Scientific Method
What is a hypothesis?
A testable question or prediction
What type of matter contains only one kind of atom?
Element
Is density a physical or chemical property?
Physical property
Which state of matter has a definite shape and definite volume?
Solid
What phase change occurs when a solid becomes a liquid?
Melting
A student investigates whether water temperature affects how quickly sugar dissolves. What is the independent variable?
Water temperature
What type of matter is made of two or more elements chemically combined?
Compound
Is flammability a physical or chemical property?
Chemical property
Which state has a definite volume but takes the shape of its container?
Liquid
Is evaporation endothermic or exothermic?
Endothermic
A student investigates whether water temperature affects how quickly sugar dissolves. What is the dependent variable?
Dissolve time
Classify: salt water
Homogeneous mixture
Is melting ice a physical or chemical change? Explain why.
Physical change because the substance remains water.
Why can gases be compressed but solids generally cannot?
Gas particles have much more empty space between them
According to Boyle's Law, what happens to pressure when the volume of a gas decreases?
Pressure increases, assuming temperature stays constant.
Why should scientists conduct multiple trials?
To make results more reliable and reduce the effect of random error.
What is the difference between a homogeneous and heterogeneous mixture?
A homogeneous mixture is uniform throughout; a heterogeneous mixture is not uniform throughout.
Is burning wood a physical or chemical change? Explain why.
Chemical change because new substances are produced.
What happens to the particles of a substance when its temperature increases?
The particles move faster and have greater kinetic energy.
A gas has a volume of 4.0 L at a pressure of 2.0 atm. If the pressure increases to 4.0 atm, what is the new volume?
(P1 x V1 = P2 x V2)
2.0 L
A student thinks plants grow faster when given more fertilizer. Identify the independent variable, dependent variable, and one constant in an experiment testing this idea.
Classify each as an element, compound, homogeneous mixture, or heterogeneous mixture:
Gold
Water
Trail mix
Which type of change is occurring? Explain your reasoning.
A clear liquid and another clear liquid are mixed. The mixture suddenly becomes cloudy and a solid forms at the bottom.
Chemical change. The formation of a new solid (precipitate) is evidence that a new substance formed.
A sealed container of gas is heated. The volume stays constant. What happens to the pressure, and why?
Pressure increases because the faster-moving particles collide with the container walls more frequently and/or with greater force.
A gas occupies 2.0 L at 300 K. If the temperature increases to 450 K while pressure stays constant, what is the new volume?
V1 / T1 = V2 / T2
3.0 L