Units, data and chemicals

Question 1

what are qualitative and quantitative measurements

Answer 1

Qualitative being descriptive non numerical measurements eg colour.
Quantitative being numerical data eg temperature, height, weight.

Question 2

what can quantitative data be

Answer 2

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

Question 3

what can qualitative data be

Answer 3

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

Question 4

what are properties

Answer 4

a characteristic of a substance that can be observed

Question 5

what are physical properties and chemical properties

Answer 5

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

Question 6

what are the physical properties of matter

Answer 6

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.

Question 7

what are mixtures

Answer 7

two or more substances combined together in such a way that each remains unchanged
Mixtures are either homogeneous or heterogeneous.
Can be physically separated.

Question 8

what are homogenous and heterogenous mixtures

Answer 8

heter- particles distributed non uniformly ex- cereal in milk, ice in soda, soil, blood
homo- particles distributed uniformly ex- vodka, steel air, rain

Question 9

what is a solution and substance

Answer 9

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)

Question 10

what is an unsaturated solution

Answer 10

A chemical solution that can have more solute added to it which will dissolve (until it reaches the maximum saturation point)

Question 11

what is a saturated solution

Answer 11

A chemicalsolutioncontaining the maximum concentration of a solute dissolved in the solvent.
Additional solute will not dissolve in asaturated solution

Question 12

elements and compounds:

Answer 12

Occur naturally, same composition throughout the substance and everywhere in the world. Atoms of different elements combine in fixed ratios to form compounds

Question 13

what are elements

Answer 13

The simplest form of matter.
Cannot be broken down or separated into a simpler substance.
Building blocks for all other substances.

Question 14

what are compounds

Answer 14

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.

Question 15

list chemical and physical changes

Answer 15

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

Question 16

what is precision and accuracy

Answer 16

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).

Question 17

what are the types of errors

Answer 17

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.

Question 18

What are the two main types of errors

Answer 18

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.

Question 19

finding uncertainty value

Answer 19

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.

Question 20

what are the types of graphs

Answer 20

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

Question 21

list the different phase changes and states of matter involves(e.g melting: solid-liquid)

Answer 21

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.