UNIT 1 Meassure Lab safety rules

NORMAS BÁSICAS DE LABORATORIO Un laboratorio puede ser un sitio peligroso, por eso es necesario cumplir una serie de normas básicas. 1. Normas de trabajo : 1.1. Conocimientos previos del fenómeno que se quiere estudiar y de algunas técnicas experimentales. 1.2. Paciencia. Hay que ser meticuloso, reposado y atento, anotando todos los detalles de la operación y razonando lo que sea necesario. 1.3. Objetividad. No nos debemos dejar influir por los demás ni por resultados preconcebidos. 1.4. Limpieza y orden . El material y el lugar de trabajo tienen que estar limpios, debiéndose dejar todo limpio y recogido al acabar el trabajo . 1.5. Buena planificación del trabajo, para aprovechar bien el tiempo. 1.6. Hay que cuidar el material utilizado, guardando el material que no se vaya a usar. 2. Advertencias generales: 2.1. No comer ni beber en un laboratorio, podemos intoxicarnos o envenenarnos. 2.2. No tocar ningún producto químico con las manos ni con la boca. 2.3. Los sólidos se manipulan con espátulas , y para trasvasar líquidos se usará una varilla de agitación,.. 2.4. El vidrio es muy frágil, se debe evitar golpearlo y cambiarlo bruscamente de temperatura. Cuidado: El vidrio frío tiene el mismo aspecto que el caliente debemos procurar no quemarnos. 2.5. Nunca se debe poner el rostro encima de ningún recipiente, para evitar salpicaduras. Si fuera necesario percibir olores solo se agita el aire con la mano. 2.6. No dejar objetos calientes encima de la mesa. 2.7. No calentar directamente los líquidos inflamables ( riesgo de explosión), sino con baño María u otro procedimiento. 2.8. Cuando se diluyan ácidos , éstos deben agregarse lentamente al agua , pero NO a la inversa.

2.9. Cuando se use un termómetro hay que asegurarse que su temperatura máxima es superior a la que se va a medir. Cuando se sumerja en un líquido nunca deberá tocar el fondo o las paredes del recipiente.

3. Medidas de seguridad: 3.1. En caso de heridas, hay que usar un desinfectante y luego cubrir con algodón y esparadrapo. Las salpicaduras en los ojos se deben aclarar con agua abundante y acudir a un médico. 3.2. Intoxicaciones. Se debe ventilar el local cuando se trabaje con sustancias volátiles. En caso de ingestión no intentar vomitar. Con los ácidos se debe ingerir agua y leche y con los álcalis hay que tomar zumo de limón o naranja (ácido cítrico ). 3.3. Incendios . No deben colocarse próximos al fuego sustancias inflamables (pelo, papel, madera, alcohol, etc...). El mechero se deberá apagar cuando no se use. 4. El cuaderno de laboratorio. La metodología del trabajo científico impone la necesidad de un cuaderno con las siguientes características. 4.1. Título de la investigación. 4.2. Introducción. En ella se situará el problema haciendo referencia a los aspectos teóricos del problema, necesarios para la emisión de hipótesis. Se indicará la bibliografía utilizada y se planteará el diseño del experimento y la concreción del procedimiento. 4.3. Contenido: Deben describirse los pasos los pasos que se han seguido durante la experimentación, el material empleado, el procedimiento utilizado para realizar las medidas, los cálculos, tablas de resultados , dificultades , etc... 4.4.Conclusiones: Deben indicarse de forma clara el resultado al que se llega y las nuevas posibilidades de investigación que surgen del trabajo, explicando si se han verificado o no las hipótesis iniciales y por qué. 5. Señales de prevención de riesgos Estas son las principales señales de riesgo :

6. Material de laboratorio. Laboratory equipment INSTRUMENT Nombre (SP) Name(UK)

Description

Regla

Ruler

A tool used to measure length

Termómetro

Thermometer A tool used to measure temperature

Balanza

Balance

A tool used to measure mass

Vaso de Beaker precipitados

A type of container used to measure the approximate volume of a liquid or mix substances

Matraz erlenmeyer

A type of container used to measure the approximate volume of a liquid or mix substances. It differs from the beaker its tapered body and narrow neck.

Erlenmeyer flask

Matraz aforado Volumetric or A type of container calibrated to graduated measure a precise volume at a flask particular temperature.

Probeta

Graduated cylinder

Tubo de ensayo Test tube

A type of container used to measure the volume of a liquid.

Test tubes are used to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays.

INSTRUMENT

Nombre (SP)

Name(UK)

Description

Pipeta

Pipette pipet

or A type of container used to measure the volume of a liquid.

