Chemical reactions - quiz 2 Flashcards
(38 cards)
What are exothermic reactions?
Exothermic reactions release energy in the form of heat to its surroundings. The total chemical energy of the products is LESS than the total chemical energy of the reactants
What are endothermic reactions?
Endothermic reactions absorb heat, making their surroundings colder. The total chemical energy of the products is MORE than the total chemical energy of the reactants.
Examples of endothermic reactions?
Photosynthesis, when you eat sherbet
Examples of exothermic reactions?
Combustion
Predict the products of acid + metal
acid + metal → hydrogen gas + salt
Predict the products of acid + base
acid + base (neutralisation) → water + salt
Predict the products of acid + carbonate
acid + carbonate → carbon dioxide + water + salt
- Explain chemical reactions in terms of breaking bonds in reactant, rearranging atoms and forming new bonds in products *
Bonds between atoms in reactants are broken. Atoms are then rearranged. Bonds between atoms in products are formed.
Observations of chemical reactions
1) Permanent colour change
2) Gas bubble appear
3) Formation of a precipitate
4) Temperature change
5) Production of an odour
Define chemical reaction
The transformation of chemical substances into a new chemical substances by the making and breaking of bonds between different atoms.
Define reactants
A reactant is a substance that is present at the start of a chemical reaction. Substances that take part in the beginning of a chemical reaction.
Define products
A product is a substance that is present at the end of a chemical reaction.
Define chemical bond
A chemical bond is force that holds atoms or ions together as a unit. The lasting attraction between atoms and ions that enables formation of chemical compounds.
What is an ionic bond?
An ionic bond is a force that holds cations and anions together which is formed when electrons are transferred from one atom to the other
What is a pH scale?
pH means the “Power of hydrogen”. The scale varies with the concentration of hydrogen ions in a solution.
What is a pH scale used for?
pH scales are used to measure the acidity and basicity of a solution.
Which solutions are acid?
Solutions with a pH scale of less than 7 (sulfuric acid, lemon juice, vinegar)
Which solutions are bases?
Solutions with a pH scale of more than 7 (toothpaste, ammonia)
What is a neutral solution?
A solution with a pH scale of 7 (pure water, blood)
What is an indicator and how can we use it?
An indicator is a substance that changes colour in the presence of an acid or a base. Universal indicator, litmus paper.
Properties of an acid
1) sour
2) less than 7 pH
3) dissolve in water to produce hydrogen ions
e. g. HCl, H2SO4, lemon juice, vinegar
Properties of a base
1) bitter
2) more than 7 pH
3) dissolve in water to produce hydroxide ions
e. g. NaOH, Milk of magnesia (magnesium hydroxide) Mg(OH)2, shampoo, ammonia
Name for HCl
Hydrochloric acid
Formula for Hydrochloric acid
HCl
