The short answer: Yes, ELB's IP addresses (both the ones that are publicly distributed to clients of your service, and the internal IPs from which ELB sends traffic to your instances) dynamically change.

Does AWS ELB have an IP address?

These are the IP addresses where the clients should send the requests that are destined for the load balancer. However, Classic Load Balancers and Application Load Balancers use the private IP addresses associated with their elastic network interfaces as the source IP address for requests forwarded to your web servers.

Does alb have IP address?

Today, the only way to achieve static IP addresses for your application behind an ALB is to add another layer in between the client and your ALB which does have a static IP address, and then forward requests to your ALB.