Bureta

Burette buret

or A tool used for dispensing of variable, measured amounts of liquids

LINK Descripción de material de laboratorio

UNIT 1. MEASURE 1. CHEMICAL AND PHYSICAL CHANGES. We can see that all things are continuously changing. There are two types of changes in the environment: chemical and physical. CLINK ON PICTURE (easy)

CLINK ON PICTURE (difficult)

a) Physical changes: They are those changes that DO NOT produce a new substance. If you break a bottle, you still have glass. Some common examples of physical changes are; breaking, crushing, cutting , bending and changes in state, such as melting, freezing, condensing, etc....

b) Chemical changes: They are changes that result in the production of another substance. If you burn a paper , you are carrying out a chemical reaction that releases carbon. Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, oxidation, burning and decomposition. 2. IDENTIFICATION OF SUBSTANCES. CHARACTERISTICS PROPERTIES. Characteristic properties serve to identify and classify substances. They don't depend on the amount of substance. Characteristic properties would be : Colour Hardness ( dureza) It is the resistance of a substance to be scratched (rayado). It can be hard ( difficult to be scratched.) or soft (easy to be scratched) Density . It indicates how tightly packed the substances are. It is calculated by dividing the mass by the volume. Freezing/melting point and boiling/condensing point are the temperatures at which the matter change state. For example the melting point of water is 0 ºC. Solubility . It is the ability of a substance to dissolve . The substance which is being dissolved is called the solute ( soluto ) and the substance in which the solute is dissolved into is called the solvent ( disolvente). Non-characteristic properties ( propiedades generales) serve to measure the substances, but NOT to identify them . They would be the weight (peso), length (longitud), etc . Matter : Anything that has mass and and takes space

3. UNITS A magnitude is a body's property that can be measured and it is used to study and describe them. The International System of Units is the modern form of the metric system. It is necessary to translate all the units into International System of Units (SI) to do the calculations. Quantity Unit Unit Symbol Length

metre

m

Mass

kilogram

Kg

Time

second

s

Speed

m/s

Energy

Joule

J

The main SI prefixes used to form decimal multiples and submultiples of SI units are: Symbol Name Factor

Symbol Name Factor

P

peta

1015

d

deci

10 -1

T

tera

1012

c

centi

10 -2

G

giga

109

m

mili

10 -3

M

mega 106

μ

micro 10 -6

k

kilo

103

n

nano

10 -9

h

hecto 102

p

pico

10 -12

da

deca

101

f

femto 10 -15

4. CONVERSION FACTORS. A conversion factor is used to convert a measured quantity to a different unit of measure .A conversion factor is a number by which a quantity that is expressed in one set of units must be multiplied in order to convert it into another set of units . A conversion factor is made from any equality. Like 100 cm = 1 m, or 60 min = 1 hour. Each can be written as a fraction, or ratio of two quantities. Either quantity can be in the numerator or denominator. We determine the actual ratio so that the units that we don´t want will cancel out, leaving the units that we do want. You can gang up as many conversion factors in a row as is necessary to convert. Example: 5. MISTAKES There are two types of mistakes: a) Absolute mistake: It is the amount of error in a measurement. It has unit. E a= | E true – Emeasured | b) Relative mistake: It gives an indication of how good a measurement is. It has no unit. It is used to know if the measurement is good or bad. It is between 0 and 1.

6. MEASUREMENT Which of the following central circles is bigger? Measure them and check it.

Are the following lines parallel?

Indicate which of the following lines is longer A B

Conclusion: Do not trust your senses, they can deceive, it is necessary to measure to obtain the true value. 7. SCIENTIFIC METHOD The scientific method is the process by which scientists, collectively and over time, endeavor (tratan, intentan) to construct an accurate (that is, reliable, consistent and non-arbitrary) representation of the world. The scientific method has four steps: a) Observation and description of a phenomenon or group of phenomena. b) Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation. c) Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations. d) Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments. If the experiments bear out (confirman) the hypothesis it may come to be regarded as a theory or law of nature . If the experiments do not bear out the hypothesis, it must be rejected or modified.

8. INSTRUMENTS They are used to measure the matter properties. They can be rulers, scales, chronometers, thermometers, test tubes, etc... The sensibility of an instrument is the smallest amount of property that it can measure. The International System of Units (SI) is a system of units and it is the world's most widely used. Activity 1 . Fill in the following table: INSTRUMENT

Nombre (SP)

Name(UK)

Measures

SI Unit

Sensibility

m

Ruler

Length

m

Calibre o

m

Pie de rey

Balanza

Kg

Kg

s

Probeta m3

ºC

0,1 mm

9. Material de laboratorio. Laboratory equipment INSTRUMENT Nombre (SP) Name(UK)

Description

Regla

Ruler

A tool used to measure length

Termómetro

Thermometer

A tool used to measure temperature

Balanza

Balance

A tool used to measure mass

Vaso precipitados

de Beaker

A type of container used to measure the approximate volume of a liquid or mix substances

Matraz erlenmeyer

Erlenmeyer flask

A type of container used to measure the approximate volume of a liquid or mix substances. It differs from the beaker its tapered body and narrow neck.

