Units, data and chemicals Flashcards
what are qualitative and quantitative measurements
Qualitative being descriptive non numerical measurements eg colour.
Quantitative being numerical data eg temperature, height, weight.
what can quantitative data be
discrete- info with a finite number of values and cannt be divided meaningfully
based on counts/classification e.g no. of children
continuous- info that can be measured on a scale and can be divided into smaller increments. e.g- lenght, height
what can qualitative data be
nominal- categorical data that has no particular rank or order. e.g gender, ethnicity
ordinal- categorical that does have particular rank in order. e.g fitness, flexibility, status
binary- only yes/ no options
what are properties
a characteristic of a substance that can be observed
what are physical properties and chemical properties
physcial- can be observed without changing the identity of the substance. ex- luster, metal and boiling points, ductility, phase of matter(solid,liquid,gas), density, solubility, odor
chemical- can ONLY be observed by changing the identity of a substance. ec- flammability, combustibility. toxicity, ph, ability to rust, reactivity with water, air, acids etc
what are the physical properties of matter
Materials are either
pure substances -with distinct measurable properties (e.g. melting and boiling point reactivity, strength?
mixtures with properties dependent on the identity and relative amounts of the substances that make up the mixture.
what are mixtures
two or more substances combined together in such a way that each remains unchanged
Mixtures are either homogeneous or heterogeneous.
Can be physically separated.
what are homogenous and heterogenous mixtures
heter- particles distributed non uniformly ex- cereal in milk, ice in soda, soil, blood
homo- particles distributed uniformly ex- vodka, steel air, rain
what is a solution and substance
a homogeneous mixture composed of two or more substances.
Substances are the solute (what goes in the solvent) and the solvent (thing that does the dissolving)
what is an unsaturated solution
A chemical solution that can have more solute added to it which will dissolve (until it reaches the maximum saturation point)
what is a saturated solution
A chemicalsolutioncontaining the maximum concentration of a solute dissolved in the solvent.
Additional solute will not dissolve in asaturated solution
elements and compounds:
Occur naturally, same composition throughout the substance and everywhere in the world. Atoms of different elements combine in fixed ratios to form compounds
what are elements
The simplest form of matter.
Cannot be broken down or separated into a simpler substance.
Building blocks for all other substances.
what are compounds
Chemical combination of 2 or more different atoms/elements/substances in fixed ratios.
Cannot be physically separated.
Have properties different than the elements that are combined.
list chemical and physical changes
physical changes- Do not create or break molecules Changes can be reversed Examples of physical changes: - the phase changes - a solid dissolves - a dissolved substance crystalizes - an object is broken or re-shaped chemical-New products formed Involves creating or breaking molecules Not easily reversible Signs of a chemical change; - the substance changes colour - heat is released - a new type of gas is produced - a new type of solid is produced
what is precision and accuracy
Accuracy reflects the closeness of a measured value to a true or accepted value.
Precision describes the agreement between two or more measurements made in the same way( i.e. replicates).
what are the types of errors
0 error -when the pointer or the end of the ruler is not on the zero to begin with.
Calibration error-, for example a stopwatch that runs fast or slow, a thermometer badly graduated, or a meal ruler that has expanded in the heat.
Parallax error=, for example reading a clock at an angle so that the hand appears to be over another number, reading a thermostat at an angle.
Reaction time,- for example the delay in starting a stopwatch.
What are the two main types of errors
Random errors are due to variation in the performance of the instrument and the operator. Handled by data processing e.g. taking average.
Systematic error causes a random set of measurements to be spread about a value rather than being spread about the accepted value.
finding uncertainty value
When given a set of data and be asked to determine the absolute uncertainty from the data.
To find the absolute uncertainty, take the largest value minus the smallest value and divide by 2.
what are the types of graphs
bar graphs/column graphs- used to compare facts, visualize, provides visual display for quantities and relationships
scatter plots: can show relationship between 2 variables, appropriate for qualitative data and can show how strong/weak the plotted points are
line graphs- allows to see overall trends such as increase/decrease in data value over time
box and whisker plots-
shows distribution of data, where the middle half of data is and where mid point is
pie graph- useful for showing proportions in whole data set
stem and leaf plot- shows shape of data set
list the different phase changes and states of matter involves(e.g melting: solid-liquid)
Freezing: liquid to a solid.
Melting: solid to the liquid.
Condensation: gas to a liquid.
Vaporization: liquid to a gas.
Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase.
Deposition: the substance changes directly from a gas to a solid without going through the liquid phase.
