gparted - Ubuntu disk partition split

I am a beginning Linux user and I seem to have run into something of a conundrum.
I am running Ubuntu 14.04 on an HP laptop, dual booted with windows 8.1, with a 500GB harddrive.

It seems that upon installing Ubuntu I have somehow split the partition for Ubuntu in two - and in such a way that I am only left with a measly 15GB of disk space to work with, and a good 160GB doing nothing. The problem is: I do not know how to activate the unused partition. The following GParted screenshot might clarify the issue.

Gparted screenshot of my partitions

The partitions in question are (I believe) sda7 and sda9. (Sda4 is for windows, sda8 is the swap, the rest I don't really know to be honest).

Adding to my confusion is the fact that sda4 does not show up in my disk usage report. The result of df -h is

Filesystem      Size  Used Avail Use% Mounted on

udev            3,9G  8,0K  3,9G   1% /dev
tmpfs           788M  840K  787M   1% /run
/dev/sda7        14G   11G  2,2G  84% /
none            4,0K     0  4,0K   0% /sys/fs/cgroup
none            5,0M     0  5,0M   0% /run/lock
none            3,9G  164K  3,9G   1% /run/shm
none            100M   48K  100M   1% /run/user
/dev/sda9       156G  2,7G  146G   2% /home
/dev/sda2       356M   70M  287M  20% /boot/efi
/dev/sda6       2,0G  2,5M  2,0G   1% /media/berend/HP_TOOLS

So the question is: does anyone know how I can merge my sda7 and sda9 so that I may utilise the full memory capacity? Or otherwise, how can I save & move files to the big sda9 partition?

Many thanks in advance!

kindest regards,

B