Matraz aforado

Volumetric or A type of container calibrated to graduated measure a precise volume at a flask particular temperature.

Probeta

Graduated cylinder

A type of container used to measure the volume of a liquid.

Tubo de ensayo

Test tube

Test tubes are used to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays.

INSTRUMENT

Nombre (SP)

Name(UK)

Description

Pipeta

Pipette pipet

or A type of container used to measure the volume of a liquid.

Bureta

Burette buret

or A tool used for dispensing of variable, measured amounts of liquids

LINK Descripción de material de laboratorio

STUDENT BOOK http://www.iesnicolascopernico.org/FQ/3ESO/tema1.pdf LINKS: 1) http://www.vrml.k12.la.us/3rd/homework/science/un1/science3un1.htm 2) http://teacher.nsrl.rochester.edu/phy_labs/appendixe/appendixe.html 3) http://www.unc.edu/~rowlett/units/sipm.html 4) http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=guide_tables_prefix 5) http://www.sky-web.net/science/balancing_chemical_equations_examples.htm 6) http://chemistry.about.com/od/lecturenotesl3/a/chemphyschanges.htm 7) http://www.chem4kids.com/files/matter_chemphys.html 8) http://www.virted.org/chemist/pcchange.html 9) http://www.lcc.ukf.net/KS3Chem/chemphychanges.htm#ce 10) http://www.ausetute.com.au/chemphys.html 11) http://www.bbc.co.uk/schools/ks3bitesize/science/chemical_material_behaviour/ 12) http://answers.yahoo.com/question/index?qid=20080909034618AAM1FAv 13) http://www.iesnicolascopernico.org/FQ/3ESO/tema1.pdf 14) http://preparatorychemistry.com/Bishop_Study_Guide_8.pdf CAMBIO DE UNIDADES 3º DE ESO MAGNITUD

UNIDAD S.I.

RECUERDA

LONGITUD

m

( metro)

1 Km = 1000 m

MASA

kg

( kilogramo)

1 Kg = 1000 g

VOLUMEN

m3

( metro cúbico)

1 m3 = 1000 L

TIEMPO

s

( segundo )

1 min = 60 s

SUPERFICIE

m

2

1 L = 1000 mL

1 L = dm3

1cm3 = 1 mL

(metro cuadrado)

1) MASA Cambiar a gramos las siguientes cantidades 2

Kg

=

0,245 Kg =

Cambiar a kilogramos las siguientes cantidades g 250 g

=

Kg

=

Kg

23,5 Dg =

g 25 . 10 mg =

Kg

230

g 42

Kg

mg

g 230 Mg

=

7

Hg=

2) LONGITUD. Cambiar a metros las siguientes cantidades 250

cm =

45,67 Km =

Cambiar a centímetros las siguientes cantidades m 2,14 m =

cm

m 600 m =

cm

3) VOLUMEN Cambiar a m3 las siguientes cantidades

Cambiar a litros las siguientes cantidades 3

2500

L=

m 2,5 m3

=

L

6,5

Km =

m3 4000 cm3 =

L

3

3

670

dm =

3

m 4000 mL = 3

L

234.10 cm =

m 3,5 KL

=

L

2000

m3 58 dm3

=

L

=

L

4

50

3

HL= KL=

3

m 100 dm

3

4) TIEMPO Cambiar a segundos las siguientes cantidades 24 horas

Cambiar a horas las siguientes cantidades

=

s 2,5 días

=

horas

2,5 minutos =

s 3,5 meses =

horas

2 horas 50 minutos

s 45 minutos =

horas

5) Cambiar a unidades del Sistema Internacional ( S.I.). CANTIDAD

S.I.

CANTIDAD

6,25 s (segundos)

600 cm3

25. 104 mg

5678 mg

4500 m

50 minutos

850 KL

600 mL

2 días

44 MKg

4000 L

23 Tm

S.I.

