Chapter 1 Flashcards
What is an hypothesis ?
It’s a tentative explanation or prediction in accord with current knowledge
In chemistry we use _________ and __________ type of information.
quantitative and qualitative
What is quantitative informations ?
numerical data
What is qualitative informations ?
non-numerical observations
what is a theory ?
It’s a well-tested, unifying principle that explains a body of facts and the laws based on them
what are the goals of sciences ? (4 goals)
o prediction
o control
o understanding
o explaining
What is a state of matter ?
An easily observed property of matter that is, whether a substance is a solid, liquid or gas.
Characteristics of solid (state of matter)
-Particle are packed closely together
-Hard
-Little volume change with changes of temperature
Characteristics of liquid (state of matter)
-Particles are arranged randomly
-They are not packed
-They can move past one another
Characteristics of gas (state of matter)
-Particles are far apart
-Move extremely rapidly
-Not constrained by their neighbours
-Volume and pressure change dramatically with temperature changes
what is the energy of motion?
Kinetic energy
The kinetic energy is responsible of…….
The temperature
Kinetic energy: In the solid state the particles ….(3 answers)
- are packed closely together
- vibrate around their average position
- Very low compressibility
Kinetic energy: In the liquid state the particles ….(4 answers)
- are oriented randomly
- occupy a little more space than the solid state and they keep moving relative to one another
- still stay close to one another
- Very low compressibility
Kinetic energy: In the gaseous state the particles ….(3 answers)
- are far apart
- move fast in a linear motion until they collide with another particle when kinetic energy is exchanged and direction of motion changes
- Very high compressibility
What is a pure substance ?
- Has a set of unique by which which it can be recognized
- It cannot be separated into 2 or more different species by any physical technique at ordinary temperature
What is a mixture?
Consist of 2 or more substances that can be separated by physical technique
What is a heterogenous mixture?
Can be detected by the naked eye
What is a homogenous mixture?
-2 or more pure substance in the same phase.
-Often called solution
What is an element?
substances that are composed of only one type of atom
What is a compound?
A compound is 2 or more different element held together by chemical bonds.
What are the 2 main differences between an element and a compound?
- A compound has distinctly different characteristics from its parent element. An element is only composed of one type of atom.
- Compound has a definite percentage (%) composition (by mass) of its combining element. An element has 100% composition of his type of atom.
What is physical properties?
are properties which can be observed and measured without changing the composition of substances
Give at least 4 physical properties. The answer has 10 properties.
o colour o state of matter o melting point o boiling point o density o solubility o electric conductivity o malleability o ductility o viscosity
What is an extensive property?
depend on the amount of a substance present
ex: the amount of energy transferred as heat from burning gasoline
What is an intensive property ?
do not depend on the amount of a substance present
ex: a sample of ice will melt at 0 Celsius, no matter is it has an ice cube or an iceberg
the ratio of two extensive properties is …………
an intensive property
What is a physical change ?
- the identity of a substance is preserved
- a physical change does not result in a new chemical substance
- the particles (atoms, molecules and ions) present before and after the change are the same
What is a chemical change?
- one or more substances (reactants) are transformed into one or more different substance (products)
- the representation of the change using chemical formulas is the chemical equation
What is the type of energy associated with motion?
Kinetic energy
which type of energy results form an object’s position or state ?
potential energy
Acoustic energy is what type of energy?
Kinetic energy
Gravitational energy is what type of energy?
Potential
Chemical energy is what type of energy?
Potential
Mechanical energy is what type of energy?
Kinetic
electrical energy is what type of energy?
Kinetic
Thermal energy is what type of energy?
Kinetic
electrostactical energy is what type of energy?
Potential
nuclear energy is what type of energy?
Potential
What is the Law of conservation of energy?
Energy can neither be created nor destroyed
In a chemical reaction what is the endothermic reaction?
Sum of the bond energy in all REACTANTS +heat ABSORBED=sum of the bond energy in all PRODUCTS
In a chemical reaction what the the exothermic reaction?
Sum of the bond energy in all PRODUCTS + heat EMITTED= sum of the bond energy in all REACTANTS
