Hi Chipsmum, welcome to the board.
If Chip has come from a home where it was quite in the evening he could be a bit upset. It's good if you keep a chipmunk where there are people during the day, but in the evening they like to get to sleep early. They tend to go off to their nests about 5pm this time of year, but stay awake until at least 9pm. But they easily get spooked in their nests if there is noise outside their home. So during the day chipmunks like to see someone around but in the evening and through the night they like it quiet.

Some owners say to avoid sawdust, as the fine particles can clog up their noses. I find the wood type cat pellets work fine, but never use the synthetic cat pellets which absorb moisture. If a chip swallows these you could end up with an expensive vets bill. So i use wood cat pellets or wood chips, which i cover liberally with meadow hay.