PROBLEMAS FACTORES DE CONVERSIÓN 1) Numerosas evidencias científicas han puesto de manifiesto que en 18 g de agua hay un total de 6,02·1023 moléculas de agua. ¿Qué cantidad de moléculas habría en un vaso de agua de 120 gramos? ¿Cuánto pesarían 4,25·1022 moléculas de agua? ( SOL : 4,01.1023 moléculas; 1,27 g ) 2) Una docena de naranjas pesa 1520 gramos y cuestan 1,74 euros. ¿Cuántas naranjas podríamos comprar con 10 euros? ¿Cuánto pesarían esas naranjas? Si un ciudadano suizo compra en el mercado 5 kilogramos de naranjas, ¿Cuánto le costarían? Si decide pagar en su moneda (el franco suizo) ¿cuánto habrá de pagar si se sabe que 1 euro = 1,59 franco suizo? ( SOL : 68,87 naranjas; 8,74 kg ; 9,99 € ; 15,88 francos ) 3) Un autobús es capaz de circular constantemente a 72 km/h. ¿Durante cuánto tiempo deberá estar en circulación para recorrer una distancia de 490 km? ¿Qué distancia habría recorrido en 20 minutos? ( SOL : 6,8 h; 24 min) 4) Una habitación mide 4,5 m de larga, 3,2 m de ancha y 2,9 m de alta. ¿Qué masa de aire habrá en su interior, si se sabe que en esas condiciones 1 mL de aire pesa 1,31 g? ( SOL : 54705,6 Kg ) 5) Un depósito contiene 0,18 m3 de cierto líquido. Posee un pequeño orificio en su base de tal modo que gotea a un ritmo medio constante de 210 gotas por minuto. Sabemos que 2 mL de líquido son 31 gotas. ¿Qué tiempo tardará el depósito en quedarse a la mitad? ( SOL : 6642,85 min ) 6) Un colegio posee un total de 410 alumnos. Sabemos que de cada 20 alumnos, 8 usan gafas. Igualmente sabemos que de cada 4 alumnos que usan gafas, 3 son niños. ¿Cuántos alumnos hay que usan gafas en el colegio? ¿Cuántos de éstos son niños? (SOL : 164 alumnos con gafas; 123 niños con gafas ) 7) Una fábrica es capaz de envasar y precintar 1425 sardinas en 95 latas, empleando en ello 48 minutos de tiempo. Cada lata de sardina envasada se vende posteriormente a 1,7 euros. En cierta ocasión recibió un lote de 6195 sardinas. ¿Cuántas latas hicieron falta? Si se empezó el proceso a las 11:00 h de la mañana, ¿a qué hora se terminó? ¿A cómo se vendieron finalmente? (SOL : 413 latas; 208,67 min ; 702,1 € )

8) Cierto recóndito país tiene un total de 52 millones de habitantes, de los que el 39 % son personas mayores de 55 años. El 18 % de las personas mayores de 55 años ya está jubilada, y el 40 % de las personas jubiladas cuida frecuentemente a sus nietos. ¿Cuántas son las personas que cuidan a sus nietos? ¿Cuántas personas mayores de 55 años NO están jubiladas? ( SOL : 1.460.160 personas cuidan a sus nietos; 16.629.600 personas ) 9) Una oferta de refrescos consiste en la venta de un paquete que contiene 8 botellas de 250 mL cada una al precio de 2,5 euros. En cada paquete, 4 botellas son de refresco de limón, 2 botellas son de refresco de cola y las otras 2 botellas son de naranja. ¿Cuántos paquetes de refrescos podríamos comprar con 50 euros? ¿Cuántos litros de refresco de limón, cola y naranja tendríamos? ¿Cuántas botellas en total tendríamos finalmente para reciclar? ( SOL : 20 paquetes; 20 L de limón; 10 L de cola; 10 L de naranja; 160 botellas ) 10) En cierto establecimiento que posee conexión wifi, nos cobran 1,45 euros por cada 80 minutos de conexión. Un turista americano de visita por España, permanece conectado 2 horas y 20 minutos. A la hora de hacer el pago, lo hace con su tarjeta de crédito, efectuándose el cobro en dólares. Sabemos que 1 euro = 1,374 dólares. a) ¿Cuántos dólares le facturaron a esta persona americana? b) ¿Qué tiempo podría estar conectado con 15 dólares? (SOL : 3,49 $ ; 601,72 min ) 11) Un depósito contiene 40 m3 de aceite, y tiene adosado un grifo que es capaz de suministrarnos 70 L de aceite por minuto. a) Para cierta operación, precisamos sacar 600 L de aceite. ¿Cuánto tiempo necesitamos tener abierto el grifo? b) Sabemos que 1 L del aceite pesa 900 g. ¿Cuánto pesa el aceite que quedó en el depósito? ( SOL : 8,57 min ; 35.460 kg ) 12) Un avión es capaz de moverse a 1250 km/h. a) ¿Qué distancia es capaz de recorrer en 10 minutos? b) La velocidad del sonido en el aire es de 340 m/s. A esa cantidad se la denomina “match”. Expresa la velocidad del vehículo en match. ( SOL : 208,33 km; 1,02 match ) 13) Una caja de aspirinas contiene 20 comprimidos, de 500 mg cada uno. En la farmacia cada caja nos cuesta 0,85 euros. a) Cierto enfermo ha de tomar diariamente 1,68 g de aspirina (ac. acetil salicílico). ¿Cuántos comprimidos deberá tomar? b) ¿Cuántos gramos de aspirina ingiere al cabo de una semana? c) ¿Cuánto dinero gasta en aspirinas esta persona al cabo de un mes? d) ¿Cuántos comprimidos (aproximadamente) podríamos comprar con 20 euros? ¿Cuántas cajas? ( SOL : 3,36 comprimidos; 11,76 g; 4 euros; 470,6 comprimidos; 23,53 cajas ) 14) Tenemos en casa un grifo estropeado, de tal modo que gotea a un ritmo constante de 58 gotas por minuto. Sabemos que 10 gotas son 1 mL de agua, y que 1 m3 de agua cuesta 1,98 euros. a) Si el grifo ha estado goteando ininterrumpidamente durante los dos meses que hemos estado fuera de vacaciones, ¿qué cantidad agua se ha desperdiciado? b) ¿Cuál ha sido el coste del agua desperdiciada? ( SOL : 501,12 L; 1 € )

