In a laboratory, Selima added five drops of hydrochloric acid to a container with sodium bicarbonate. Which observation helps her determine whether a chemical change has taken place?

What is driving behind plate tectonics (plate movment)? a) gravity only b) inertia c) convection and gravity d) the sun theres no option for science so i picked chemistry. plz

Margaret wants to make an orange flavored drink by stirring powdered drink mix into a glass of water. she doesn't like drinks that have small clumps of powdered solid in them, so she wants the drink to be a perfect solution. what factors should margaret not consider when deciding how much powder to add to her glass of water?

What mass of natural gas (ch4) must you burn to emit 276 kj of heat?