Conservation of Mass Flashcards
(29 cards)
What is mass?
Mass is a physical quantity that must be conserved during any chemical reaction.
Why is the total mass of all the reactants in a chemical reaction the same as the mass of the products formed?
This is because atoms can be neither created or destroyed.
Give an example of a chemical reaction with an increase in mass?
When magnesium ribbon is burned in the air, the mass of the product seems to have increased.
The increase in mass is due to the magnesium ribbon combing in with oxygen in the air. Therefore, the change in mass is due to oxygen reacting with the metal.
2Mg + O2 —-> 2MgO
Why would there be a decrease in the mass of a product after a reaction?
This is due to one of the products being a gas, and the gas escapes.
Give an example of when there’s a decrease of mass in a chemical reaction.
Thermal Decomposition:
When calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide gas.
Carbon Dioxide gas escapes from the reaction into the atmosphere.
What do all chemical reactions involve?
Some form of HEAT.
Why do all chemical reactions involve heat?
Because bonds are broken and new bonds are formed.
What is endothermic?
Bond-breaking is endothermic.
This means to break bonds, you have to provide energy.
What is exothermic?
Bond-making is exothermic.
This means energy is given out when new bonds are formed.
What are examples of exothermic reactions?
Combustion; Oxidation; Neutralization reaction; Respiration.
What are examples of endothermic reactions?
Thermal decomposition;
Photosynthesis.
When do elements form new bonds?
During a chemical reaction.
When does an ionic bond happen?
When a metal reacts with a non-metal.
When is a covalent bond formed?
When 2 non-metals react.
When is a metallic bond formed?
When 2 metals react.
What do all bondings involve?
Electrons.
What does the property of a compound depend on?
The type of bonding present in the compound.
What is ionic bonding?
A type of bonding that involves the strong force of electrostatic attraction between oppositely-charged ions.
Why do metals form positively charged ions?
Metals have the tendency to lose its outer valence electrons; therefore, they form positively-charged ions.
Why do non-metals form negatively charged ions?
Non-metals have the tendency to gain electrons to complete their outer shell; therefore, they form negatively charged ions.
How do ionic compounds form?
When positive and negative ions interact, they form an ionic compound.
What is covalent bonding?
When 2 or more non-metals come together to form a bond, they mutually share electrons between them.
What can covalent compounds be classified as?
Simple molecular or Giant molecular.
Describe simple molecular compounds:
-have weak inter-molecular forces
-some of these bonds are so weak that these molecules exist as a gas at room temperature.
