.asciidoc

@@ -435,16 +435,16 @@ output. Alice will therefore "encumber" the output value with a demand
 for a signature from Bob.
 
 This transaction will also include a second output, because Alice's
-funds are contain more money than the cost of the
+funds contain more money than the cost of the
 podcast. Alice's change
 output is created in the very same
 transaction as the payment to Bob. Essentially, Alice's wallet breaks
-her funds into two payments: one to Bob and one back to herself. She can
-then use (spend) the change output in a subsequent transaction.
+her funds into two outputs: one to Bob and one back to herself. She can
+then spend the change output in a subsequent transaction.
 
 Finally, for the transaction to be processed by the network in a timely
 fashion, Alice's wallet application will add a small fee. This is not
-explicit in the transaction; it is implied by the difference between
+explicit in the transaction; it is implied by the difference in value between
 inputs and outputs.  This _transaction fee_ is collected by the
 miner as a fee for validating and including the transaction in a block
 to be recorded on the blockchain.
@@ -462,7 +462,7 @@ contains everything necessary to confirm ownership of the funds and
 assign new owners. Now, the transaction must be transmitted to the
 Bitcoin network where it will become part of the blockchain. In the next
 section we will see how a transaction becomes part of a new block and
-how the block is "mined." Finally, we will see how the new block, once
+how the block is mined. Finally, we will see how the new block, once
 added to the blockchain, is increasingly trusted by the network as more
 blocks are added.
 
@@ -584,10 +584,11 @@ lottery to create the next block.
 
 Jing started mining in 2010 using a very fast desktop computer to find a
 suitable Proof-of-Work for new blocks. As more miners started joining
-the Bitcoin network, the difficulty of the problem increased rapidly.
+the Bitcoin network, the Bitcoin protocol automatically increased the
+difficulty of finding a new block.
 Soon, Jing and other miners upgraded to more specialized hardware, such
 as high-end dedicated graphical processing units (GPUs) cards such as
-those used in gaming desktops or consoles. At the time of this writing,
+those used in gaming desktops. At the time of this writing,
 the difficulty is so high that it is profitable only to mine with
 ((("application-specific integrated circuits
 (ASIC)")))application-specific integrated circuits (ASIC), essentially