15) Expresa en unidades del S.I.: a) 340 cm3 b) 0,4 km c) 500μg d) 120 km/h e) 2 g/mL f) 5,7 km/min g) 6 g.cm/s2

( SOL : 3,4.10-4 m3 ) ( SOL : 400 m ) ( SOL : 5.10 -7 m ) ( SOL : 33,33 m/s) ( SOL : 2000 kg/m3 ) ( SOL : 95 m/s ) ( SOL : 6.10-5 kg.m/s2 )

h) 0,32 g/cm3 i) 108 Km/h j) 54 cm3/h k) 6 dam/min l) 3,5 g/L m) 4 dg/cm3 n) 3 L/h

( SOL : 320 kg / m3 ) ( SOL : 30 m/s) ( SOL : 1,5.10-8 m3/s) ( SOL : 1 m/s ) ( SOL : 3,5 kg/m3 ) ( SOL : 400 kg/m3 ) ( SOL : 8,33.10-7 m3/s)

CONVERSION FACTORS EXERCISES 1) The diameter of a proton is 2.10-15 meter. What is the diameter in nanometers? (Ans: 2.10 -6 nm) 2) The mass of an electron is 9.1093897.10 -31 Kg. What is this mass in nanograms? (Ans: 9.1093897.10-19 ng) 3) Convert 4.352 micrograms to megagrams. ( Ans : 4.352  10-12 Mg) 4) A piece of Styrofarm has a mass of 88.978 g and a volume of 2.9659 L. What is its density in g/ml? ( Ans : 0.030000 g/mL) 5) The density of blood plasma is 1.03 g/mL. A typical adult has about 2.5 l of blood plasma. What is the mass in kilograms of the blood plasma in this person? ( Ans : 2.6 kg ) 6) When you are doing heavy work, your muscles get about 75 to 80 % by volume of your blood. If your body contains 5.2 liters of blood, how many liters of blood are in your muscles when you are working hard enough to send them 78 % by volume of your blood ? ( Ans : 4.1 L blood to muscles ) 7) A tree trunk is found to have a mass of 1.2 10 4 kg and a volume of 2.4 10 4 L. What is the density of the tree trunk in g/ml? ( Ans : 0.50 g/mL) 8) The volume of the earth's oceans is estimated to be 1.5 10 gallons? ( There are 3.785 L/gal) ( Ans: 4.0  1020 gal )

18

kiloliters. What is this volume in

9) When you are rest, your heart pumps about 5.0 liters of blood per minute. Your brain gets about 15 % by volume of your blood. What volume of blood, in liters, is pumped through your brain in 1.0 hour of rest? ( Ans : 45 L )

10) Convert the following ordinary decimal numbers to scientific notation. a) 67,294 6.7294 10 ? b) 438,763,102 4.38763102 10 ? c) 0.000073 7.3 10 ? d) 0.0000000435 4.35 10 ? 11) Convert the following numbers expressed in scientific notation to ordinary decimal numbers. a) 4.097 10 3 4,097 b) 1.55412 104 ? -5 c) 2.34 10 ? d) 1,2 10 -8 ? 12) Complete each of the following conversion factors by filling in the blank on the top of ratio. (1000 1Km

(

m

min 1h

)

)

(

cm 1m

(

1Tbytes

)

(

cm 3

(

1L

)

bytes 1 year days

)

)

(

1g ng

(

)

1cm inches

)

