For the first activity I use a lesson from the American Chemical Society. It uses materials that are inexpensive and easy to obtain and is presented in an simple to follow format with video and animation for support.
The lesson can be found at their Middle School Chemistry website.
You will need metal washers (8-10 per group), string, styrofoam cups, a source of hot water and cool water and thermometers.
One of the great elements to this lesson are the visuals that help students construct an image of what molecules are doing when you heat or cool them.
The website includes handouts and readings. I have included them here for you as well.
Disciplinary Core Ideas:
Energy and Matter
If you follow the lesson as it is laid out on the website, I found it to take two full 55 minutes class periods.
Day 1: Have students explore and explain what happens when 1) room-temperature metal is placed in hot water and 2) hot metal is placed in room temperature water
Day 2: Watch videos of molecular models and create their own molecular models of heat transfer by conduction from this lab and discuss the connection between molecular motion, temperature, and conduction.
I also like the extension portion of this lesson which has students touch the metal part of their chairs and the plastic parts of their chairs. It begins a great discussion of why some materials are better conductors or insulators which will be useful in an upcoming lesson on designing a thermos.
I recommend focusing on the post discussion if this lab and eliciting student ideas. You are laying important groundwork in these early lessons to help students dig into heat and temperature more than just running through a series of labs.
Below is a video of students making meaning of heat transfer by means of conduction using this model.
Before students leave for the day ask them to write down an example of this type of heat transfer from their everyday life.
Use the results of these responses as a formative assessment to adjust the how you progress from this lesson. If student thinking is not clear than consider following up the next day with a summary. Since we will continue to come back to conduction many more times, looking at different models related to Earth systems, it's a good ideas to build a solid foundation of heat transfer early on.