What is the law of conservation of mass?

• Mass can be created in chemical reactions.

• Mass is conserved in chemical reactions; it cannot be created or destroyed.

• Mass is only conserved in physical changes.

• Mass can be destroyed during a reaction.

Define a chemical reaction and provide an example.

• Dissolving salt in water: NaCl -> Na+ + Cl-

• Rusting of iron: 4 Fe + 3 O2 -> 2 Fe2O3

• Photosynthesis: 6 CO2 + 6 H2O -> C6H12O6 + 6 O2

• An example of a chemical reaction is the combustion of methane: CH4 + 2 O2 -> CO2 + 2 H2O.

What are the signs that a chemical reaction has occurred?

• No visible changes in the mixture

• Change in the state of matter without heat

• Signs of a chemical reaction include gas formation, color change, temperature change, precipitate formation, and odor change.

• Formation of a solid without a reaction

Explain the difference between exothermic and endothermic reactions.

• Both exothermic and endothermic reactions release energy.

• Exothermic reactions occur only in gases; endothermic reactions occur only in liquids.

• Exothermic reactions absorb energy; endothermic reactions release energy.

• Exothermic reactions release energy; endothermic reactions absorb energy.

What is pH, and how is it measured?

• pH indicates the concentration of oxygen in water, measured with oxygen meters.

• pH is a measure of temperature, measured with thermometers.

• pH is a measure of pressure, measured with barometers.

• pH is a measure of acidity/alkalinity, measured with pH meters or indicator strips.

Describe the properties of acids and bases.

• Bases donate protons and have a sour taste.

• Acids and bases are both neutral and tasteless.

• Acids donate protons and have a sour taste; bases accept protons and have a bitter taste.

• Acids are slippery and have a sweet taste.

What is the neutralization reaction? Give an example.

• An example of a neutralization reaction is the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), which produces water (H2O) and sodium chloride (NaCl).

• The reaction between hydrogen peroxide and baking soda.

• The reaction between potassium chloride and water.

• The reaction between vinegar and oil.

How do you identify a strong acid versus a weak acid?

• Strong acids are always more concentrated than weak acids.

• Strong acids do not conduct electricity in solution.

• Strong acids fully dissociate in water; weak acids partially dissociate.

• Weak acids have a higher pH than strong acids.

What role do catalysts play in chemical reactions?

• Catalysts are consumed in the reaction and do not affect the outcome.

• Catalysts change the products of the reaction to create new substances.

• Catalysts slow down chemical reactions by increasing activation energy.

• Catalysts speed up chemical reactions by lowering activation energy.

Explain the concept of molarity in relation to acids and bases.

• Molarity measures the volume of a solution in milliliters.

• Molarity is the temperature of a solution affecting acid strength.

• Molarity is the concentration of a solution expressed as moles of solute per liter of solution, crucial for understanding the behavior of acids and bases.

• Molarity is the weight of solute in grams per liter of solution.