13) The diameter of typical bacteria cells is 0.00032 centimeter. What is this diameter in micrometers? ( Ans : 3.2 m ) 14) A piece of balsa wood has a mass of 15.196 g and a volume of 0.1266 L. What is its density in g/mL? ( Ans: 0.1200 g/mL ) 15) The density of water at 0ºC is 0.99987 g/mL. What is the mass in kilograms of 185 mL of water? (Ans:0.1850 kg ) 16) A peanut butter sandwich provides about 1.4 10 3 KJ of energy. A typical adult uses about 95 Kcal/h of energy while sitting. If all of the energy in one peanut butter sandwich were to be burned off by sitting, how many hours would it be before this energy was used? ( A Kcal is a dietary calorie. There are 4.184 J/cal ) ( Ans : 3.5 h ) 17) When one gram of hydrogen gas, H2 (g) is burned, 141.8 kJ of heat is released. How much heat is released when 2.3456 kg of hydrogen gas is burned? ( Ans: 3.326  105 kJ ) 18) When one gram of carbon in the graphite form is burned, 32.8 KJ of heat is released. How many kilograms of graphite must be burned to release 1.456 10 4 KJ of heat? ( Ans : 0.444 kg C )

19) A typical nonobese male has about 11 kg of fat. Each gram of fat can provide the body with about 38 kJ of energy. If this person requires 8.0 10 3 kJ of energy per day to survive, how many days could he survive on his fat alone? (Ans: 52 days ) 20) During quiet breathing, a person breathes in about 6 L of air per minute. If a person breathes in an average of 6.814 L of air per minute, what volume of air in liters does this person breathe in 1 day ? ( Ans : 9812 L air ) 21) The average heart rate is 75 beats/min. How many times does the average person's heart beat in a week ? ( Ans: 7,6.10 5 beats )

UNIT 1: INTRODUCTION TO PHYSICS AND CHEMISTRY Contents 1. What are Physics and Chemistry? 2. Scientific method. 3. Magnitudes and units. 4. Conversion of units. 5. Significant figures. 6. Scientific notation. 7. Errors. 8. Properties of matter. 9. Advices to solve the exercises. 1. What are Physics and Chemistry? Science is the knowledge of things through watching and reasoning. Experimental science is the one which is based on the experience, in reality. Physics and Chemistry, and Biology and Geology too, are experimental sciences. Physics and Chemistry study phenomena, i.e. natural facts, facts which occur in the real world. Physics studies the processes in which there is not a change in composition. Chemistry studies the processes in which there is a change in composition. Example: pushing a cart is physical or chemical? Solution: physical, because there is no change of composition. Exercise: classify the following phenomena in physical or chemical: a) The falling of an apple. b) The echo. c) Evaporating water. d) Oxidation of a nail. e) Mixing bleach and ammonia. f) Mixing salt and water. 2. The scientific method Scientific research consists of doing activities to make our knowledge grow about some matter. Example: research can be done to get a high temperature resistance oil or a medicament to heal an illness. Research follows the scientific method, which has five steps: 1) Watching the phenomenon. 2) Thinking about an hypothesis. 3) Making experiments in the lab. 4) Analysing the results. 5) Presenting the conclusions. With more detail: 1) Watching the phenomenon: it must be carefully done. 2) Thinking about an hypothesis: an hypothesis is a supposition to explain a phenomenon. Example: if a stone drops on the floor, there is something which attracts it to the Earth. Exercise: if the phenomenon is that we are hotter with a dark T-shirt than with a bright one, what could be the hypothesis? 3) Making experiments in the lab: experiments are made to check which hypothesis was the correct one. The right experiments must be made and a lot of measures. The factors which make influence on the phenomenon must be found. Example: what factors make influence on the result of a soccer match ? 4) Analysing the results: measurements can be expressed in graphs: Equation y = a · x + b Example y = 3 · x + 2

y = a · x2 y = 6 · x2

y=a/x y = 10 / x

To make graphs, a table of values must be made. X values are invented, and y values are obtained from the equation. If the function is a straight line, only two points are needed. If it is a curve, at least five are needed. 5) To present the conclusions: once the hypothesis is checked, the scientific law is reached. A scientific law is a formula which has been experimentally checked. Examples: h=5t2

