Which type of matter is composed of two or more elements that are chemically combined in a fixed proportion?
(1) solution
(2) compound
(3) homogeneous mixture
(4) heterogeneous mixture

Which real-world scenarios below represent physical and chemical changes? -running a car -exploding fireworks -mixing water and powdered drink mix -combining oil and vinegar to make salad dressing -taking aspirin for a headache -diluting bleach with water-digesting dinner-spreading peanut butter on bread

A100-watt light bulb radiates energy at a rate of 100 j/s. (the watt, a unit of power or energy over time, is defined as 1 j/s.) if all of the light emitted has a wavelength of 525 nm , how many photons are emitted per second?

Citric acid has a ph between 1 and 3.  it is considered to be aa. weak acidb. weak basec. strong based. strong acid