Chemical reactions

In a chemical equation, is it true that -

• the reactant side and product side can have different numbers of atoms for each element
• there can be different elements on the reactant side and the product side
• an element or compound must be accompanied by a phase change
• the coefficients indicate the number of molecules of each reactant used and the number of molecules of each product made

Which of the following models best demonstrates a balanced chemical equation?

• F
• G
• H
• J

Which of the following equations demonstrates an actual chemical reaction that forms a new substance?

• A
• B
• C
• D

Which of these formulas contain equal numbers of nitrogen atoms?

• Formulas I and III
• Formulas I and IV
• Formulas II and III
• Formulas I, II, and V

The reactants are on the left side of the chemical equation.

• True
• False

In which of these compounds are there twice as many oxygen atoms as hydrogen atoms?

• H₃PO₄
• H₂SO₄
• HCIO₃
• H₂0

When a scientist mixed two chemicals, an exothermic reaction takes place. Which of the following would be proof that the reaction was exothermic?

• a change of color
• a change of state
• a temperature decrease
• a temperature increase

What types of reactions absorb and release heat?

• acidic and basic
• endothermic and exothermic
• endothermic and heat transfusion
• covalent and ionic

In the reaction methane + oxygen turns into carbon dioxide + water, the methane and oxygen are called _______________.

• reactants
• products
• neutrals
• energizers

If you combine two substances in a beaker at room temperature and the beaker feels cold to the touch, it means that the substances:

• have not reacted with each other
• have undergone an endothermic reaction
• have undergone a physical change
• have undergone an exothermic reaction