Falling bodies law

V=I• R

Ohm's law

A theory is a set of hypothesis and laws. Example: the theory of relativity. 3. Magnitudes and units A magnitude is anything which can be measured. Examples: length, mass, time and temperature. A unit is something taken as a reference to measure. Examples: the metre (m), the kilogramme (kg), the degree celsius (ºC). To measure is to compare a magnitude with an unit. They must not be confused. Measures can be expressed this way: (number) (unit) Examples: 2 m, 3 h, 40 ºC. There are two types of magnitudes: Fundamentals and Magnitudes Derivatives Fundamental magnitudes are those which cannot be broken up into or related with any other magnitudes. The main fundamental magnitudes are: length, mass, time and temperature. Derivative magnitudes are those which can be related with the fundamental ones. Example: surface is related with length: area = length2 . A unit system is a determined set of units. The most used one is the SI (international system of units) . Some SI units are: Type of magnitude Magnitude Unit Fundamental Length m Mass kg Time s Derivative Area m2 Volume m3 Velocity m/s Acceleration m/s2 Force N, newton Work J, joule Energy J, joule Power w, watt Density kg/m3 Pressure Pa, pascal These units can be unsuitable to measure great magnitudes or little magnitudes. Example: to measure the mass of a pencil the kilogramme is not used. In these cases, these prefixes can be used: Prefix Symbol Equivalence kilo k 103 hecto h 102 deca da 10 metre, gram ,second deci d 10-1 centi c 10-2 mili m 10-3 4. Conversion of units Units only can be converted into another units of the same magnitude. Example: km can be converted into cm, but not into mg. Conversion of linear units (those without exponent): there are two ways to do it: a) Directly: it consists of counting the steps between both units in the chart above, but without counting one of the units. Going up in the chart means to divide by 10nº of steps and going down

means to multiply by 10nº of steps. Example: convert 1 dag in mg. Solution: there are four steps between deca and mili. We are going down in the table, so: 1 dag = 1.104 = 104 mg Examples: 1 dag  mg 8 cg  kg 4 4 1 dag = 1·10 = 10 mg 8 cg = 8 105 = 8 · 10-5 kg Exercise: convert: 1) 80 km into cm

2) 4 mg into hg

3) 12 dg into dag

b) By means of conversion quotients: a conversion quotient is a quotient in which numerator is equivalent to denominator. Examples: The method consists of multiplying the initial unit by one or several conversion quotients so that all the units disappear. Example: convert 8000 cm  km Exercise: convert: 1) 72000 s into h 2) 8 min into cs 3) 50 hm/h into m/s Conversion of square units: those are the ones with an exponent 2. In this case, the number of steps must be multiplied by two. Example: convert: 20 hm2 in cm2. Conversion of volume units: there are three possibilities: a) Cubic units into cubic units. b) Litre units into litre units. c) Cubic units into litre units. a) Cubic units into cubic units: it is the same as in squared units, but now the number of steps must be multiplied by three. b) Litre units in litre units: the same as linear units, without multiplying by 2 or 3. Example: convert 67 cl into hl c) Cubic units in litre units: the best way is to use conversion quotients. Usually, it cannot be done directly but using an alternative route. The initial unit must be converted into litres (l), the litres into dm3 and the dm3 into the final unit. Bear in mind that: 1 l = 1 dm3 and 1 cm3 = 1 ml. Example: convert 700 dal in hm3. 5. Significant figures or significant digits Operating with the calculator, it usually appears a number with a lot of decimals, but all of the the decimals must not be written. In fact, the important thing is not the number of decimals but the number of significant figures (numbers). Significant digits are those which define a number and which appear in all the ways of writing that number. Example: next number has these significant figures: number 2, number 4 and number 8: 0'0000248 = 2'48  10-5 = 24'8 · 10-6 = 248 · 10-7 To know which digits are significant, there are these rules: 1) All the numbers from 1 to 9 are significant. 2) Number 0 is sometimes significant and sometimes not. 3) 0 is significant: When it is placed between two significant digits. Example: 2'304. When 0 is a decimal and it is placed at the end, on the right. Example: 4'30. 4) 0 is not significant: When it is placed on the left. Example: 0'00034. When it is on the right and it is not a decimal. Example: 75640. Exercise: guess the number of significant digits of the following numbers: 6 0'6 0'60 10'60 1060 0'000314 12000 12000'0 12000'1 6'21·107 The rule says that operating with numbers with different numbers of significant digits, the solution must have the same number of significant digits as the number which has the smallest number of significant digits. Example: calculate the volume of air inside a room of 16’40 m length, 4’5 m width and 3’27 m hight. Formula of the volume: Volume = length · width · height

