Gastric juice is a digestive fluid secreted by the stomach. It is primarily composed of hydrochloric acid, which makes it very acidic with a pH value of about 2. Additionally, gastric juice contains enzymes such as pepsin, which is responsible for breaking down proteins. Therefore, it can be concluded that gastric juice contains enzymes and is acidic. It is not a mixture of substances, and it does not have a pH value of 7, which is neutral.