ear 10 Additional Science Holiday Homework

1) What are the two common isotopes of chlorine made up of?

There are two types of chlorine atom- one has 17 protons and 18 neutrons(and so has a relative atomic mass of 35) and the other has 17 protons and 20 neutrons(and so has a relative atomic mass of 37).

2) Why was the Haber process such an important invention?

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Fritz Haber was a German chemist, who received the Nobel Prize in Chemistry in 1918 for his development of synthetic ammonia, important for fertilizers and explosives.

The Haber process is the reaction of nitrogen and hydrogen, over an iron catalyst to produce ammonia.

The Haber process is important sue to the fact ammonia is difficult to produce, on an industrial scale.

The Haber process now produces 100 million tonnes of nitrogen fertilizer each year.

1% of the world's annual energy supply is consumed in the Haber process and that fertilizer is responsible for sustaining 40% of the Earth's population.

3) Find 3 exothermic and 3 endothermic reactions not mentioned in the textbook?

An exothermic reaction is one that releases heat.

Examples of exothermic reactions:

* Adding concentrated acid to water.

* Nuclear fission.

* Condensation of rain from water vapour.

The word endothermic describes a process or reaction that absorbs energy in the form of heat.

Examples of endothermic reactions:

* Evaporation of water.

* Melting solid salts.

* Mixing water and ammonium nitrate.

4) Find 2 uses for a thermistor and 2 uses for a LDR. How does the change in their resistance make them suitable for these jobs?

Thermistors can be used as replacements for fuses and as heating elements in small temperature controlled ovens. LDRs are used in street lights and clock radios. Change in resistance makes them suitable for their jobs because they change as the resistance changes- they depend on temperature and light.

5) Find the mains frequency and voltage of electricity in the USA, England and France. What does this mean about the safety of them and how possible it is to use an English hairdryer in these countries?

France= 230 and 50, England = 240 and 50 and the USA= 120 and 60.

This means that it is not safe to use appliances above a certain voltage in that country, and an adaptor must be used if an English hairdryer is to be plugged in.

6) Find out how the lights, sockets and cooker are wired in a house and why they are like this?

The lights are in a radical circuit with junction boxes to aid the switching process. Sockets are either in a radical circuit or a ring. Cookers are on a separate fuse because they draw a larger current.

7) How is a lightning conductor like the earth wire in a plug?

It is the same because like a lightning conductor, the earth wire will conduct any electricity which it comes into contact with to the ground.

8) Who was Geiger?

Geiger was the man who co-invented the Geiger counter which measures the ionising radiation and discovered the atomic nucleus.

9) What evidence was there for the plum pudding model of the atom?

Experiments on the beams of particles in a tube that were attracted to a positive charge showed that they must be negatively charged themselves. Other experiments showed that it would take about 2000 electrons to weigh the same as the lightest atom, hydrogen.

The tiny negatively charged particles were called electrons.

10) What do the hormones insulin and glucagons do?

Insulin converts glucose to glycogen which stops the glucose level form becoming too high, whilst glucagon converts glycogen to glucose to keep your blood sugar levels stable.

11) Find one controversy that is going on at the moment over stem cells. What do you think?

Using embryonic stem cells as a clinical therapy for Parkinson's disease.

I think this is a good idea even though I do not agree with many other stuff that stem cells could possibly be used for as I thin using stem cells to treat Parkinson's disease and also Alzheimer's will benefit countless amount of people.

12) Describe the famous experiment Gregor Mendel did?

Gregor Mendel was a monk who did an experiment on cross-breeding different types of peas to find out that offspring inherited characteristics in clear and predictable patterns. This helped develop the idea of genes and genetic material.

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