5. Cifras significativas Cuando operamos con números decimales, suelen aparecer muchos decimales, pero no debemos anotarlos todos. En realidad, en un número no importan sus cifras decimales, sino sus cifras significativas. Las cifras significativas son aquellas que definen un número y que aparecen en todas las formas de escribir el número. Ejemplo: el siguiente número tiene como cifras significativas el 2, el 4 y el 8: 0´0000248 = 2´48 · 10-5 = 24´8 · 10-6 = 248 · 10-7 Para saber qué cifras son significativas, hay que tener en cuenta que: 1) Todas las cifras distintas de cero son significativas. 2) El cero es significativo a veces sí a veces no. 3) El cero es significativo: Cuando está situado entre dos cifras significativas. Ejemplo: 2'304. Cuando el cero es una cifra decimal y está en el extremo derecho. Ejemplo: 4'30. 4) El cero no es significativo: Cuando está situado a la izquierda. Ejemplo: 0'00034. Cuando está en el extremo derecho y no es cifra decimal. Ejemplo: 75640. The most usual case in our exercises is three significant figures. 6. Scientific notation It is the way of writing a number using 10 to the power of an exponent. The number must not begin with 0 and must have a decimal as a second number. Example: 6´34 · 10-8 is well written in scientific notation. Example: 63´4 · 10-9 is not well written in scientific notation. Example: 0´634 · 10-7 is not well written in scientific notation. To convert a number into scientific notation, count the number of places the comma is moved. X is the number of places. a) If you move to the left, x must be added to the exponent. b) If you move to the right, x must be taken away to the exponent. Examples: 4530000 = 4´53 · 106 0'0007281 = 7'281 · 10-4 3272'168 = 3'272168 · 10-3 Exercise: convert into scientific notation: a) 0'00002413 = b) 82'327 · 104 = c) 0'0007 · 108 = d) 36'21 · 10-5 = La aproximación de un número consiste en no escribir todos los decimales, sino un número cercano con menos decimales. Si el siguiente número al corte es mayor o igual que cinco, al anterior se le suma una unidad. Si no, se deja igual. Si la cifra a redondear es el 5 depende de si la cifra que se queda es par o impar. Si es impar, al eliminar al 5 el número acabado en impar sube 1 unidad. The approximation of a number consists of not writing all the decimals and writing the closest number. The long number has to be cut. If the last number before the cut is 5 or bigger than five, 1 must be added to the last number. Otherwise, the cut number stays the same. Ejercicio: aproxima estos números a tres cifras significativas: a) 3´24356 = b) 5´2485 = c) 68375´34 = d) 4,5= e) 5,5= 7. Errors It is the discrepancy between the exact value and an approximation. An approximation error can occur for several reasons: lack of sensibility of the measurement instrument, lack of attention, the temperature, the instrument does not work properly, etc. The average or arithmetic mean of several measurements There are two types of errors: the absolute error and the relative error.

The relative error gives us an idea of how good a measurement is. If it is under 5 %, it is acceptable; if it is under 1 %, it is good and if it is below 0'1 %, it is excellent.

1) FILL IN THE BLANKS science, disciplines, synonymous, distinguish, modern-day, force, Revolution, understanding, time, weapons, appliances, However, behaves Physics is a natural …........................... that involves the study of matter and its motion through space and …..........................., as well as all related concepts, including energy and …........................... More broadly, it is the general analysis of nature, conducted in order to understand how the universe …........................... Physics is one of the oldest academic …..........................., perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics had been considered …........................... with philosophy, chemistry, and certain branches of mathematics and biology, but during the Scientific …........................... in the 16th century, it emerged to become a unique modern science in its own right. …..........................., in some subject areas as in mathematical physics and quantum chemistry, the boundaries of physics remain difficult to …........................... Physics is both significant and influential, in part because advances in its …........................... have often translated into new technologies, but also because new ideas in physics often resonate with other sciences, mathematics, and philosophy. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products which have dramatically transformed …........................... society, such as television, computers, domestic …..........................., and nuclear …...........................; advances in thermodynamics led to the development of motorized transport; and advances in mechanics inspired the development of calculus. 2) THE RIGHT OPTION Chemistry is the science of matter and the changes it undergoes / suffers. The science of matter is also known / addressed by physics, but while physics takes a more general and fundamental approach / approximation, chemistry is more specialized, being set / concerned with the composition, behavior, structure, and properties of energy / matter, as well as the changes it undergoes during chemistry / chemical reactions. It is a physical science which studies of various atoms, molecules, crystals and other aggregated / aggregates of matter whether in isolation or combination, which incorporates the concepts of energy and entropy in relation to the spontaneity of chemical processes. The branches of Chemistry are: analytical chemistry (the study of material samples / matter portions to obtain their compositions), organic chemistry (carbon / silicon based compounds), inorganic chemistry (noncarbon based compounds), biochemistry (the study of substances found in biological animals / organisms), physical chemistry (the study of atoms and chemical systems from a physical point of watching / view) and industrial chemistry (the manufacturing of chemicals in a big scale). Many more specialized disciplines / studies have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system.

Write in English: 1) FÍSICA 2) PROPIEDADES 3) CONVERSIÓN 4) CIENTÍFICO (N.) 5) PRESIÓN 6) ERROR 7) NOTACIÓN 8) MEDIR 9) SIGNIFICATIVA 10) MATERIA 11) VOLUMEN 12) INVESTIGACIÓN 13) POTENCIA