An acid has a pH <7. 7 is the pH of a neutral substance, like water, and substance with a pH >7 are considered basic or alkaline.
        
             
        
        
        
The opposite type of reaction (where energy is taken in from the surroundings of a reaction and thus the energy of the reactants is lower than that of the products) is called an endothermic reaction
        
             
        
        
        
Explanation:
Certain materials, called conductors, allow electric charge to move pretty freely through them. ... Other materials, like plastic and rubber, are called insulators because they don't allow electric charges to move through them.
 
        
             
        
        
        
Answer:
Ionic compounds have a metal and nonmetal.
Ionic compounds are made up of ions.
Explanation:
You did not provide any formulas for me to correct, but:
- ionic compounds tend to have metals and nonmetals. (EX: NaCl)You can look at the periodic table to see which elements are metals and which are not.
 - ionic compounds are made up of ions. Ions are elements that have a charge (Like 
 or  
). To have a correct ionic compound, make sure that the ions inside of it "cancel" each other out. 
        EX: Na has a +1 charge. Cl has a -1 charge. When they are paired up,      they successfully cancel each other out (become neutral) and become the ionic compound NaCl.
The chart below shows you the charge of each element. Make sure the charge of the elements in an ionic compound "cancel" each other out. 
The very last chart shows the metals and nonmetals 
Chart 1:found in https://chem.libretexts.org/Courses/Oregon_Tech_PortlandMetro_Campus/OT_-_PDX_-_Metro%3A_General_Chemistry_I/03%3A_Nuclei_Ions_and_the_Periodic_Table/3.03%3A_Predicting_Charges_of_Ions
Chart 2: found in https://sciencenotes.org/metals-metalloids-nonmetals/
 
        
             
        
        
        
Answer:
combustion is a chemical change