Final answer:
Chemicals that alter thinking, perception, and memory are known as psychoactive drugs, including both legal and illegal substances, as well as a category called hallucinogens that specifically alter sensory perceptions.
Step-by-step explanation:
Chemicals that can alter thinking, perception, and memory are called psychoactive drugs. These substances change the function of the brain and result in alterations of mood, thinking, perception, and/or behavior. Psychoactive drugs may be used for therapeutic, ritual, or recreational purposes and include a wide range of substances, such as caffeine, cocaine, LSD, alcohol, tobacco, codeine, and morphine. They can be legal, like prescription medications and substances such as nicotine and alcohol, or illegal, like LSD and heroin. Both legal and illegal drugs can have psychoactive effects on the brain, potentially leading to addiction.
A specific class of psychoactive drugs known as hallucinogens is known for causing profound alterations in sensory and perceptual experiences, which can include visual hallucinations or distorted body sensations and perceptions of time.