Joel claims that “Bright White Toothpaste” removes tooth enamel stains better than all other brands. Which of the following should be documented as evidence to support his claim? 1. The amount of toothpaste used
2. The shade of teeth before and after brushing
3. The type of toothbrush used to brush teeth
4. The size of tooth

Elements and compounds are pure substances that cannot be broken down physically into a simpler substance. a physical change doesn’t break the bonds between atoms of a substance or form new ones. compounds can be broken down by a chemical change. a chemical change breaks chemical bonds and/or forms new ones between atoms of a substance. what simple substance would a compound break into? the basic elements that make it up! for example, if you passed a very strong electric current through water you’d break the chemical bonds in water and be left with oxygen and hydrogen. which of the following is an example of a chemical change? a separating water into different glasses b breaking frozen ice cubes with a hammer c running an electric current through water d boiling water to evaporate it on a stove

About __ of the mass of the cell is water

Construct at least two possible hypotheses for the student’s experiment.