Google forms are great for conducting surveys or collecting information on prior knowledge.. You can create them and submit them in a browser (Chrome works best). To get better functionality of any Google Apps I suggest using the browser version rather than the apps. See the Overview page for how best to do this.
Mindmapping apps can be used at this stage to brainstorm what is known (prior knowledge) and what students need to find out. Questions can easily be sorted using these apps. Graphic organisers like a KWH (What I Know, What I want to find out, How I will find out) chart. can be created with the apps.
Socrative - teacher a student response system. A question or prompt is given and students log in to the class and respond. Responses are collated. In this stage it can be used for brainstorming. Can also be used to generate responses for a KWH chart. Create a teacher account here. You can use this in a browser as well as the app. More info here.
Socrative - student - Students type in the room number you give them and can answer questions you set using the app or in a browser. More info here.
Voicethread - 5 free voicethreads or can upgrade to unlimited account. Upload media eg image, document, slideshow and comments can be made around it via text, audio or video recording. Useful tips. Example 1 - kindergarten students discuss trout Example 2 - 5 year olds discuss why the sun is important. Example 3 - 10 year olds debate whether money should be spent on space or Earth's problems.
Lino - sticky notes - can add images to notes.Has ads in the free version. More info here.
StickyBoard2 - Whiteboard with sticky notes, can move notes around and add written notes. One board with free version but can screenshot and save. Single colour notes. Paid version $6.99 allows for coloured notes and a gallery to save multiple boards. Also allows export as an image or pdf. Integrates with a number of other apps. More info here.
Book Creator - $6.49. Can write, draw and record (see the Act and Share page for similar apps). You can try the free version first - makes one book. More info here.
Socrative - student - see above.
Socrative - teacher - see above.
- Review of Android mindmapping Apps
These are the free versions, most have a paid version with extra features.